detection of specific food allergens in processed food ... · 1.2 food allergy and food intolerance...

GHENT UNIVERSITY FACULTY OF PHARMACEUTICAL SCIENCES

Department of Bioanalysis

Laboratory of Food Analysis

Academic year 2015-2016

DETECTION OF SPECIFIC FOOD ALLERGENS IN PROCESSED FOOD

PRODUCTS WITH Q-PCR AND ELISA

Mohamed BENCHAIB

First Master of Pharmaceutical Care

Promoter

Prof. dr. De Saeger

Commissioners:

Dr. Isabel Taverniers

Dr. Marthe De Boevre

COPYRIGHT "The author and the promoters give the authorisation to consult and to copy parts of

this thesis for personal use only. Any other use is limited by the laws of copyright,

especially concerning the obligation to refer to the source whenever results from this

thesis are cited."

May 31, 2016

Promoter Author

Prof. Dr. Sarah De Saeger Mohamed Benchaib

ABSTRACT

Food allergies are a worldwide problem. Up to 5% of the world population has a

food allergy. Epidemiological studies reveal that the prevalence of food allergies is still

increasing, especially peanut and tree nuts allergies. The symptoms of a food allergy are

often mild, with some respiration problems, rash, gastrointestinal symptoms as best

known characteristics. Nevertheless, mortality cases are not excluded. Because of the

possible life-threatening consequences, the international food authorities require

labelled food products. The terms of these labels are well defined in regulations.

Fourteen ingredients must be mentioned on the label if present in the food product. Still,

30-40% of the food recalls are due to undeclared food allergens. To detect the allergenic

ingredients, sensitive, specific and reliable techniques are required. In food companies

ELISA tests and other quick detection methods are often used to identify food allergens.

PCR-based methods form a good alternative thanks to their high specificity.

Nevertheless, false positive results are not always excluded. Therefore, optimization of

the existing methods and development of new methods to detect allergens are required.

In 2014 and 2015 some food products containing spices, were recalled from the

market place. Peanut and/or almond were detected in these food products. In the first

part of this study, we wanted to clarify the question: does the recalled product

“chilipepper powder” contain peanut traces, or is the detected signal due to cross-

reaction from the matrix with the used detection method? For this purpose, bell/chili

peppers were tested with a commercial ELISA kit, Ridascreen FAST Peanut, in addition to

a peanut-specific real-time PCR, in order to test for possible aspecific reactions or cross-

reactions from the ELISA/qPCR methods in the matrix (pepper).

In the second part of this study a flour matrix, in-house spiked with 9 different

nuts, was subjected to different ELISA methods to test (1) the sensitivity of the test

methods, by means of a ppm dilution series of the nuts in the flour, and (2) the specificity

of the selected methods. In other words: Are the tested ELISA kits as sensitive as they

prescribe on the one hand, and do they show possible false positive results for other nuts

than they describe on the other hand?

SAMENVATTING

Voedselallergieën zijn een wereldwijd probleem. Tot 5% van de wereldbevolking

lijdt aan een voedselallergie. Epidemiologische studies tonen aan dat de prevalentie van

voedselallergieën nog altijd stijgt, vooral de pinda en boomnoten allergieën. De

symptomen van een voedselallergie zijn vaak mild, met ademhalingsproblemen, uitslag

en maag- en darmklachten als bekendste kenmerken. Toch zijn sterftegevallen niet

uitgesloten. Omwille van de mogelijke levensbedreigende gevolgen, eisen de

internationale instanties etikettering van de voedselproducten. De

etiketteringsvoorwaarden zijn te vinden in wetgevingen. Veertien ingrediënten moeten,

indien aanwezig in het voedselproduct, vermeld worden op het etiket. Maar nog altijd

zijn 30-40% van de teruggeroepen voedselproducten op basis van niet vermelde

voedselallergenen. Sensitieve, specifieke en betrouwbare technieken zijn vereist om

ingrediënten van allergene afkomst op te sporen. In voedselbedrijven zijn ELISA tests en

andere snelle detectiemethodes vaak gebruikt om voedselallergenen op te sporen. PCR-

gebaseerde methodes zijn goede alternatieve technieken dankzij hun hoge specificeit.

Desondanks zijn vals positieve resultaten niet altijd uitgesloten. Daarom zijn optimalisatie

van de bestaande methodes en ontwikkeling van nieuwe allergeendetectie methodes

vereist.

In 2014 en 2015 zijn sommige producten, die kruiden bevatten, teruggeroepen

van de markt. Pinda en/of amandelen werden gedetecteerd in deze voedselproducten.

In het eerste deel van deze studie, willen we een antwoord bieden op de vraag: bevat

het teruggeroepen product “chilipepeper poeder” sporen van pinda, of is cross-

reactiviteit van de matrix met de gebruikte detectiemethode de oorzaak van het

gedetecteerde signaal? Voor deze doelstelling werden paprika’s en chilipepers getest

met een commerciële ELISA kit, Ridascreen FAST Peanut, naast een pinda specifieke real-

time PCR, om mogelijke aspecifieke reacties of cross-reacties van de ELISA/qPCR

methodes in de matrix(peper) te testen.

In het tweede gedeelte van de studie werd tarwemeel, intern gespiked met 9

soorten noten, onderworpen aan verschillende ELISA-methodes om (1) de sensitiviteit

van de geselecteerde test methodes, via een ppm verdunningsreeks van de noten in de

bloem, te testen samen met (2) de specificiteit van de geselecteerde methodes. Met

andere woorden: Zijn de geteste ELISA kits enerzijds even gevoelig als beschreven en

vertonen ze anderzijds mogelijke valse positieve resultaten voor andere noten.

ACKNOWLEDGEMENTS

First of all, I would like to thank my promotor Prof. Dr. S. De Saeger and The Institute of Agriculture and Fisheries Research to give me the opportunity to write this Master thesis. Secondly, I want to thank my experimental mentor Dr. Ir. I. Taverniers helping and guiding me through this project. Answering my endless questions, correcting my thesis and being a true support. Furthermore, I have to mention the laboratory assistants M. Dhondt, A. Staelens and J. Baert. They helped me anytime I needed them with the practical side of my Master thesis. At last, I may not forget the encouragement of my parents. They always push me whenever it’s necessary a little bit further than my limits. My brothers and sister were helping them to making me happier in times it was difficult. I want also to give thanks to my friends who supported and assisted me. They created enough amusement to make sure that I was well rested after work. Thank you all!

CONTENTS

LIST OF ABBREVIATIONS 1

1 INTRODUCTION 3

1.1 FOOD ALLERGY 3

1.2 FOOD ALLERGY AND FOOD INTOLERANCE 4

1.3 MECHANISM 5

1.4 DIAGNOSE ANT TREATMENT 6

1.5 PEANUT AND TREE NUTS ALLERGIES 9

1.6 FOOD ALLERGEN REGULATIONS 10

1.7 FOOD PROCESSING 11

1.8 ALLERGEN DETECTION METHODS 12 1.8.1 ELISA 13 1.8.2 PCR 14 1.8.3 Proteomics 18 1.8.4 Other detection tests 19

2 OBJECTIVES 21

3 METHODS AND MATERIALS 23

3.1 BELL PEPPERS AND CHILI PEPPERS 23 3.1.1 Samples and Sample preparation 23 3.1.2 DNA extraction 24 3.1.3 DNA concentration measurement 25 3.1.4 Real-time PCR for peanut 26 3.1.5 ELISA for peanut 27

3.2 FLOUR SPIKED WITH 9 DIFFERENT NUTS 28 3.2.1 Samples and sample preparation 28 3.2.2 PCR for Pecan and Brazil nut 29 3.2.3 ELISA for 7 nuts 30 3.2.4 Modification of the experimental set up of ELISAs for peanut and hazelnut 31

4 RESULTS 32

4.1 BELL PEPPERS AND CHILI PEPPERS 32 4.1.1. DNA from bell peppers and chili peppers 32 4.1.2 PCR detection of peanut in pepper 35 4.1.3 ELISA detection of peanut in pepper 36 4.1.4 ELISA detection of peanut in rice 37

4.2 FLOUR SPIKED WITH 9 DIFFERENT NUTS 37 4.2.1 DNA concentration measurement and qPCR inhibition test 37 4.2.2 qPCR detection of pecan in flour 38

5 DISCUSSION 40

5.1 BELL PEPPERS AND CHILI PEPPERS 40

5.2 FLOUR SPIKED WITH 9 DIFFERENT NUTS 42

6 CONCLUSION 43

7 ANNEX 45

1

LIST OF ABBREVIATIONS

°C: degree Celsius

µL: microlitre

APC: Antigen Presenting Cells

CFIA: Canadian Food Inspection Agency

Cq: threshold of quantification cycle

Ct or Cp: threshold cycle

DBPCFC: Double Blind Placebo Controlled Food Challenge

ddPCR: digital droplet PCR

dNTPs: desoxyribonucleotides

DSDNA: double stranded DNA

ELISA: Enzyme-linked Immunosorbent Assay

FDA: Food and Drug Administration

FSA: Food Standards Agency

g: gram

GI: gastrointestinal

GMO RM: Genetically Modified Organisms Reference Material

IPC: internal positive control

LC-MS/MS: Liquid Chromatography-Mass Spectrometer/Mass Spectrometer

LOD: Limit of Detection

LOQ: Limit of Quantification

m/z: mass-to-charge ratio

MALDI-TOF: Matrix Assisted Laser Desorption/Ionisation-Time of Flight

mg/L: milligrams per litre

2

mg: milligrams

min.: minutes

ml: millilitre

ng/µL: nanogram per microlitre

PCR: Polymerase Chain Reaction

ppm: part per million

PST: Puncture/Prick Skin Test

qPCR: real-time Polymerase Chain Reaction

RAST: Radioallergosorbent Test

rpm: rotations per minute

sec.: second

ssDNA: single stranded DNA

TE: Tris-HCL EDTA

3

1 INTRODUCTION

1.1 FOOD ALLERGY

Food allergy can be described as a hypersensitive adverse reaction of the body to a

food substance, where IgE antibodies play a major role (1). Food allergens like milk, egg, soy,

fish, wheat and even exotic foods like kiwi and papaya can cause a food allergy (2). Most

commonly known are peanut and tree nuts allergies. The prevalence of food allergies is

estimated between two and five percent of the world population (3, 4). It appears that food

allergies are more present in children than adults, with a prevalence about five percent and

even higher. This suggests that when children get older they often outgrow their food allergy

(4). A hypersensitive person who is allergic to a food substance like peanut, will get an allergic

reaction after consuming this substance or food products containing peanut as an ingredient.

There are many adverse reactions due to the consumption of ingredients that can cause food

allergy. These reactions can differ from mild to severe reactions and include clinical disorders

of the gastrointestinal system, the respiratory system and the skin, while anaphylaxis is a rare

adverse reaction. This is the most dangerous adverse reaction; the consequences of which

can be life-threatening (5).

The reason why some people are allergic to specific foods is completely clear. Some

studies suggest that food allergy is genetically transmitted(6). Other studies insinuate that

food allergy is a Western wealth disease, where there are more allergic. They support this

idea by the fact that Western children from Europe and the United States don’t play outside

as much anymore, where their immune system can be triggered by specific substances. This

hypothesis can as well be strengthened by the fact that we see more allergic people

nowadays than twenty years ago. Adverse parties counter this hypothesis by saying there is

more awareness among the people these days and more means that can detect food

allergies. It’s also true that children’s immune system and gut barrier is not well developed

at young age. In case of the gut flora, new-born mice kept in a germ-free environment are

not having a normal tolerance. So they assume that the prevalence of food allergy is not

increasing the past few years. It’s the attention towards it and the means researching food

allergies that are increased (3).

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1.2 FOOD ALLERGY AND FOOD INTOLERANCE

The words food allergy and food intolerance are commonly confounded with each

other. This isn’t strange because both diseases lead to the same symptoms, when eating a

food substance there occurs an adverse reaction. The difference is that food allergies are

immune-mediated and most of these allergies are IgE-mediated. Food intolerances are not

immune-mediated and have or an enzymatic or a pharmacologic or even an undefined cause.

In Fig. 1 the taxonomy of adverse reactions used in Europe is illustrated. In the US, no

difference is made between toxic and non-toxic adverse reactions. A well-known example of

food intolerance is lactose intolerance.

Figure 1: Classification of adverse food reactions in Europe (7)

The difference between milk allergy and lactose intolerance is difficult to distinguish

at first sight, as the symptoms are the same. However, if there are IgE-antibodies present in

the blood, it’s about milk allergy. But when the enzyme lactase is deficient or even absent,

food intolerance can be assigned as disease form (7).

5

1.3 MECHANISM

As mentioned above IgE-antibodies are related with food allergies. An allergen has

the ability to sensitize the immune system creating IgE-antibodies having a high-affinity for

this allergen (8). Sensitization can be described as the interactions between an allergenic

(food) protein and cells of the immune system: Antigen Presenting Cells (APCs), T-cells, B-

cells. Before the systemic immune system reacts to the allergic food proteins, the physical

gut barrier will trap big food proteins to enter the human blood vessel system. Normally, the

body develops a tolerance against these food proteins, where intestinal epithelial cells and

gut flora play both a major role. Intestinal epithelial cells belong to the APCs, they present an

antigen to T-cells and if the T-cells produce a second signal that triggers the T-cells to

maturate the result of this process is that B-cells will be excited and produce antibodies which

will induce inflammatory responses. When the second signal lacks, there are no antibodies

produced and tolerance is developed (3).

When allergens are presented for the first time to an allergenic individual, no IgE-

antibodies will be produced. IgE-antibodies are attained by a second exposure to allergens.

This is realised by the class-switching of the B-cells. IgE-antibodies are then produced by the

B-cells instead of IgG-antibodies. The IgE-antibodies bind then with mast-cells. Allergens, the

antigens, will on their turn bind with the IgE-antibodies. The part of food (glyco)proteins

responsible for the interaction with IgE-antibodies are called epitopes. Earlier studies say that

epitopes can be either linear or can be conformational. But now, by the information of

crystallography, it’s more obvious that (glyco)protein epitopes are all conformational. This

can be proved by observing and comparing a free peptide with a peptide as a part of the

antigen. A free peptide has a weaker bound with an antibody than a peptide as a component

of a complete antigen (9).

The cross-linking of the antibodies linked to their antigen will eventually trigger the

mast-cells to degranulate. The result of the cell lysis is the release of inflammatory mediators,

like histamine and cytokines. These will affect the GI-tract, the airways and the blood vessels.

Increased fluid and mucus secretion, decreased airway diameter, increased blood flow and

permeability are characteristics of an allergic reaction. There are acute allergic reactions and

late phase reactions. It’s known that histamine plays a major role in the acute phase reaction.

6

Cytokines, chemokines and leukotrienes on the other hand have an important

influence on the late phase reactions. The acute response appears within a few minutes and

disappears as well in a few minutes. On the contrary a late response occurs after hours and

is less wide spread than the acute response. The recovery is also a slow process (11).

Cross-reactions make the mechanism of allergenic reactions even more complicated.

When a person is allergic to a substance, reacting the same way to another substance is

sometimes possible. This can be declared by homologous proteins which mean that they have

identical domains. These domains can bind with the same antibody. Ara h8 is an example of

this aspect, this peanut protein is a homologous of the Bet v 1 protein present in birch pollen.

Sooner or later, they activate the same antibodies leading to the same symptoms (9, 10).

1.4 DIAGNOSE ANT TREATMENT

Diagnosing a person with a food allergy encounters many different methods. First, the

examination of the patient and the evaluation of his medical history can already give an idea

that a food allergy is present. If an acute reaction like acute urticaria; a skin disorder or in the

worst scenario an anaphylaxis occurs, the patient can be questioned what he has eaten in

the few past hours. It has to be noted that not only food can trigger an allergic reaction.

Animals, dust, pollen… can also provoke an allergic reaction. Secondly, when the thought

arises that the symptoms are caused by intake of a food substance, a laboratory evaluation

could distinguish between an IgE-mediated reaction and non-immune mediated reaction by

looking at the IgE-antibody level in the blood. Therefore, the Radioallergosorbent Test (RAST),

is an ideal method. This test detects the blood level of IgE antibodies. As earlier mentioned

IgE-antibodies are correlated with an allergic reaction. The Prick/Puncture Skin Test (PST),

also an IgE-antibody-based test, uses dilutions of the possible allergen. When these dilutions

are applied on the skin and a reaction occurred which is well distinguishable from the

negative control, a food allergy can be suspected. But restriction of these tests, the fact that

a high IgE-antibody blood level does not always indicate a food allergy, can exist (11).

7

Oral food challenge, also called the DBPCFC, the double blind placebo controlled food

challenge, is considered as golden standard for the diagnose of a food allergy. Forasmuch the

name claims, individuals are followed by investigators in a strict nutritional therapy, to

exclude as much as possible confounding factors; like medications. Food granted allergic for

a person is prepared to be unrecognizable for the patient. Therefore, food is being pulverized,

freeze-dried and put in the microwave. But then there is still the presence of the typical

flavour of the food. By using vehicles, commonly capsules for the food substance and the

controls more objective results can be obtained (12, 13).

A new diagnostic tool, ImmunoCap ISAC, the microarray-chip with more than fifty

purified food allergens can also be used as a novel diagnostic tool for food allergies. A major

advantage is that the amount of serum necessary for this tool is very small in order that this

test is an ideal method for diagnosing food allergy in babies/little children. The quality of this

test increases when multiple allergens can be distinguished at once. This tool has a

comparable or even higher efficiency than the existing diagnostic tools, like PST and

ImmunoCap test (Fig. 2), the precursor of the ImmunoCap ISAC test (14).

Figure 2: Principle of the ImmunoCap test (42)

8

Once allergic always allergic? No, there are examples whereat allergic children

outgrow their food allergy. Cow’s milk allergy, mostly present in babies not older than one

year, is an illustration of this outgrowing phenomenon. Eighty percent of the children will

outgrow this intolerance at the age of five. Even cases outgrowing peanut allergy in children

are known. Up to twenty percent of the children will develop tolerance against peanut allergy

(3).

A food allergy treatment does not exist yet. Individuals suffering from food

hypersensitivity are advised to avoid food with ingredients causing the symptoms.

Medication used against food allergies are H1 antihistaminics, asthma medications, steroids.

These medications work not directly on the cause of the allergy, the proteins of the food

substances, but enlighten the appearing symptoms. In case of a prehistory of an anaphylactic

shock reaction as a result of food proteins, precaution is an important part of the food

management. Prescription of epinephrine and the training of using this medication are also

of great importance to avoid any greater complications (15).

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1.5 PEANUT AND TREE NUTS ALLERGIES

Two of the major components in food products that can cause food allergy are

peanuts and tree nuts. Around six percent of the world population suffers from a food allergy.

About 0.6 percent has a peanut allergy and 0.5 percent has a tree nuts allergy. Both form the

main allergen groups causing food allergies in adults. In children, milk and egg (allergens) are

the most common products or ingredients causing food allergies followed by peanut. The

prevalence of peanut allergy has already doubled in young children the past few years(3, 16).

Table 1. Well-known nuts causing food allergies

Peanut generally causes more severe adverse food reactions than any other food

substance like tree nuts, eggs, milk. Anaphylaxis is also more common in patients with peanut

allergy. A study claims that anaphylaxis is also triggered by other co-factors. Asthma is an

example of these co-factors. Of the highest concern is the death as a consequence of a food

allergy. Fifty percent and more of the deaths due to food allergies are cases whereby peanut

is been taken in (15).

Peanut proteins Ara h1, Ara h2 and Ara h3 are considered to have an important role

in peanut allergy. Ara h1 was the first allergen acknowledged as the major peanut allergen.

Ara h3 was identified as another major allergen. Ara h2, maybe the most important allergenic

protein was granted to have more influence on the human body than the other proteins. This

was based on the higher resistance ability of the epitopes of Ara h2 to gastric enzymatic

reactions. These findings could suggest that Ara h2 is the most important peanut protein

affecting the human body which results in allergic reactions (17).

Peanut Arachis hypogaea

Pecan Carya illinoiesis (Wangenh.) K. Koch

Brazil nut Bertholletia excelsa

Hazelnut Corylus avellana

Walnut Juglands regia

Macadamia nut Macadamia ternifolia

Cashew Anacardium occidentale

Almond Amygdalus communis L.

Pistachio Pistacia vera

10

The cross-reactivity in detection methods between peanut and derivative products of

spices were recently detected in Europa and North-America. The Food Drug Administration

(FDA), the Food Standards Agency (FSA), the Canadian Food Inspection Agency (CFIA) recalled

these products after obtaining positive results for the presence of peanut and/or almond.

The national authorities also warned the public about these findings and recommended

individuals with peanut or tree nuts allergy to be alert by reading the ingredients panel, to

avoid ground cumin and seasoning mixes and seek immediate medical care when symptoms

occur. Recalling food products which already are on the marketplace happens frequently.

(Contaminated) foodstuffs with undeclared food ingredients which have to be mentioned on

the label and bacteria in food products belong to the most recalled food products of the

market (42-46).

1.6 FOOD ALLERGEN REGULATIONS

In the food industry it’s obligatory to mention 14 ingredients if present on the label of

their foodstuffs. These 14 ingredients are considered to likely affect a part of the population,

causing adverse reactions. Because the consequences of these adverse reactions can be life-

threatening, the European Union had to make some directives regarding this matter. The

latest update on regarding certain food ingredients is The Commission Directive 2007/68/EC.

Following ingredients must be indicated on the label: cereals containing gluten,

crustaceans, eggs, fish, peanuts, soybeans, milk, nuts, celery, mustard, sesame seeds, sulphur

dioxides and sulphites at concentrations more than 10 ppm or 10 mg/L, lupin, molluscs. The

category nuts consists of almonds, hazelnuts, pistachio nuts, cashews, macadamia nuts,

Queensland nuts, brazil nuts, walnuts and pecan nuts. Not only the pure form of all these

food ingredients are mandatory to mention on the label, also derivatives of these products

must be indicated. Exceptions on five of these food ingredients are allowed. For example,

“nuts used for making distillates or ethyl alcohol of agricultural origin for spirit drinks and

other alcoholic beverages” (52).

11

In many foodstuffs none of these described ingredients are normally present. Though,

we see that many food labels mention “may contain…”, “made in factory that also handles…”

and “made on equipment that also processes…”. The EU does not require these claims, but

in the food industries they use these claims as a precaution. Now and again, unnecessary

labelling food products with these claims prevents the susceptible customer to purchase a

safe product. Nevertheless, hidden allergens can end up in foodstuffs by cross-contamination

with allergenic ingredients which are also processed in the same factory. Otherwise, not

identifying allergenic ingredients can cause life-threatening situations, even small traces are

unsafe for a very susceptible individual. Therefore, appropriate thresholds for allergenic

ingredients are difficult to determine, considering the varying sensitivity among the allergenic

patients. Hence, reliable, specific and sensitive detection and quantification methods are

necessary to accomplish legitimate labelling of foodstuffs (47).

1.7 FOOD PROCESSING

Most food products nowadays undergo a number of modifications in factories. There

are in general two classes of food processing methods, thermal and non-thermal methods,

which can also be combined. Thermal modifications include heating, frying, steaming, boiling,

blanching etc. Non-thermal adjustments involve using high pressure, enzymatic

modifications, irradiation…

An example of a combination of the two methods is autoclaving, combining heat and

high pressure at once. These adaptions are mainly induced to improve many aspects of the

food, such as the flavour, colour and taste. But they can also be important to the producer,

they can make the food more applicable for further modifications (18).

Considering food allergy, a food process method can be an advantage by reducing the

allergenicity of food proteins. Sometimes the possibility exists to remove entire proteins of

the food products, particularly in case of small proteins. To lose allergenicity denatured

proteins must be achieved. This is feasible by adding solvents, extreme pH conditions, intense

temperatures and high pressure. Peanut proteins, which can cause a food allergy, can be

denatured by frying, roasting, boiling the peanuts.

12

The IgE-level in a peanut allergic person is higher when eating roasted peanuts

comparing with the IgE-level after eating fried or boiled peanuts. High IgE-levels are

correlated with allergic reactions. Frying and boiling lower the allergenic characteristics of

peanut proteins. Especially the Ara h2 and Ara h3 proteins lose most of their allergenicity.

Besides, Ara h1 is a more stable protein even at temperatures of 150°C. After the

denaturation of Ara h1 a second folding of this protein will result in a structured conformation

and will still keep its allergenicity (19). Tannic acid can bind with peanut proteins forming

insoluble complexes resulting in failing the bond with IgE-antibodies (20). An enzymatic

modification such as a treatment with trypsin leads to a loss in allergenicity of Ara h1 and Ara

h3. When adding an autoclaving step after the trypsin treatment a higher loss of the

allergenicity was achieved (21).

Tree nut proteins show the same sensitivity to thermal and non-thermal modifications

as peanut proteins. It has been described that the allergenic proteins of almond, walnut and

cashew are not stable when these nuts are treated non-thermally such as a γ-irradiation

treatment. Also thermal treatments show a decrease in the stability of the nuts. Brazil nut

and pecan are also responsive to thermal treatments and enzymatic proteolysis (18).

1.8 ALLERGEN DETECTION METHODS

Because of the upcoming food allergies and their complications, the food industries

are submitted to strict regulations as mentioned above. To detect any potential allergen in

the produced food products, they rely on specific methods for detection that are available

on the market or are designed within the firm. Test procedures which can be performed in a

short time are preferred. Enzyme-Linked Immunosorbent Assays (ELISAs), lateral flow tests

and dipsticks are very popular tests to obtain the first information about the presence of an

allergic substance. Besides ELISA, Polymerase Chain Reaction (PCR)-based methods can be

performed in second instance to have more certainty about the allergen. (Semi)-

quantification of the allergen can be realised with ELISA- and PCR-based methods.

13

1.8.1 ELISA

Enzyme-Linked Immunosorbent Assays are accepted as first choice methods to detect

allergens. Many reasons contribute to this. First of all, these assays do not need many

apparatuses. Secondly, an ELISA is a fast method to obtain results in short time which is

necessary in food industries. It has high sensitivity and specificity for detecting allergens.

Different types of ELISA exist (23). The simplest format of ELISA is a plate coated with

antibodies. The protein solution that consists the antigens is then added. The antigens bind

with the antibodies and the remaining binding sites of the antibodies are blocked with

another protein, often serum bovine is used in this step. Then other monoclonal antibodies,

which also recognize the antigens, are added. These antibodies are linked with an enzyme.

After a washing step, a substrate for the enzyme is added and creates a colour density which

can be measured by a fluorimeter(22). A more complex, but often used ELISA method is the

sandwich ELISA (48). See Fig. 3.

Figure 3: Sandwich ELISA

(1) Wells are coated with an antibody. (2) Sample with antigen is added and binds if recognized by

the antibody. (3) Detecting antibody with affinity for the antigen is then added. (4) An enzyme-linked

antibody which recognizes the detecting antibody from the previous step is added. (5) A substrate is

added and converted by the enzyme from the previous step to a detectable structure (49).

14

1.8.2 PCR

Polymerase Chain Reaction is a DNA-based method. Where ELISA focuses on the

protein itself, PCR will search for DNA sequences which eventually translate into this protein.

After extracting the DNA from the food sample, two short oligonucleotide sequences, also

called primers, are added to bind to their complementary target sequences. PCR exists of

some sequential steps. First, the DNA strands need to divide, this happens at the

denaturation temperature of DNA. Often a temperature of 95°C is used. Second, the

temperature is decreased to about 55-65°C, the added primers can now anneal to the

recognized sequences that translate for the antigen. After elongation with a polymerase-

enzyme of the primers with added oligonucleotides, at a standard temperature of 72°C,

copies of the target DNA are formed. The denaturation-annealing-elongation process is

repeated 30-35 times, to assure enough copies of the target DNA are formed. After the third

cycle normally the target DNA is already copied. To visualize these components labelled

primers can be used (24).

To analyse the formed PCR products, gel electrophoresis can be used. Gel

electrophoresis uses a standard DNA ladder to compare the PCR products with. A well-known

used dye is the SYBR Green dye, which makes visualisation possible of the PCR products. The

gel in this system is often made of agarose. The DNA fragments achieved in the PCR can be

put in the gel in separately. Then an electric field is developed, the negative DNA fragments

move from the positive side to the negative side of the agarose gel, which is put in a buffer.

Small PCR products will move faster than the larger products. Eventually, the length of the

PCR products can be traced. Identification of the formed DNA fragments can be realised by

adding a restriction enzyme that recognizes a site on the target DNA (25).

15

Real-time PCR or also called quantitative PCR(qPCR), is another method based on the

principles of PCR itself. The main advantage of this method is its higher sensitivity. Only a tiny

amount of the PCR products is needed to have results with this method. Real-time PCR

follows the amplification of the DNA in time and already in the beginning of the exponential

phase, the phase where the first copies are formed, detection is possible. This is illustrated in

Fig. 4. Other advantages are the reduced bench time and the risk of contamination that is

diminished (26).

Figure 4: Amplification curve of a positive sample (50)

Qualitative and quantitative results can be achieved by using real-time PCR. When the

fluorescent signal crosses the background signal i.e. the threshold line, the threshold cycle (Ct

or Cp) or the cycle of quantification (Cq) is reached. From this point, an accumulation of the

fluorescent signal is associated with an exponential amplification of the DNA with the allergen

specific primers. A steady phase is reached when no single stranded DNA fragments can be

duplicated.

For quantification of the DNA, standard curves are set up with known DNA

concentrations. Each standard has its own Ct value. The higher the DNA concentration, the

lower the Ct value. A linear liaison is observed between Ct values and the logarithmic

concentration of the DNA. Using this curve, the DNA concentration of the sample of interest,

after real-time PCR, can be identified by analysing which logarithmic DNA concentration

corresponds with the Ct value of the sample (27, 28).

16

Figure 5: Fluorescence mechanism by using a hydrolysis-based probe (51)

The detection of the amplification products is based on fluorescence. The use of a

hydrolysis-based probe is a regularly applied method. The single stranded DNA probe

hybridizes with a sequence between the two primers. At one end of the probe a nucleotide

is labelled with a fluorescent marker, another nucleotide of the probe is labelled with a

quencher. The function of the quencher is to absorb the fluorescence signal emitted by the

fluorescent marker. When the DNA polymerase enzyme adds new nucleotides to the primers,

at a certain point the probe will normally obstruct the further amplification. But the DNA

polymerase enzyme has an extra exonuclease function which disassembles double stranded

DNA in its path. The nucleotides of the probe will all be replaced. The nucleotide with the

quencher is no longer at a close distance to the fluorescent marker. This makes it possible for

the fluorescent marker to emit a signal (29). This mechanism is illustrated in Fig. 5.

It is important to mention that the presence of PCR inhibitors is not a rare

phenomenon in real-time PCR. False negative results are possible when these inhibitors are

present. These inhibitors can bind to single stranded or double stranded DNA, obstructing

the amplification of the antigen sequence. Inhibition of the polymerase enzyme can also

appear. Magnesium, a very important co-factor of the polymerase enzyme, can interact with

a PCR inhibitor resulting in blocking the formation of the amplicons.

17

Known PCR inhibitors are myoglobin, urea, proteinases, polysaccharides, ethanol,

phenol. The use of an IPC, internal positive control, can rule out the presence of a PCR

inhibitor. In the same reaction mix, second primers and probe are used to detect a control

sequence. When the control sequence is amplified, but the target amplicon is absent, this

indicates that the PCR reaction was not blocked by any inhibitors. If the target DNA fragment

is not formed and the control sequence is not amplified, PCR inhibitors could have caused

these reaction failures (30-34).

More and more applications are published of the digital droplet PCR (ddPCR). This

method has a higher sensitivity than real-time PCR. Even the quantification of a DNA sample

concentration can be realised without using calibration. The PCR mix, which contains MgCl2,

a thermostable polymerase enzyme, a forward and reverse primer, a probe and

desoxyribonucleotides (dNTPs) for the amplification of the added DNA, is now partitioned

into thousands of droplets by using a water-oil emulsion. The PCR process of denaturation-

annealing-elongation is now applied on each of these droplets. The following step, the

detection is comparable to the detection in the real-time PCR. Measuring the fluorescence of

each droplet can predict the presence of the target DNA. At the end an estimation of the

concentration of the target DNA can be made. The difference between positive and negative

droplets is not always evident. PCR disturbing factors such as PCR inhibitors and delayed PCR

onset can also appear. Working on a microscale is very cost efficient, but mistakes are not

excluded. Within the process damaged droplets could give false positive and false negative

results. False positives will emit a higher fluorescence signal; false negative droplets will emit

on their turn a reduced signal. All these factors, which impede the correct analysis of the

DNA, are called “rain”. “Rain” is the cause of incorrect determination of concentration

thresholds(35). Optimization can be realised by little variations in the temperatures of the

PCR process, by variations in the concentrations of the used primers and/or probe(36). Also

enzymatic restriction of the DNA, can contribute to more accurate quantification of the

DNA(37). Because of the many advantages, ddPCR has been recommended to certify

Genetically Modified Organisms Reference Materials (GMO RM) (35).

18

1.8.3 Proteomics

Liquid chromatography linked to a tandem of mass spectrometry (LC-MS/MS) is an

upcoming method to detect food allergens. LC-MS/MS is less time-saving than PCR of ELISA

methods but delivers more reliable results. It does not deal with indirect protein or species

DNA identification as ELISA and PCR methods are based upon. In practice the search of

conserved peptides present in original and processed food material is the aim of this method

(38).

Because of the complexity of food proteins, prefractioning is recommended before

MS analysis. Therefore, 2D electrophoresis is proven to be a useful method. Proteins are

separated according to their iso-electric point and their molecular weight. These proteins are

then subjected to a protease treatment often with the trypsin enzyme. After the digestion

step the peptide scan be identified with a mass spectrometer.

Usually the protein identification is achieved by MALDI-TOF. A laser collides on the sample

creating ionized peptide samples. These peptides travel through a tube and in function of

their times of flight a m/z ratio can be set up. Every m/z ratio with its intensity can be assigned

to a peptide (39).

A better prefractioning method is liquid chromatography. This strategy can be used

to identify the proteins in a straight approach from the complex mixtures when coupled with

a mass spectrometer. To accomplish more reliable results and a higher specificity MS tandem

mode can be performed. The ionized peptides are passing components which select specific

ions for the next MS. These ions are then delayed in speed, fragmented again and then re-

accelerated before they enter the next mass spectrometer. A LC-Q/TOF MS/MS already

shown its utility by monitoring the peanut proteins Ara h1, Ara h2 and Ara h3.

It has to be mentioned that adequate stable peptides are preferred to avoid the effects of

processing (40).

19

1.8.4 Other detection tests

Lateral flow assays (LFAs) and dipsticks are in addition to the ELISA method also quick

screening methods popular in the food industries. In contrast with the earlier described

methods, these tests give more qualitative than quantitative results. In food industries they

are one of the ideal first test methods to search if any ingredient, that causes an allergy, is

present in the produced food product.

Lateral flow devices and dipsticks are actually a simplified form of an ELISA. They are

up to three times faster than a classical ELISA test. The best know lateral-flow assay is the

pregnancy test. In 1997, the first LFA for peanut was invented. Now, a rapid evolution shows

up, more and more LFAs and dipsticks are developed for detecting food components. Fig. 6

represents the different areas on a lateral-flow assay. A lateral-flow assay consists of four

compartments. The test sample is applied onto the first compartment. Capillary forces help

then move the test sample along the other three compartments. The next compartment

incorporates antibodies which can recognize the target allergen.

Figure 6: Compartments of a lateral-flow test (41)

20

These antibodies are usually conjugated with colloidal golden nanoparticles. Further

you have the test line, which onto other antibodies are fixed. The antibodies can recognize

another part of the target allergen. A positive lateral-flow test gives a coloured test line and

a coloured control line. The coloured test line consists of two sort of antibodies, one which is

conjugated with the target allergen and the golden nanoparticles and another which binds

the previous complex making the test line visible. The control line, the third compartment,

rules out false negative results. To obtain a reliable result, the control line has to be coloured.

False negative results can be caused by inefficient capillary forces. So, the test sample with

the target allergen can’t reach the test line and control line. The control line onto which

species specific antibodies are attached is then also not coloured, indicating the test

procedure has to be repeated. At the end, an adsorbent pad collects then the rest of the test

sample (41)

21

2 OBJECTIVES

In 2014 and 2015, in Europe, the United States of America and Canada, certain food

products tested positive for undeclared peanut and/or almond traces. It was remarkable for

the FSA, FDA and CFIA that all these food products contained spices. In the UK, a spice mix

which was used in three food products was presumed to be the reason. The FDA in America

detected undeclared peanuts in products in which ground cumin was processed. In Canada

as well, curry powder products tested positive to undeclared peanut and almond.

In the interest of these findings the first part of this study investigates bell peppers

and chili peppers with ELISA and qPCR (Fig. 7). The purpose was to study the possible cross-

reactivity of different detection methods with bell/chili pepper matrices. Both DNA-based

methods i.e. real-time PCR, as well as protein-based methods i.e. sandwich ELISA method

were used to test this hypothesis. The qPCR and ELISA methods were also tested for their

sensitivity and specificity with pure chili pepper reference material spiked with peanut. DNA

for the qPCR was extracted with two different kits: The NucleoSpin Food kit and the Qiagen

Dneasy Plant Mini kit. The Qiagen method is used as the internal standard kit to extract DNA.

By comparing these kits, the kit which can extract a larger amount of DNA and is easier to

practice with can be determined. Also for the measurement of the DNA concentration two

different methods were applied: spectrophotometric versus fluorimetric measurements. The

aim of this part of the work was to choose the most suitable DNA extraction and DNA

measurement technique for the particular matrix “pepper”.

In the second part of this study, a wheat flour matrix was spiked with eight different

tree nuts and peanut (Fig. 8). A dilution series of all 9 nuts in the flour (from 0 to 100 ppm)

was composed. First aim of this part was to evaluate the sensitivity of the AgraQuant (PLUS)

ELISA kits by using pure nut dilution series. The influence of wheat flour on the sensitivity of

the ELISA kits was a second purpose. The specificity of the ELISA kits was also tested. The last

objective was to evaluate the influence of wheat flour and other nuts on the detectability of

the target nut.

22

Figure 7: Scheme of objectives for the bell/chili peppers

Figure 8: Scheme of objectives for the nuts-in-flour matrices

23

3 METHODS AND MATERIALS

3.1 BELL PEPPERS AND CHILI PEPPERS

3.1.1 Samples and Sample preparation

Nine varieties of the Capsicum annuum-genus (“dolce&piccante”, BLUMEN GROUP

SPA, Milan, Italy) that were freshly harvested were collected (Table 3.1). The seeds and

mesocarp of the bell peppers and chili peppers were separated and stored at -80°C

(Eppendorf Innova Ultra-Low Temperature) (Eppendorf Belgium nv/sa, Rotselaar, Belgium).

Table 3.1 Nine varieties of the Capsicum-annuum genus + pure peanuts

For DNA-extraction ground samples were necessary to obtain homogenous samples.

The seeds were put in a container and treated with liquid nitrogen (Air Lquide Benelux,

Herenthout, Belgium) in order to make them easier to grind. The seed samples were put in

the container, liquid nitrogen was added, when the nitrogen is evaporated, the container was

put in the ball mill Retsch MM400 (Retsch Technology GmbH, Haan, Germany) and then the

time was set on 3 min. and the frequency on 30 times/sec.

The mesocarp of the peppers was already been cut in little pieces with the peal on.

VARIETY NAME ABBREVIATION

Bell Pepper PLANET SEED 1 FLESH 1

Bell Pepper AURELIO SEED 2 FLESH 2

Peperone HABANERO Red Orange SEED 3 FLESH 3

Peperone MECHICO SEED 4 FLESH 4

Peperone YUCATAN SEED 5 FLESH 5

Peperone HABANERO Rosso SEED 6 FLESH 6

JALAPENA SEED 7 FLESH 7

TURKISH Pepper SEED 8 FLESH 8

SPANISH Pepper SEED 9 FLESH 9

Peperone CANCUN SEEDS+FLESH10

Peperone SALTILLO SEEDS+FLESH11

ROASTED PEANUT C+1 C+1' C+1''

SALTED PEANUT C+2 C+2' C+2"

24

The flesh of the mesocarp was ground with a machine (SerCoLab, Merksem, Belgium)

(Fig. 9) after the samples were put in a plastic sack and put a few seconds in liquid nitrogen.

Besides these nine varieties, two extra chili peppers (“dolce&piccante”, BLUMEN GROUP SPA,

Milan, Italy) were harvested and dried at room temperature. Seeds and mesocarp were

ground as one in a blender with a mini container (Waring commercial blender 8011 ES; MC1

Mini Container) (Waring Commercialer, Torrington, USA) to realize homogenous samples.

Afterwards the mixture was ground with the ball mill Retsch MM400 to pulverize the hard

seeds, the time was set on 3 min. and the frequency on 30 times/sec. After the homogenous

samples were ready, these were stored at -20°C (Liebherr LGex 3410) (Liebherr, Liège,

Belgium). Pure peanut samples were acquired from a local store (Colruyt Group, Halle,

Belgium). Reference material of pepper (European Spice Services nv, Temse, Belgium) was

spiked with pure peanut, acquired from a nut stall, using the Ultra Centrifugal Mill ZM 200

(Retsch Technology GmbH, Haan, Germany).

Figure 9: Grind machine

3.1.2 DNA extraction

To assure good quality results in PCR, DNA is first extracted from the samples. This

was assured by using two commercial DNA extraction kits, the Qiagen DNeasy Plant Mini Kit

(Qiagen, Hilden, Germany) and the NucleoSpin Food Kit (Machery-Nagel, Duren, Germany).

The procedure starts with the lysis of the cells together with removing the membrane lipids.

Then proteins are precipitated by using a protease.

25

The RNA is discharged by adding RNase. If contaminants are still present, these can be

removed by the silica columns present in the DNA extraction kits.

For the Qiagen extraction 100 mg sample was needed. DNA extraction on the seeds

could not be set in double due to the tiny amount obtained from the bell peppers and chili

peppers. For the seeds of peperone Habanero Red Orange only 50 mg could be weighed. For

the pulp of the peppers, only a few varieties could be weighed in double, for the same reason

as for the seeds. Some flesh samples contained a lot of peal, but were included anyway in the

test set. According to the protocol of the NucleoSpin Food Kit, 200 mg sample was required.

No seeds of the peperone Habanero Red Orange could be analysed with the NucleoSpin Food

Kit. A negative control, ultra-pure water (Biochrom GmbH, Berlin, Germany) and a positive

control, 400 ppm peanut in pepper, were subjected to these extractions.

3.1.3 DNA concentration measurement

To measure the extracted DNA, two methods were used. A spectrophotometric and a

fluorimetric method were applied. To measure the absorbance, the UV-VIS

spectrophotometer Biospec Nano (Shimadzu Biotech Europe GmbH, Duisberg, Germany) was

used. The fluorescence was measured by the Quantus Fluorometer (Promega Corporation,

Madison, USA).

The spectrophotometer was set to detect dsDNA from the DNA solutions obtained

from the DNA extraction kits. A tiny amount (2 to 5 µL) of the extracted DNA was pipetted on

the reading frame of the Biospec Nano and the path length was set on 0.7 mm.

26

Measuring the DNA extracts was also performed with the Quantus Fluorometer. For

each sample 1 µL DNA was added to 199 µL QuantiFluor, which contain a dye that can bind

with DNA. The solutions were mixed thoroughly and were incubated 5 min. in the dark.

Before measuring the samples, the Quantus Fluorometer was calibrated with a blank and

standard sample. The blank and the standard were prepared as followed. To 199 µL

QuantiFluor was 1 µL TE buffer added. The standard solution was prepared by adding 1 µL

Lambda DNA (400 ng/µL) to 199 µL. These two methods are based on the Beer-Lambert Law:

log I0 / I = ε. l. c

with: I0: intensity of transmitted light

I: intensity of incident light

ε: molar extinction coefficient (𝐿 𝑚𝑜𝑙. 𝑐𝑚⁄ )

l: path length of sample (cm)

c: concentration (𝑚𝑜𝑙 𝐿⁄ )

3.1.4 Real-time PCR for peanut

The used primers and probe were based on the study of Bergerova et all.,2011. The

peanut specific primers Ara h3 Forward and Ara h3 Reverse (Integrated DNA Technologies,

Leuven, Belgium) and peanut specific Ara h3 probe (Eurogentec, Liège, Belgium) were added

to the qPCR reaction mix (5x HOT FIREPol qPCR Mix Plus) (Bioconnect, Huissen, Netherlands).

The reaction mix also contained DNA, thermostable HOT FIREPol DNA polymerase, dNTPs,

MgCl2 and ultra-pure Water. The primer concentrations were 7,5 µM and the used probe

concentration was 5 µM. In a volume of 25 µL, the final concentrations of the peanut specific

primers were 300 nM and 200 nM for the peanut specific probe. The SEEDS samples were all

diluted to 40 ng/µL. For the 400 ppm peanut in pepper samples, tested with the SEEDS

samples, a dilution of 40 ng/µL was also evaluated.

27

The conditions for the qPCR for the seeds and mesocarpflesh on the Roche Lightcycler

480II (Roche Diagnostics GmbH, Mannheim, Germany) were based on the data sheet of Solis

BioDyne and were set as follows: initial denaturation at 95°C for 15 minutes, 50 cycles

consisting of denaturation at 95°C for 15 seconds, hybridization and elongation at 60°C for 1

minute. The cooling procedure was managed at a temperature of 40°C for 10 seconds.

3.1.5 ELISA for peanut

A protein-based method is another way to obtain information about the allergenicity

of food substances. But bell peppers and chili peppers contain a lot of polyphenols and

tannins which could inhibit the detection of peanut. Therefore, the protein preparation starts

with adding skim milk powder. Casein, a protein isolated from milk powder, has a high affinity

for polyphenols and tannins. That means that as an effect of the addition of skim milk powder,

more target proteins will bind with the antibodies attached in the wells.

The Ridascreen FAST Peanut (R-Biopharm AG, Darmstadt, Germany) is a sandwich

ELISA which can detect peanut specific proteins. Detection of Ara h1 and Ara h2 is achieved

with the use of polyclonal antibodies of this ELISA test. The limit of detection (LOD) and the

limit of quantification (LOQ) of the Ridascreen FAST Peanut are respectively 1.5 ppm and 2.5

ppm. Different tree nuts like hazelnut, pecan, almond, walnut, cashew and pistachio show no

cross-reaction with this test. Also, other food substances such as corn, wheat, sesame or soy

do not interfere with the assay. Only cross-reactivity with chickpea (0.2%) and green pea

(0.001%) can be observed.

The samples underwent a sample preparation as followed. Some samples, only 200

mg was available. For all the SEEDS samples 200 mg was used for the ELISA test, 200 mg of

skim milk powder which was manufactured in the Food Pilot division of ILVO (ILVO 370, Melle,

Belgium) was added. Then 4 ml diluted extraction buffer (60°C) was added. For Peperone

HABANERO Red Orange, no seeds were available for the ELISA test. For JALAPENA, enough

sample material was available to evaluate the adapted procedure with the prescribed one.

28

As regards the FLESH samples, for Peperone MECHICO only 200 mg mesocarp was

available for the ELISA test. For Peperone Yucatan, no flesh was available for the test. For the

samples of which enough sample material, at least one gram, was available,

the procedure prescribed in the Ridascreen FAST Peanut kit was used. Next, the

samples were intensively mixed with the vortex (VWR International nv/sa, Leuven, Belgium).

The alternative procedure was followed by centrifuging 2 ml of the extracts for 10 minutes at

14.000 rpm with the microcentrifuge 5417R (Eppendorf AG, Hamburg, Germany). Hereafter,

the ELISA was performed as described in the protocol of Ridascreen FAST Peanut with the use

of 100 µL of the supernatant. After adding stop solution, the absorbance was measured with

the Fluostar Optima (Isogen Life Science, Temse, Belgium).

3.2 FLOUR SPIKED WITH 9 DIFFERENT NUTS

3.2.1 Samples and sample preparation

Wheat flour was obtained from a local store (Colruyt Group, Halle, Belgium). To this

flour nine different nuts (Colruy Group, Halle, Belgium) were added and homogenized with

the Ultra Centrifugal Mill ZM 200. The eight different tree nuts include pecan, brazil nut,

hazelnut, walnut, macadamia nut, cashew, almond and pistachio. Peanut was also added to

the wheat flour. Afterwards, a dilution series was made of the flour matrix. The final nuts-in-

flour concentrations were: 0 ppm, 1.5625 ppm, 3.125 ppm, 6.25 ppm, 12.5 ppm, 25 ppm, 50

ppm and 100 ppm. The 25, 50 and 100 ppm samples were diluted after the extraction to 20

ppm with TE buffer (Tris-HCL(1M) and Na2EDTA(0.5M) (Sigma-Aldrich, Machelen, Belgium)

because of the quantification limits of the ELISA test kits (Romer Labs Diagnostic GmbH, Tulln,

Austria). For pecan and brazil nut only a qPCR method and no ELISA test kit was available to

detect these nuts in the spiked wheat flour matrices.

29

3.2.2 PCR for Pecan and Brazil nut

The first aim of this part is to examine the flour matrices were examined with different

nut-specific ELISA methods to test for the spiked concentrations as well as the tests’

sensitivities. However, not for all 9 nuts there is an ELISA test available (Table 3.2).

Table 3.2: Available commercial ELISA and qPCR kits for peanut and tree nuts

For two nuts, pecan and brazil nut, qPCR was used to detect the nuts in the matrices.

For the DNA extractions the SureFood PREP Advanced kit (R-Biopharm AG, Darmstadt,

Germany) was used. The extraction protocol of the kit was followed. After the DNA

extractions, half of the eluted DNA extracts were purified with the NucleoSpin Gel and PCR

Clean-up kit (Machery-Nagel, Duren, Germany), such that higher DNA concentrations can be

obtained. A dilution series of the 100 ppm A sample of the spiked flour matrix with

concentrations variating from 0.976463 ng/µL to 500 ng/µL was put in the block cycler to test

if inhibition can take place.

Species

qPCR R-

Biopharm

(SureFood)

qPCR Biotecon

(FoodProof)

ELISA R-

Biopharm

(RidaScreen

FAST)

ELISA RomerLabs

(AgraQuant

PLUS)

ELISA Neogen

(Veratox)

Lateral Flow test

R-Biopharm

Lateral Flow test

RomerLabs

(AgraStrip)

Lateral Flow test

Neogen (Reveal

3-D)

peanut x * x ** x x x x x xhazelnut x * x ** x x x x x x, x°°°pecan x x°°°walnut x * ** x ° x °° x x x°°°macadamia x x x x xpara = brazil x x xcashew x x x x + pistachio x°°°almond x x x x x x x, x°°°pistachio x x x x + cashew x°°°positive

control

material

available

with kit?

NA Allergen RM800 ** NA NA

REMARKS:

NA = not available

* triplex PCR (+ IAC) also exists

** Allergen RM 800

° AgraQuant kit, no PLUS kit

°° BioKits Walnut kit, no Veratox kit

°°° Reveal for Multi-Treenut

Allergen RM 800 is a reference material used for the quantitative analysis of allergens in food samples. It contains celery, soy, peanut, hazelnut, walnut and

gluten in a defined concentration of 800 mg / kg. The reference material is processed in parallel with the food samples, and the extracted DNA is used to

create a standard curve. When used in combination with the foodproof Allergen Detection Kits, quantification of allergenic content in the sample can be

30

The SureFood Allergen ID Pecan kit and the SureFood Allergen ID Brazil Nut kit (R-

Biopharm AG, Darmstadt, Germany) were used to make target reaction mixes and inhibition

reaction mixes. The dilution series samples were thus pipetted in double, once for the

reaction control and once for the inhibition control. The conditions for qPCR were described

in the protocol of the SureFood Allergen ID kits. Initial denaturation at 95°C for 5 minutes,

denaturation at 95°C for 15 seconds and the ‘hybridization and elongation’ step at 60°C for

30 seconds. The cooling procedure was managed at 40°C for 30 seconds. This process was

repeated 50 times.

The purified flour matrices after the PCR clean-up, some pure tree nuts samples

(pecan A and B, walnut A and B, hazelnut B, pistachio B) and peanut B sample which also

underwent the PCR clean-up, were pipetted in the SureFood reactions plate.

3.2.3 ELISA for 7 nuts

For seven of the nine nut types an ELISA method with AgraQuant was possible (Table

3.2). For five tree nuts an AgraQuant PLUS sandwich ELISA method can be performed. Walnut

detection had to be performed with an AgraQuant Walnut sandwich ELISA, whereby the

procedure takes longer than the PLUS kits. One gram from each flour matrix dilution with the

9 different nuts was used. The extractions were examined twice if possible with the ELISA

AgraQuant kits. AgraQuant PLUS Peanut and AgraQuant PLUS almond both have a LOD of 0.5

ppm total nut. The other AgraQuant PLUS kits have a LOD of 1 ppm. The quantitation range

for all the AgraQuant PLUS kits was 1-25 ppm total nut. The AgraQuant Walnut kit has a LOD

of 0.35 ppm and a quantitation range of 2-60 ppm total walnut.

Before the ELISA test, to each sample of one gram, additives 1 and 2 (included in each

kit) were added. Then 20 ml hot, not boiling, water was added to each tube. When the tubes

were shaken until the additive capsules and sample were dissolved, an aliquot of 2 ml was

transferred to a centrifuge tube. After the centrifuging step (12 000 rpm for 5 min.), 150 µL

supernatant was used for the ELISA test. The ELISA test was performed as described under

“Short Instruction” in the protocol. The absorbance was measured with the Fluostar Optima.

31

3.2.4 Modification of the experimental set up of ELISAs for peanut and hazelnut

After carrying out the SureFood qPCR test for pecan, only two different AgraQuant

PLUS ELISA kits were evaluated. Peanut and hazelnut were selected to be the allergens of

choice. The main aim was still to check the spiked concentrations of the different nuts in the

flour, as well as to check the prescribed sensitivities of the kits. However, it was decided to

have a more detailed look into this sensitivity on the one hand, and specificity on the other

hand. For these purposes four different sub-objectives were formulated. To test the

sensitivity of Agraquant PLUS Peanut and AgraQuant PLUS Hazelnut, a dilution series of

peanut, as well as for hazelnut in TE buffer was made (from 0.5 to 20 ppm). The sensitivity of

the kits was also tested in presence of wheat flour. Only pure peanut in flour dilution series

was available (2-4000 ppm), the 20-4000 ppm dilutions were again diluted with TE buffer to

remain in the range of the ELISA kit. No dilution series of pure hazelnut in flour was available.

The sensitivity of the ELISA kits was also tested for peanut and hazelnut in presence of flour

and other nuts. The spiked nut-in-flour dilution series had concentrations from 0 to 100 ppm.

Dilutions of 20 ppm were made from the concentrations 25, 50 and 100 ppm with TE buffer.

For each previous described undiluted samples one gram was necessary for the ELISA kits.

The dilutions with TE buffer were carried out after the protein extraction procedure.

32

4 RESULTS


4.1.1. DNA from bell peppers and chili peppers

DNA was extracted from the peanut in pepper dilution series using the Nucleospin

Food kit. It has to be mentioned that the last step, namely the elution of the DNA was

performed with a four times smaller elution volume (50 µL) than normally described in the

protocol. Afterwards, the DNA concentration was measured with the spectrophotometer

Biospec Nano and the Quantus Fluorimeter. Table 4.1.1 shows the obtained DNA

concentrations, OD A260/A280 ratios and OD A260/A230 ratios peanut in pepper dilution series

samples and the positive control (C1+).

Table 4.1.1 Bell peppers and chili peppers: DNA concentrations, OD A260/A280, OD A260/A230

of peanut in pepper dilution series and pos. control (C+1) after Nucleospin

Weight(mg)Biospec-

NANO(ng/µL)

OD

260/280

OD

260/230

Quantus

(ng/µL)

0 PPM A and B 201 202 373,29 371,3 1,98 1,981,55

1,49268 250

0,5 PPM A and B 201 198 360,33 270,69 1,92 1,921,29

1,27280 269

1 PPM A and B 199 198 327,85 402,66 1,92 1,941,34

1,45281 319

5 PPM A and B 198 202 309,17 291,36 1,92 1,931,29

1,29249 244

20 PPM A and B 200 201 262,37 296,71 1,91 1,911,23

1,33210 248

50 PPM A and B 203 200 328,44 316,14 1,94 1,951,39

1,39258 253

100 PPM A and B 203 199 271,70 278,97 1,91 1,961,19

1,43201 198

400 PPM A and B 201 200 237,80 275,22 1,93 1,921,29

1,32197 193

C+1 measured twice 199 702,64 705,74 2,22 2,222,01

2,02360

H2O 200 2,84 2,2 0,71 0,0096

STD-LAMBDA(QUANTUS, 400 ng/µl) 399

DNA Extraction(PEANUT IN PEPPER)

Nucleospin(200mg)

33

Overall, concentrations were up to 1.5 times higher with the Biospec Nano than with

the Quantus Fluorimeter. The pure peanut DNA concentration pointed a major difference

between the two methods. The Quantus Fluorimeter measured 360 ng/µL, half of the DNA

concentration measured with Biospec Nano. The purity of the DNA extractions could also be

measured with the Biospec Nano. The peanut in pepper samples and the pure peanut sample

showed OD A260/A280 ratios of at least 1.91, indicating no protein contamination occurred

within the DNA extraction procedure. As for other contaminants, the OD A260/A230 ratios of

the samples were considered. None of the peanut in pepper samples had an OD A260/A230

ratio higher than 1.8. For the pure peanut sample 2.01 and 2.02 were measured as the OD

A260/A230, illustrating no organic compounds or chaotropic contaminants were detected.

For the bell pepper and chili pepper samples two DNA extractions were performed

using the Qiagen DNeasy Plant Mini Kit and the NucleoSpin Food Kit. The 400 ppm peanut in

pepper dilution samples also underwent these two DNA extractions. In Table 4.1.2A (see

Annexed) the DNA concentrations, OD A260/A280ratios and OD A260/A230 ratios after both

methods are listed up for the SEEDS samples. Table 4.1.2B shows the negative controls after

both methods. Looking at the measurements of the Qiagen extracts, less major differences

between the spectrophotometric and fluorimetric method were seen. However, it can be

seen that the Quantus Fluorimeter measures almost always lower DNA concentrations,

except for the seeds of Bell Pepper PLANET and SPANISH Pepper. The OD A260/A280 ratio was

for all samples higher than 1.8, except for the seeds of Peperone HABANERO Red Orange an

average optical density of 1.77 was measured. For the OD A260/A230 ratios of the samples,

seeds of Bell Pepper AURELIO, TURKISH Pepper and SPANISH Pepper were higher than 1.8.

The other samples showed a low optical density ratio, implying contamination of these

samples.

After the NucleoSpin extraction, higher DNA concentrations than the Qiagen method

were quantified for six samples with the Biospec Nano spectrophotometer. For Peperone

HABANERO Red Orange, no seeds were available for the NucleoSpin DNA extraction. For the

seeds from Bell Pepper PLANET and SPANISH Pepper, higher DNA concentrations with the

Quantus Fluorimeter measuring method were seen.

34

The optical density ratios of the wavelengths 260 nm and 280 nm after the NucleoSpin

approach outpace the 1.8 ratio limit for all the samples. The OD A260/A230 ratios were only

higher than 1.8 for the seeds of Bell Pepper AURELIO and Peperone Yucatan. Generally,

differences between spectrophotometric and fluorimetric DNA concentrations are less

expressed for the SEEDS samples. It is known that the Biospec Nano spectrophotometer

measures all DNA, including ssDNA present in a sample, while Quantus measures only the

intact dsDNA. Seeds give more or less pure dsDNA and no ssDNA or degraded DNA nor RNA.

For the FLESH samples, the NucleoSpin Food Kit granted us more DNA than the Qiagen

method (Table 4.1.3A). The 400 ppm peanut in pepper samples and negative controls also

underwent the two extraction methods (Table 4.1.3B). All though, very low DNA

concentrations were obtained from the mesocarp samples. The maximum DNA

concentration, 19.07 ng/µL, was measured from the SPANISH Pepper after the Qiagen

extraction. Bell Pepper AURELIO gave the highest DNA concentration after the NucleoSpin

extraction, namely 46.61 ng/µL. There were no noteworthy differences between the

spectrophotometric and fluorimetric method after the Qiagen Dneasy Plant Mini Kit. After

the NucleoSpin extraction some samples showed a decreased DNA concentration of ¼ when

measured with the Quantus Fluorimeter. For other samples Quantus measured about the

half of what Biospec Nano measures. The OD A260/A280 ratios varied after the Qiagen DNA

extraction around the 1.8 limit. The OD A260/A230 ratios for the mesocarp extracts were very

low, so that information about contaminants could not be well defined after the NucleoSpin

method.

Also two SEEDS+FLESH samples, Peperone CANCUN and Peperone SALTILLO, were

examined. The DNA extraction took place after the homogenization of the seeds and

mesocarp as one to evaluate DNA concentrations from seed-mesocarp complex (Table 4.1.4).

Again, the NucleoSpin method gives higher DNA yields than Qiagen. Major differences

between the two DNA measuring methods are also obvious. The DNA concentrations are up

to 2 or 3 times higher with the Biospec Nano spectrophotometer.

35

Overall, the OD A260/A280 ratios of the two samples were higher than 1.8 for but under

the ratio of 2.0. Looking at the OD A260/A230 ratio, Qiagen extraction gives too low OD ratios

(<1.0). With the NucleoSpin values of more than 1.8, the standard limit, were achieved.

The positive controls, two different types of pure peanuts, underwent only one DNA

extraction method, the Qiagen method (Table 4.1.5). Salted peanuts and roasted peanuts

gave concentrations around 18 ng/µL with Biospec Nano. The Quantus Fluorimeter measures

5 times lower DNA concentrations for the six samples. As listed, for the purity of the DNA,

the samples show higher OD A260/A280 ratios than 1.8. For roasted peanuts, all three extracts

have a lower OD A260/A230 ratios below 1.8. For salted peanuts, only one extract of the three

had an OD A260/A230 ratio higher than 1.8. The two other extracts have values close to the 1.8

limit ratio.

4.1.2 PCR detection of peanut in pepper

Real-time PCR results can show if there is any cross-reactivity at DNA level for peanut

with the bell peppers/chili peppers on DNA level. Peanut in pepper positive control samples

showed all positive signals for the peanut specific Ara h3 sequence. The 0 ppm sample, where

no peanut was processed in, also showed a similar signal to the samples in which peanut was

clearly processed. Table 4.1.6 shows the obtained Cp values. For the negative controls, ultra-

pure water extract, no signal was detected. The pure peanut controls (C+1 & C+1’) show

clearly positive signals around Cp of 22. For the SEEDS, FLESH and SEEDS+FLESH samples, the

results, including the results of the positive controls, are listed in Table 4.1.7A and Table

4.1.7B

No positive signal was detected for the samples of the eleven varieties of bell pepper

and chili pepper. The positive controls, 400 ppm peanut in pepper extracts and the dilution

of 40 ng/µL showed Cp around 38. The pure peanut samples, roasted and salted peanuts,

showed Cp around 25.

36

4.1.3 ELISA detection of peanut in pepper

With an ELISA method another molecular level, namely the protein level, of the

samples was investigated. A commercial kit, Ridascreen FAST Peanut was used to determine

the protein concentration, in parts per million, of the samples. First, peanut in pepper dilution

series were examined. The 50, 100, 400 ppm and the pure peanut samples were diluted to

20 ppm. Table 4.1.8 shows the concentrations calculated, taking the dilution factor into

account. All the samples showed a signal for peanut. The 0 ppm peanut in pepper sample

showed as for the real-time result also a signal for peanut. The calculated concentrations

surpass the theoretically spiked concentrations. Only the 50 ppm sample had a ppm value of

44.58 which was in correspondence with the theoretically spiked concentration.

The SEEDS and SEEDS+FLESH samples were put together with the 1, 5, 20, 50 and 100

ppm peanut in pepper samples in one ELISA test to determine if there was any cross-reactivity

with peanut (Table 4.1.9). The SEEDS and SEEDS+FLESH samples tested negative, described

as a concentration lower than the LOQ of 2.5 ppm. For the two SEEDS protein extracts from

JALAPENA equal results were obtained. For the positive controls, the peanut in pepper

samples, the same concentration was calculated for different spiking concentrations. An

absorbance measurement was also performed 5 minutes after adding the stop solution. A

light increase in absorbance was observed for the peanut in pepper samples, resulting in an

increase of concentration from 16.89 ppm to 17.02 ppm.

Negative results, namely concentrations under 2.5 ppm, were also relevant for the

FLESH samples (Table 4.1.10). The 1, 5, 20 and 50 ppm peanut in pepper samples were also

set up in the same ELISA test. Again the same peanut concentration was calculated for the

positive controls i.e. 14.99 ppm. Now, a light decrease in absorbance was observed for these

samples 5 minutes after adding the stop solution. The concentration was lowered to 14.8

ppm for the peanut in pepper samples.

37

4.1.4 ELISA detection of peanut in rice

The odd results of the peanut in pepper requested an extra control ELISA test. Rice

spiked with peanut was used in this test. Following concentrations were examined undiluted

with Ridascreen FAST Peanut: 0, 0.5, 2, 5, 50, 100, 400 and 4000 ppm (Table 4.1.11). For the

0 ppm sample no peanut protein was detected. The 0.5 ppm sample had a peanut

concentration of 1.53 ppm with the ELISA method. The 2 and 5 ppm samples had peanut

concentrations of respectively 5.01 ppm and 9.89 ppm. The 50 ppm sample had a calculated

concentration of 137.48 ppm and a concentration of 164.64 ppm 5 minutes after adding the

stop solution. The remaining samples, 100, 400 and 4000 ppm, give peanut concentrations

of 140.07 ppm, 127.43 ppm and 156.25 ppm respectively and measured immediately after

adding the stop solution. An increase in the concentration was observed after 5 minutes,

resulting in the following concentrations 182.51 ppm, 143.73 ppm and 182.51 ppm.


4.2.1 DNA concentration measurement and qPCR inhibition test

The DNA extractions of the flour matrices and of some pure nuts (pecan, hazelnut,

peanut, walnut and pistachio) obtained with the commercial SureFood Prep Advanced kit,

underwent an extra DNA purifying step with the PCR clean-up NucleoSpin kit. The DNA

concentrations, the OD A260/A280 ratios and the OD A260/A230 ratios, measured with the

Biospec Nano spectrophotometer, are illustrated in Table 4.2.1. The DNA concentrations of

the spiked flour matrices were all above 100 ng/µL after the PCR clean-up. Fluctuating OD

A260/A280 ratios around 1.9 were measured for these samples. OD A260/A230ratios of the flour

matrices were all above 1.8, only the 25 ppm A sample had a ratio of 1.68.

DNA concentrations of the pure nuts samples above 4 ng/µL were defined as suitable

concentrations for the next step, the real-time PCR. After the DNA extraction a test PCR was

set up for the pecan detection. Herewith, the 100 ppm A flour matrix sample was diluted with

ultra-pure water to concentrations varying from 0.976463 ng/µL to 500 ng/µL. After the real-

time PCR, no inhibition effects could be detected.

38

Pecan was detected in some dilution samples. The lowest DNA concentration with

detectable pecan was 62.5 ng/µL. In one of the 125 ng/µL and one of the 500 ng/µL samples

pecan was also detected. Both 250 ng/µL samples showed presence of pecan DNA sequences.

After this test, no inhibition was occurred with high, up to 500 ng/µL, DNA concentrations.

4.2.2 qPCR detection of pecan in flour

Now, the flour matrices and pure nuts were put undiluted (concentrations as high as

possible) in the Lightcycler 480II after adding the master mix and inhibition control mix to the

samples (SureFood ALLERGEN ID Pecan kit). The Cp values listed in Table 4.2.2, whereby the

difference between the Cp values of the positive controls and the samples was more than 2

units, illustrate possible inhibition substances have interfered.

4.2.3 ELISA detection of peanut and hazelnut in flour

The flour matrices spiked with 9 different nuts were tested with peanut and hazelnut

ELISA. Peanut ELISA set ups are mentioned in Table 4.2.3. Pure peanut samples, which are

diluted from a 100 % pure peanut sample, give corresponding protein concentrations. Only

the 1 ppm pure peanut sample had a protein concentration under the LOQ of 1 ppm as shown

in Table 4.2.4. Pure peanut in flour was examined to study the effect of the flour on the

detectability of peanut. Different dilution samples were provided: 2, 20, 50, 400 and 4000

ppm. Only the 2 ppm sample was kept unaltered. The other samples were diluted to 5 ppm

with TE buffer after the protein extraction. The calculated protein concentrations were for all

samples overestimated as shown in Table 4.2.5. The positive control, a diluted sample of pure

peanut with a concentration of 5 ppm, could not be detected. The absorbance of the sample

at 450 nm was lower than the LOD. Then an ELISA was performed as purpose to investigate

cross-reactivity between peanut and other nuts. Five of the eight nuts showed cross-

reactivity with peanut (Table 4.2.6). The pure brazil nut sample contained according to the

ELISA 15.66 ppm peanut. The almond, macadamia, cashew and pistachio samples contained

respectively 1.06, 2.13, 3.04 and 8.96 ppm peanut according to the AgraQuant Plus Peanut.

A positive control, pure peanut was diluted to 20 ppm.

39

The computed concentration was higher than 25 ppm, the upper limit of the

detectability range of the AgraQuant Plus Peanut ELISA.

The last of four ELISAs consists of the flour matrices spiked with the 9 different nuts

(Table 4.2.7). Concentrations vary from 0 ppm to 100 ppm. The samples 25, 50 and 100 ppm

were diluted to 20 ppm with TE buffer. Here, a positive control of pure peanut was also

included and diluted to 20 ppm. Only the 0 ppm sample showed a correct result. The other

samples had an overestimated calculated concentration after the ELISA test. The samples

1.5625, 3.125, 6.25 ppm had three times higher calculated concentrations with the

AgraQuant Plus Peanut than theoretically spiked.

For hazelnut the same ELISA set ups were used, with this exception that pure hazelnut

in flour was not available (Table 4.2.8). The three other ELISA’s were performed with

AgraQuant Plus Hazelnut. The detection of hazelnut is possible if the concentration of

hazelnut is higher than 1 ppm(LOD). The first ELISA aims at testing the detection limits of the

ELISA kit. Therefore, a dilution series of pure hazelnut was made. 0.5, 1, 5, 10 and 20 ppm

were tested. Only the 1 ppm sample was perfectly calculated comparing to the theoretically

diluted sample. The other samples; 0.5 ppm sample a specific concentration could not be

assigned, because of the limit of detection and the concentrations of other dilution samples

were underestimated. The calculated concentrations are listed up in Table 4.2.9.

Cross-reactivity between the other nuts was detected with AgraQuant Plus Hazelnut

in the third setup. The pure nut samples pecan, walnut, macadamia and cashew contained

more than 25 ppm according to the test. The other nuts showed also cross-reactivity with

concentrations illustrated in Table 4.2.10.

The flour matrices with the 9 different nuts, the fourth and last setup, were tested too.

The results are shown in Table 4.2.11. The calculated protein concentrations for hazelnut are

comparable with the theoretical spiked values. Only for the pure hazelnut which was diluted

to 20 ppm almost a 7 times underestimation of the concentration was calculated, resulting

in a hazelnut concentration of 3.01 ppm.

40

5 DISCUSSION


For the pepper seeds tested in this part of the study, no remarkable differences are

noticed between the applied DNA extraction techniques, nor between the DNA

measurement techniques. Still, the highest DNA concentrations are obtained with the

NucleoSpin extraction method. The OD A260/A280 and OD A260/A230 ratios, measured with the

BioSpec-nano spectrophotometer for the Qiagen and NucleoSpin extracts, were as well

comparable. The reason is probably that seeds form quite a pure, simple matrix in which the

DNA is well stored and conserved. This is reflected in the highest DNA concentrations, which

are obtained from the bell pepper and chili pepper seeds (in relation to the flesh or the whole

intact pepper fruit).

The flesh and seeds+flesh (thus intact) samples had lower DNA concentrations

compared to the seeds. The difference between freshly cool-stored flesh samples and whole

fruits dried at room temperature was not remarkable. Looking at the seed samples,

suggesting the seeds+flesh (whole fruit) samples would give rise to high DNA concentrations

was not odd to expect. However, in practice, the seeds+flesh samples gave DNA

concentrations around 20 ng/µL. The influence of the mesocarp of the peppers can be the

cause of this matter. Flesh of plants is very sensitive to little changes of the environment.

Looking at pure peanut samples, both DNA extraction methods yield much lower DNA

concentrations. Fat, which is abundant in nuts, can obstruct the DNA extraction of peanut.

Looking at the peanut in pepper dilution samples, high DNA concentrations are obtained from

the NucleoSpin Food kit method. It has to be mentioned that DNA of these samples was

eluted in a smaller volume than described in the protocol of the kit. Also, low OD A260/A230

ratios were obtained for the peanut in pepper samples. This probably suggest that phenol

from the pepper and/or residual guanidine used in the kits were carried over into the DNA

solution.

41

Negative results for the pepper cultivars in the peanut qPCR were obtained. The qPCR

results of the 400 ppm peanut in pepper samples (undiluted and diluted), which were tested

with the seed samples, gave higher Cp values for the diluted samples. The Cp values are

inversely correlated with the DNA concentration. For the peanut in pepper dilution series,

the 0 ppm sample showed a positive signal for peanut, indicating potential contamination

with peanut. The 0 ppm sample was stored with high dilution series of peanut in pepper, up

to 40 000 ppm which can facilitate the contamination. Alternatively however, this can

indicate a true contamination of the chilipepper powder – which was used to make the ppm

series of peanut in – from the start of these experiments thus upon receipt. The qPCR test

results for the different pepper cultivars demonstrate that there is nothing in the pepper that

reacts with the tested qPCR.

No positive signals for peanut were observed for the pepper cultivars neither with the

Ridascreen FAST Peanut ELISA kit. For JALAPENA, comparison between sample preparation

with 200 mg versus 1 g was possible. Equal absorbances were achieved for both extracts,

indicating less material can be used if correct modifications are made.

Surprisingly, one constant peanut concentration was always measured in the ELISA

for the peanut in pepper dilution series, irrespective of the concentration. The formation of

a complex of two proteins present in the chilipepper and which can bind with the antibodies

in the well, can be a potential explanation for these results. Two additional ELISA tests were

performed to test this hypothesis. An ELISA test with unroasted peanut in rice was

implemented. The results show no correct concentrations for the theoretically spiked dilution

series but an increase in absorbance in line with the increasing peanut-in-rice concentrations

was observed. The second ELISA tests the peanut in pepper dilution series separately. No

equal concentrations were observed for the dilution series, but the 0 ppm sample showed a

positive signal for peanut as seen before with the qPCR test. Remarkable is that if the

calculated concentration for the 0 ppm sample is considered as a background signal, the 0.5,

1 and 5 ppm peanut in pepper samples are well calculated. This can confirm the first

hypothesis that the 0 ppm sample is contaminated.

42


The AgraQuant PLUS Peanut results of the dilution series of pure peanut with TE buffer

are comparable with the theoretical concentration values. For the pure peanut in flour

dilution series high protein concentrations were observed, indicating wheat flour enhances

the detection of peanut. Cross-reactivity with few other nuts was also observed with the

AgraQuant PLUS Peanut. Although low concentrations were measured for the other

undiluted tree nuts, positive signals have to be considered. The results of the nut-in-flour

matrices tested with AgraQuant PLUS Peanut seem to be overestimated. This can be

explained by the previous test on the sensitivity, whereby flour intensified the peanut signal.

Tree nuts will probably not have affected the sensitivity or specificity, because only very low

concentrations of the tree nuts were spiked in the flour.

Underestimated concentrations of the dilution series of pure hazelnut with TE buffer

were measured with the AgraQuant PLUS Hazelnut, indicating a false prescribed sensitivity

can be the reason for this. The ELISA test kit detected also positive signals for all other nuts.

For some nuts a concentration higher than 25 ppm was detected, but a specific concentration

could not be assigned. This illustrates that the AgraQuant PLUS Hazelnut is not hazelnut-

specific. The results of the nuts-in-flour matrices were comparable with the theoretical spiked

concentrations. This suggest that other nuts and probably flour too enhance the hazelnut

detection.

43

6 CONCLUSION

The DNA extraction methods Qiagen DNeasy Plant Mini kit and NucleoSpin Food kit

gave different DNA yields. The highest DNA yields for the pure pepper cultivars and peanut-

in-pepper dilution series were obtained with the NucleoSpin Food kit. It is expected that other

food products will gave the same results, namely higher DNA yields with the NucleoSpin Food

kit. This is based on the fact that pepper matrices already are very complex to analyse.

The Biospec Nano spectrophotometer measures high DNA concentrations in

comparison with the Quantus Fluorimeter. The spectrophotometer Biospec Nano measures

all types of DNA, including single stranded DNA, degraded DNA, less pure double stranded

DNA. Accordingly, Biospec Nano will measure high DNA concentration. The Quantus on the

other hand only measures intact double stranded DNA. Therefore, Quantus is a more reliable

DNA concentration measuring technique. But the Biospec Nano can give more information

about the purity and contamination grade of DNA solutions. The aspect on which you want

to focus will play a role in choosing between these two techniques.

Regarding the pepper cultivars, these tested all negative for peanut with the real-time

PCR, as well as with the Ridascreen FAST Peanut ELISA. Thus, no peanut presence or cross-

reactivity was observed with the pure pepper cultivars. For the peanut in pepper dilution

series, the chili pepper powder without peanut (0 ppm thus pure matrix powder) tested

positive for peanut in real-time PCR, as well as with the Ridascreen FAST Peanut, indicating

contamination of the chili pepper powder can have taken place.

44

The prescribed sensitivity of AgraQuant ELISA PLUS Hazelnut does not match the

underestimated results of the ELISA test performed with pure hazelnut dilution series. For

AgraQuant ELISA PLUS Peanut, the protein concentration of nearly all extracts was measured

correct. The ELISA kits also revealed that flour and other nuts can influence the detection of

peanut and hazelnut. For peanut, higher concentrations were measured in presence of flour

(and other tree nuts). For hazelnut correct protein concentrations were obtained. However,

lowspecificity of the AgraQuant PLUS Hazelnut makes detection of other nuts possible. The

flour can also have an effect on the detectability of Hazelnut, but there is no sureness about

this hypothesis.

In the future, the described matrices should be tested also with chemical analysis such

as LC-MS/MS. Such LC-MS/MS analysis can confirm the negative results from the pepper

cultivars with qPCR and ELISA. The peanut in pepper dilution series could be evaluated with

LC-MS/MS to give more certainty about possible contamination of the chili powder matrix.

Other AgraQuant ELISA test kits should be tested on their sensitivity and specificity before

general conclusions on the influence of wheat flour on the detectability of different nuts on

the one hand, and on the sensitivity and specificity of ELISA kits in general on the other hand,

could be made. Later, the flour matrices could also be tested with PCR-based methods with

the aim to determine the sensitivity and specificity of these methods in presence of other

substances which might influence the detectability. Last but certainly not least, it has to be

mentioned that as long as no treatments are available to cure food allergies, optimization

and development of new detection techniques remain necessary. Comparison between

different types of analyses, typically PCR versus ELISA versus peptide analysis through mass

spectrometry (e.g. HRMS) is of utmost importance, whereby the three technologies are

complementary to each other. The choice for one or another technique has to take into

account several factors such as e.g. the particular problem or question asked by the client,

the degree of processing and/or mixing the food product has undergone, but also the

availability of positive control materials and reference materials.

45

7 ANNEX

Table 4.1.2A Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of the SEEDS samples after Qiagen and

Nucleospin

DNA Extraction(SEEDS)

Qiagen(100mg)

Nucleospin(200mg)

Weight(mg) Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL) Weight(mg) Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL)

SEED 1 measured twice 102 113,07 111,85 1,86 1,84 1,86 1,84

90 200 103,93 101,92 1,78 1,76 1,65 1,71

106


71 198 155,85 154,44 1,93 1,92 2,01 2,02

131


33 / / / / /


63 198 141,68 140,22 1,81 1,77 1,34 1,37

127


127 202 113,65 114,27 1,87 1,86 2,09 2,05

101


57 202 94,38 93,76 1,81 1,84 1,34 1,38

82


44 200 107,00 106,73 1,85 1,85 1,61 1,62

82


69 198 129,92 128,80 1,88 1,85 1,76 1,78

118


79 201 147,15 147,40 1,84 1,83 1,70 1,71

154

46

Table 4.1.2B Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of the neg. controls after Qiagen and

Nucleospin

DNA Extraction(SEEDS)

Qiagen(100mg)

Nucleospin(200mg)

Weight(mg) Biospec-

NANO(ng/µL) OD

260/280 OD

260/230 Quantus(ng/µL) Weight(mg)

Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL)

H2O A 100 0,58 1,62 2,55 0,013 200 4,54 2,25 -0,67 < BLANK

H2O B 100 1,52 1,36 1,28 0,0106 200 4,14 1,67 -0,53 < BLANK

STD-LAMBDA(QUANTUS, 400 ng/µl)

399 400

47

Table 4.1.3A Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of the FLESH samples after Qiagen and

Nucleospin

DNA Extraction(FLESH)

Qiagen(100mg) Nucleospin(200mg)

Weight(mg) Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL) Weight(mg) Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL)

FLESH 1 A and B 98 101 17,35 13,22

1,77 1,72

1,5 1,61

17 14 199 199 35,01 35,28 1,93 2,01 3,92 4,87

28 22

FLESH 2 A and B 105 107 10,32 10,05

1,71 1,78

1,57 1,27

10 8,3 207 210 46,61 43,71 1,98 1,98 5,25 3,81

28 22

FLESH 3 A and B 103 106 9,41 13,78 1,87 1,88

2,11 2,24

9,7 15 197 203 36,47 43,66 2,06 2,03 16,82 8,73

21 20

FLESH 4 measured twice

96 8,38 7,98 1,95 1,90

1,08 1,11

6,4 196 15,67 16,85 1,82 1,94 -2,64 -3,90

14


107 PEAL! 10,4 11,26 1,72 1,78

1,54 1,37

9,3 197 PEAL! 34,75 34,98 1,89 1,87 5,62 5,31

28

FLESH 6 A and B 101 101 5,12 5,33 1,66 1,46

2,57 1,17

5,2 4,27 198 196 27,71 24,71 2,16 2,07 78,80 95,85

11 9

FLESH 7 A and B 105 102 4,72 5,09 1,89 1,79

1,72 1,52

4,64 4,55 195 201 17,28 16,37 1,93 2,06 -4,07 -2.90

8 8


107 PEAL! 4,22 4,24 1,68 1,81

0,76 0,76

3,18 195 PEAL! 24,47 24,67 1,95 1,92 -28,05 -47,14

18


102 PEAL! 19,02 19,07 1,92 1,87

1,74 1,78

18 207 PEAL! 31,31 31,59 1,79 1,89 226,41 21,41

25

48

Table 4.1.3B Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of the 400 ppm peanut in pepper samples

and negative controls after Qiagen and Nucleospin

DNA Extraction(FLESH)

Qiagen(100mg) Nucleospin(200mg)

Weight(mg) Biospec-

NANO(ng/µL) OD

260/280 OD

260/230 Quantus(ng/µL) Weight(mg)

Biospec-NANO(ng/µL)

OD 260/280

OD 260/230

Quantus(ng/µL)

400 PPM measured twice

100 68,18 69,72 1,80 1,83 1,19 1,17

80 200 139,73 140,83

1,89 1,90 1,64 1,61

130

400 PPM measured twice

100 45,48 45,76 1,77 1,82 1,04 1,04

37 200 72,44 72,91 1,92 1,88 1,57 1,56

52

H2O A 100 2,28 2,53 1,03 0,0106 2,94 1,59 -0,295 0,0136

H2O B 100 2,12 2,46 0,49 < BLANK 1,7 1,61 -0.18 0,0547

STD-LAMBDA(QUANTUS, 400ng/µl)

398 400

400 400

49

Table 4.1.4 Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of SEEDS+FLESH samples, 400 ppm peanut in

pepper samples and neg. controls after Qiagen and Nucleospin

DNA Extraction(SEEDS+FLESH)

Qiagen(100mg) Nucleospin(200mg) Weight

(mg) Biospec-

NANO(ng/µL) OD

260/280 OD

260/230 Quantus(ng/µL) Weight

(mg) Biospec-

NANO(ng/µL) OD

260/280 OD

260/230 Quantus(ng/µL)

SEEDS+FLESH 10 A and B 100 98

20,33 21,47 1,77 1,88

0,71 0,80

6,5 6 201 200

62,53 71,41

1,88 1,91

2,46 2,33

36 42

SEEDS+FLESH 11 A and B 101 101

18,10 22,63 1,99 1,85

0,89 0,94

6,9 8,1 201 201

86,29 85,38

1,89 1,89

1,99 1,83

64 47

400 PPM A 102 36,33 1,97 0,98 11

400 PPM B 202 96,51 1,91 1,42 85

H2O A 100 1,41 2,2 0,47 < BLANK

H2O B 200 3,06 1,73 -0,33 0,0033

STD-LAMBDA(QUANTUS, 400ng/µl)

399

400

50

Table 4.1.5 Bell peppers and chili peppers: DNA concentrations, OD A260/A280 and OD A260/A230 of the pure peanut samples after Qiagen

DNA Extraction(POS. CONTROLS) Qiagen(100mg) Weight(mg) Biospec-

NANO(ng/µL) OD 260/280 OD 260/230 Quantus(ng/µL)

C+1 99 18,35 1,96 1,56 2,99

C+1' 100 18,57 1,98 1,42 2,72

C+1" 101 16,8 1,87 1,72 2,55

C+2 102 19,13 2,06 1,64 3,23

C+2' 99 16,86 2,04 1,87 3,25

C+2" 99 17,7 2,04 1,70 3

H2O A 100 2,1 1,92 1,31 0,006

H2O B 100 2,43 2,77 0,95 0,0301

STD-LAMBDA(QUANTUS, 400ng/µl) 399

51

Table 4.1.6 Bell peppers and chili peppers: qPCR of peanut in pepper samples, pos. controls (C+1 and C+1’) and neg. controls

QPCR(Peanut in Pepper): Cp after Nucleospin NTC NEG.

NTC NEG.

H2O A NEG.

H2O B NEG.

0 PPM A and B 36,85 38,59

0,5 PPM A and B 39,65 37,98

1 PPM A and B 35,82 37,64

5 PPM A and B 37,84 38,22

20 PPM A and B 36,84 37,77

50 PPM A and B 41,01 36,86

100 PPM A and B 35,68 37,59

400 PPM A and B 36,23 35,49

C+1 22,49

C+1' 22,63

52

Table 4.1.7A Bell peppers and chili peppers qPCR of SEEDS, FLESH, SEEDS+FLESH, 400 ppm peanut in pepper, pos. controls (C+1, C+1’, C+1’’

and C+2, C+2’, C+2’’) and neg. controls

QPCR(SEEDS, FLESH, SEEDS+FLESH): Cp after Qiagen after Nucleospin NTC NEG. NEG.

NTC NEG. NEG.

H2O A NEG. NEG.

H2O B NEG. NEG.

SEED 1 diluted (40ng/µL) FLESH 1 NEG. NEG. NEG. NEG.


SEED 3 FLESH 3 NEG. NEG. / NEG.




SEED 7* FLESH 7 NEG. NEG. NEG. NEG.



SEEDS+FLESH 10 A and B NEG. NEG. NEG. NEG.

SEEDS+FLESH 11 A and B NEG. NEG. NEG. NEG.

400 PPM diluted (40ng/µL) 39,32

400 PPM diluted (40ng/µL) 37,9

400 PPM A 38,59(S+F) 36,67(S) 38,50(F)

400 PPM B 36,93(S) 38,19(F) 37,52(S+F)

53

Table 4.1.7B Bell peppers and chili peppers qPCR of SEEDS, FLESH, SEEDS+FLESH, 400 ppm peanut in pepper, pos. controls (C+1, C+1’, C+1’’

and C+2, C+2’, C+2’’) and neg. controls

QPCR(SEEDS, FLESH, SEEDS+FLESH): Cp after Qiagen

C+1 25,11(S) 25,25(F) 25,44(S+F)

C+1' 25,34(S) 25,49(F) 25,55(S+F)

C+1" 25,31(S) 25,54(F) 25,58(S+F)

C+2 24,16(S) 24,45(F) 24,45(S+F)

C+2' 24,25(S) 24,45(F) 24,48(S+F)

C+2" 24,26(S) 24,36(F) 24,50(S+F)

Remarks

*SEED 7 Nucleospin extract was also diluted (40 ng/µl)

S=SEEDS, F=FLESH and S+F=SEEDS+FLESH

54

Table 4.1.8 ELISA: Ridascreen FAST Peanut: peanut in pepper samples and pos. control (C+1)

ELISA(Peanut in Pepper) Weight(mg) Supernatant/solution (µL) RESULT* (Absorbance)

RESULT (PPM)

H20 1000 100 0,0009 < 2,5

0 PPM included in the kit stocksolution 100 0,003 0

2,5 PPM included in the kit stocksolution 100 0,492 2,5




0 PPM 1001 100 1,809 9,97

0,5 PPM 1000 100 1,852 10,42

1 PPM 998 100 2,024 12,54

5 PPM 1002 100 2,172 14,9

20 PPM 999 100 3,378 99,28

50 PPM** 999 100 2,316 44,58

100 PPM** 1000 100 3,404 524,55

400 PPM** 1000 100 3,219 1444,88

C+1** 1002 100 1,006 231365,84

*Absorbance measured quick after adding stop solution

** Samples are diluted to 20 ppm

Remarks Result* is the optical density of the diluted samples Result(ppm) is the estimated concentration after the dilution factor is been considered

55

Table 4.1.9 ELISA: Ridascreen Fast Peanut: SEEDS, SEEDS+FLESH and 1-100 ppm peanut in pepper samples

ELISA(SEEDS) Weight(mg) Supernatant/solution (µL)

RESULT* (Absorbance)

RESULT** (Absorbance)

RESULT* (PPM)

RESULT** (PPM)

H20 1000 100 -0,023 -0,024 < 2,5 < 2,5

0 PPM included in the kit stock solution 100 -0,004 -0,004 0 0

2,5 PPM included in the kit stock solution 100 0,612 0,622 2,5 2,5

5 PPM included in the kit stock solution 100 1,134 1,154 5 5



SEED 1 202 100 -0,028 -0,028 < 2,5 < 2,5

SEED 2 198 100 -0,010 0,005 < 2,5 < 2,5

SEED 3 / / / / / /

SEED 4 198 100 -0,019 -0,016 < 2,5 < 2,5

SEED 5 202 100 -0,026 -0,02 < 2,5 < 2,5

SEED 6 202 100 -0,005 -0,015 0,643 0,629

SEED 7 200 998 100 -0,016 -0,016 -0,014 -0,014 < 2,5 <2,5 < 2,5

SEED 8 198 100 0,0009 -0,004 0,635 < 2,5

SEED 9 201 100 -0,008 -0,005 < 2,5 < 2,5

SEEDS+FLESH 10 1002 100 0,17 0,181 1,03 1,04

SEEDS+FLESH 11 998 100 0,103 0,119 0,863 0,885

1 PPM 1001 100 2,8 2,816 16,89 17,02

5 PPM 1002 100 2,8 2,816 16,89 17,02

20 PPM 1004 100 2,8 2,816 16,89 17,02

50 PPM 1005 100 2,8 2,816 16,89 17,02

100 PPM 1003 100 2,8 2,816 16,89 17,02

*Absorbance measured/estimated concentration quick after adding stop solution

**Absorbance measured/estimated concentration 5min. after adding stop solution

56

Table 4.1.10 ELISA: Ridascreen FAST Peanut: FLESH and 1-50 ppm peanut in pepper samples

ELISA(FLESH) Weight(mg) Supernatant/solution (µL)

RESULT* (Absorbance)


RESULT* (PPM)

RESULT** (PPM)

H20 1000 100 -0,015 -0,025 < 2,5 < 2,5

0 PPM included in the kit stocksolution 100 0,002 0,0004 0 0

2,5 PPM included in the kit stocksolution 100 0,678 0,689 2,5 2,5




FLESH 1 1001 1011 100 -0,005 -0,005 0,0003 0,0003 < 2,5 < 2,5 < 2,5 < 2,5

FLESH 2 1003 1001 100 -0,017 -0,017 -0,017 -0,017 < 2,5 < 2,5 < 2,5 < 2,5

FLESH 3 997 993 100 -0,016 -0,016 -0,014 -0,014 < 2,5 < 2,5 < 2,5 < 2,5

FLESH 4 208 100 0,008 -0,011 0,194 0,206

FLESH 5 / / / / / /

FLESH 6 998 995 100 -0,011 -0,011 -0,010 -0,010 < 2,5 < 2,5 < 2,5 < 2,5

FLESH 7 995 996 100 -0,008 -0,008 -0,007 -0,007 < 2,5 < 2,5 < 2,5 < 2,5

FLESH 8 1005 PEAL! 100 -0,016 -0,015 < 2,5 < 2,5

FLESH 9 1006 PEAL! 100 -0,013 -0,01 < 2,5 < 2,5

1 PPM 997 100 2,718 2,816 14,99 14,8

5 PPM 996 100 2,718 2,816 14,99 14,8

20 PPM 1005 100 2,718 2,816 14,99 14,8

50 PPM 999 100 2,718 2,816 14,99 14,8



57

Table 4.1.11 ELISA: Ridascreen FAST Peanut: Unroasted peanut in rice samples

ELISA(Unroasted Peanut in Rice) Weight(mg) Supernatans/solution (µL) RESULT* (Absorbance)


RESULT* (PPM)

RESULT** (PPM)

H20 1000 100 0,167 0,169 < 2,5 < 2,5

0 PPM included in the kit stocksolution 100 0,160 0,160 0,161 0,161 0 0

2,5 PPM included in the kit stocksolution 100 0,674 0,674 0,682 0,682 2,5 2,5




0 PPM A and B 999 1003 100 0,151 0,151 0,158 0,158 < 2,5 < 2,5 <2,5 <2,5

0,5 PPM A and B 1005 997 100 0,399 0,399 0,434 0,434 1,33 1,33 1,53 1,53

2 PPM A and B 1006 1000 100 1,184 1,184 1,202 1,202 5,13 5,13 5,01 5,01

5 PPM A and B 1006 1000 100 1,996 1,996 2,018 2,018 9,88 9,88 9,89 9,89

50 PPM A and B 995 995 100 3,707 3,707 3,771 3,771 137,48 137,48

164,64 164,64

100 PPM 999 100 3,715 3,812 140,07 140,07

182,51 182,51

400 PPM 1001 100 3,674 3,715 127,43 127,43

143,73 143,73

4000 PPM 998 100 3,761 3,812 156,25 156,25

182,51 182,51



58

Table 4.2.1 Wheat flour matrices: DNA concentrations, OD A260/A280 and OD A260/A230 of spiked flour matrices and pure nuts and neg.

controls after SureFood Prep Advanced (and Nucleospin PCR clean-up)

DNA extraction (Wheat flour and Pure nuts)

SureFood Prep Advanced(150mg) Weight(mg) Biospec-

NANO(ng/µL) OD

260/280 OD 260/230 (*)after PCR

clean-up(ng/µL)

OD 260/280

OD 260/230

0 PPM* A and B 153 152 112,37 74,93 2,07 2,05 1,81 2,00 186,15 111,35 1,93 1,94 2,6 2,44

1,5625 PPM* A and B 149 150 82,16 79,56 2,05 2,05 2,54 2,00 138,19 132,09 1,93 1,94 2,33 2,44

3,125 PPM* A and B 151 149 74,88 76,60 2,08 2,04 0,33 2,41 148,07 136,30 1,94 1,94 2,22 2,32

6,25 PPM* A and B 152 152 100,31 89,81 2,07 2,07 2,67 1,09 172,42 122,37 1,96 1,93 2,37 2,60

12,5 PPM* A and B 152 150 75,71 85,97 2,08 2,04 2,24 0,98 143,23 149,57 1,91 1,91 2,16 1,84

25 PPM* A and B 152 149 90,02 104,56 2,04 2,06 1,43 2,66 137,29 204,64 1,93 1,95 1,68 2,27

50 PPM* A and B 151 149 92,56 70,93 2,05 2,04 0,99 3,21 176,17 117,18 1,93 1,92 2,35 2,40

100 PPM* A and B 149 148 105,95 103,03 2,05 2,05 2,63 2,43 167,24 170,94 1,93 1,94 2,28 1,84

PECAN* A and B 152 148 1,54 1,12 2,26 1,23 0,18 -0,20 12,56 6,27 2,61 1,74 0,95 -3,02

BRAZIL NUT A and B 151 150 4,89 7,11 1,79 2,25 0,25 1,05

PEANUT A and B* 148 151 10,74 3,74 1,79 1,56 0,56 -1,64 11,52 1,88 5,06

HAZELNUT A* and B 147 148 0,7 7,07 0,69 2,36 -0,25 0,89 8,56 1,73 10,58

WALNUT* A and B 147 152 -2,04 3,14 0,26 2,1 -0,08 -0,55 9,59 13,15 1,78 1,93 1,00 0,58

MACADAMIA A and B 150 151 57,12 46,40 2,22 2,19 1,79 1,96

CASHEW A and B 153 153 26,87 27,17 2,14 2,07 1,43 3,28

ALMOND A and B 150 150 6,55 6,98 1,77 1,78 -1,61 -19,53

PISTACHIO A* and B 151 148 1,08 9,92 0,77 1,92 -2,92 1,41 6,5 1,7 0,51

H2O A 150 0,5 4,22 -0,95

H2O B 150 1,29 1,38 -0,76

59

Table 4.2.2 Wheat flour matrices: qPCR (SureFood ALLERGEN Pecan ID) of wheat flour matrices, pure nuts, pos. controls and neg. controls

QPCR(WHEAT FLOUR): Cp after SureFood Prep Advanced

NTC 36,48

NTC 38,27

H2O A 34,87

H2O B /

0 PPM A and B / 29,73

1,5625 PPM A and B 29,97 29,74

3,125 PPM A and B 29,90 29,87

6,25 PPM A and B 29,98 29,88

12,5 PPM A and B 30,03 29,70

25 PPM A and B 29,81 29,97

50 PPM A and B 30,09 29,70

100 PPM A and B 29,93 29,89

PECAN A and B 29,60 29,50

BRAZIL NUT A and B 30,08 30,08

PEANUT A and B 30,23 29,49

HAZELNUT A and B 29,64 30,20

WALNUT A and B 29,36 29,61

MACADAMIA A and B 30,31 30,18

CASHEW A and B 30,29 30,37

ALMOND A and B 30,19 30,24

PISTACHIO A and B 29,59 30,21

POS. CONTROL included in kit A and B / 37,37

60

Table 4.2.3 Wheat flour matrices: ELISA: AgraQuant PLUS Peanut: set ups

-columns 1-3: ELISA set up for the dilution series of pure peanut (0.5-20ppm), including standards of the AgraQuant PLUS Peanut kit and negative controls: NTC buffer and water extraction. -columns 4-6: ELISA set up for the dilution series of pure peanut in wheat flour (2-4000ppm), including standards of the AgraQuant PLUS Peanut kit, negative controls: NTC buffer and water extract, positive control of pure peanut (5 ppm). * diluted to 5 ppm with TE buffer -columns 7-9: ELISA set up for the undiluted tree nuts (1 000 000 ppm): pecan nut, brazil nut, hazelnut, walnut, macadamia nut, cashew, almond, pistachio. Included in the set up are standards of the AgraQuant PLUS Peanut kit, negative controls: NTC buffer and water extract, positive control of pure peanut (20 ppm). ** diluted to 20 ppm with TE buffer -columns 10-12: ELISA set up for the dilution series of the 9 different nuts in wheat flour (0-100 ppm), including the standards of the AgraQuant PLUS Peanut kit, negative controls: NTC buffer and water extract, positive control of pure peanut (20 ppm). ** diluted to 20 ppm with TE buffer.

1 2 3 4 5 6 7 8 9 10 11 12

A NTC STD 3 1 PPM A NTC STD4 50 PPM A* NTC PECAN B MAC B NTC 0 PPM B 12,5 PPM B

B NTC STD 3 1 PPM B H2O STD4 50 PPM B* H2O BRAZILNUT A CASH A H2O 1,5625 PPM

A 25 PPM A**

C H2O STD 4 5 PPM A STD1 STD5 400 PPM A* STD1 BRAZILNUT B CASH B STD1 1,5625 PPM

B 25 PPM B**

D H20 STD4 5 PPM B STD1 STD5 400 PPM B* STD2 HAZELNUT A ALMOND A STD2 3,125 PPM A 50 PPM A**

E STD 1 STD 5 10 PPM A STD2 2 PPM A 4000 PPM

A* STD3 HAZELNUT B ALMOND B STD3 3,125 PPM B 50 PPM B**

F STD 1 STD 5 10 PPM B STD2 2 PPM B 4000 PPM

B* STD4 WALNUT A PISTACHIO A STD4 6,25 PPM A

100 PPM A**

G STD 2 0,5 PPM A 20 PPM A STD3 20 PPM A* PEANUT A* STD5 WALNUT B PISTACHIO B STD5 6,25 PPM B 100 PPM

B**

H STD 2 0,5 PPM A 20 PPM B STD3 20 PPM B* PEANUT B* PECAN A MAC A PEANUT A** 0 PPM A 12,5 PPM A PEANUT B**

61

Table 4.2.4 Wheat flour matrices: ELISA: AgraQuant PLUS Peanut: pure peanut diluted

ELISA(PURE PEANUT diluted) Weight(mg) Supernatant/solution (µL) RESULT*

(Absorbance) RESULT (PPM)

0 PPM included in the kit stock solution 100 -0,132 0


5 PPM included in the kit stock solution 100 0,334 5



0,5 PPM A and B ** 100 -0,009 1,18

1 PPM A and B ** 100 -0,089 <LOD

5 PPM A and B ** 100 0,417 6,12

10 PPM A and B ** 100 0,721 10,36

20 PPM A and B ** 100 1,169 20,99

*Absorbance measured/estimated concentration quick after adding stop solution ** Dilution made from 1 peanut extract(1010mg)

62

Table 4.2.5 Wheat flour matrices: ELISA: AgraQuant PLUS Peanut: pure peanut in wheat flour

ELISA(PURE PEANUT in wheat flour) Weight(mg) Supernatant/solution (µL) RESULT** (Absorbance)

RESULT (PPM)






2 PPM A and B 1001 100 0,99 12,44

20 PPM* A and B 1000 100 1,545 >25 PPM***

50 PPM* A and B 998 100 1,448 >25 PPM***

400 PPM* A and B 1002 100 1,331 22,71***

4000 PPM* A and B 1000 100 1,034 13,77***

PEANUT* 1010 100 0,046 <LOD***

*Diluted to 5 PPM

**Absorbance measured/estimated concentration quick after adding stop solution

*** Result (PPM) of the diluted samples

63

Table 4.2.6 Wheat flour matrices: ELISA: AgraQuant PLUS Peanut: undiluted nuts

ELISA(NUTS) Weight(mg) Supernatant/solution (µL) RESULT** (Absorbance)

RESULT (PPM)






PECAN A and B 1011 100 0,055 <LOD

BRAZIL NUT A and B 990 100 1,08 15,66

HAZELNUT A and B 1000 100 0,049 <LOD

WALNUT A and B 990 100 -0,0006 <LOD

MACADAMIA NUT A and B 1006 100 0,217 2,13

CASHEW A and B 1008 100 0,323 3,04

ALMOND A and B 1006 100 0,093 1,06

PISTACHIO A and B 1000 100 0,805 8,96

PEANUT* A and B 1010 100 1,442 >25 PPM

*Diluted to 20 PPM


64

Table 4.2.7 Wheat flour matrices: ELISA: AgraQuant PLUS Peanut: wheat flour spiked with 9 different nuts

ELISA(Flour spiked with 9 different nuts)

Weight(mg) Supernatant/solution (µL) RESULT** (Absorbance)

RESULT (PPM)






0 PPM A and B 998 100 -0,041 <LOD

1,5625 PPM A and B 994 100 0,466 5,12

3,125 PPM A and B 1002 100 0,866 9,77

6,25 PPM A and B 1005 100 1,052 15,11

12,5 PPM NUT A and B 1007 100 1,531 >25 PPM

25 PPM* A and B 993 100 1,889 >25 PPM***

50 PPM* A and B 995 100 1,908 >25 PPM***

100 PPM* A and B 999 100 1,918 >25 PPM***

PEANUT* A and B 1010 100 1,533 >25 PPM***

*Diluted to 20 PPM


***Result (PPM) of the diluted samples

65

Table 4.2.8 Wheat flour matrices: ELISA: AgraQuant PLUS Hazelnut: set ups

1 2 3 4 5 6 7 8 9

A NTC STD 3 1 PPM A NTC PECAN B MAC B NTC 0 PPM B 12,5 PPM B

B NTC STD 3 1 PPM B H2O BRAZILNUT A CASH A H2O 1,5625 PPM A 25 PPM A**

C H2O STD 4 5 PPM A STD1 BRAZILNUT B CASH B STD1 1,5625 PPM B 25 PPM B**

D H20 STD4 5 PPM B STD2 PEANUT A ALMOND A STD2 3,125 PPM A 50 PPM A**

E STD 1 STD 5 10 PPM A STD3 PEANUT B ALMOND B STD3 3,125 PPM B 50 PPM B**

F STD 1 STD 5 10 PPM B STD4 WALNUT A PISTACHIO A STD4 6,25 PPM A 100 PPM A**

G STD 2 0,5 PPM A 20 PPM A STD5 WALNUT B PISTACHIO B STD5 6,25 PPM B 100 PPM B**

H STD 2 0,5 PPM A 20 PPM B PECAN A MAC A HAZELNUT A* 0 PPM A 12,5 PPM A HAZELNUT B**

-columns 1-3: ELISA set up for the dilution series of pure hazelnut (0.5-20ppm), including standards of the AgraQuant PLUS Hazelnut kit and negative controls: NTC buffer and water extraction. -columns 4-6: ELISA set up for the undiluted tree nuts (1 000 000 ppm): pecan nut, brazil nut, peanut, walnut, macadamia nut, cashew, almond, pistachio. Included in the set up are standards of the AgraQuant PLUS Hazelnut kit, negative controls: NTC buffer and water extract, positive control of pure hazelnut (5 ppm). * diluted to 5 ppm with TE buffer -columns 7-9: ELISA set up for the dilution series of the 9 different nuts in wheat flour (0-100 ppm), including the standards of the AgraQuant PLUS Hazelnut kit, negative controls: NTC buffer and water extract, positive control of pure hazelnut (20 ppm). ** diluted to 20 ppm with TE buffer.

66

Table 4.2.9 Wheat flour matrices: ELISA: AgraQuant PLUS Hazelnut: pure hazelnut diluted

ELISA(PURE HAZELNUT diluted) Weight(mg) Supernatant/solution (µL) RESULT*

(Absorbance) RESULT (PPM)






0,5 PPM A and B ** 100 -0,00065 <LOD

1 PPM A and B ** 100 0,006 1,00

5 PPM A and B ** 100 0,031 1,23

10 PPM A and B ** 100 0,096 1,84

20 PPM A and B ** 100 0,373 4,63

*Absorbance measured/estimated concentration quick after adding stop solution **Dilution made from 1 hazelnut extract(1004mg)

67

Table 4.2.10 Wheat flour matrices: ELISA: AgraQuant PLUS Hazelnut: undiluted nuts

ELISA(NUTS) Weight(mg) Supernatant/solution (µL) RESULT** (Absorbance)

RESULT (PPM)






PECAN A and B 1003 100 1,498 >25 PPM

BRAZIL NUT A and B 1004 100 0,649 11,40

PEANUT A and B 1007 100 0,106 1,70

WALNUT A and B 996 100 1,443 >25 PPM

MACADAMIA NUT A and B 1008 100 2,064 > 25 PPM

CASHEW A and B 1004 100 2,39 > 25 PPM

ALMOND A and B 1008 100 0,31 5,18

PISTACHIO A and B 1009 100 0,161 2,39

HAZELNUT* A and B 1004 100 0,063 1.32

*Diluted to 5 PPM


68

Table 4.2.11 Wheat flour matrices: ELISA: AgraQuant PLUS Hazelnut: wheat flour spiked with 9 different nuts

ELISA(Flour spiked with 9 different nuts)

Weight(mg) Supernatant/solution (µL) RESULT** (Absorbance)

RESULT (PPM)






0 PPM A and B 1002 100 0,12 <LOD

1,5625 PPM A and B 1005 100 0,184 2,17

3,125 PPM A and B 1004 100 0,29 3,21

6,25 PPM A and B 1001 100 0,531 5,83

12,5 PPM NUT A and B 1006 100 0,882 11,58

25 PPM* A and B 998 100 1,096 17,63***

50 PPM* A and B 997 100 1,,193 20,37***

100 PPM* A and B 998 100 1,04 16.05***

HAZELNUT* A and B 1004 100 0,27 3,01***

*Diluted to 20 PPM


***Result (PPM) of the diluted samples

69

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19. Beyer K, Morrow E, Li XM, Bardina L, Bannon GA, Burks AW, et al. Effects of cooking methods on peanut allergenicity. J Allergy Clin Immunol. 2001;107(6):1077-81. 20. Chung SY, Reed S. Removing peanut allergens by tannic acid. Food Chem. 2012;134(3):1468-73. 21. Cabanillas B, Maleki SJ, Rodriguez J, Burbano C, Muzquiz M, Jimenez MA, et al. Heat and pressure treatments effects on peanut allergenicity. Food Chem. 2012;132(1):360-6. 22. Jayasena S, Smits M, Fiechter D, de Jong A, Nordlee J, Baumert J, et al. Comparison of six commercial ELISA kits for their specificity and sensitivity in detecting different major peanut allergens. J Agric Food Chem. 2015;63(6):1849-55. 23. Peng J, Song S, Xu L, Ma W, Liu L, Kuang H, et al. Development of a monoclonal antibody-based sandwich ELISA for peanut allergen Ara h 1 in food. Int J Environ Res Public Health. 2013;10(7):2897-905. 24. The polymerase chain reaction: An overview and development of diagnostic PCR protocols at the LCDC. The Canadian journal of infectious diseases = Journal canadien des maladies infectieuses. 1991;2(2):89-91. 25. Fellahi S, Harrak ME, Kuhn JH, Sebbar G, Bouaiti EA, Khataby K, et al. Comparison of SYBR green I real-time RT-PCR with conventional agarose gel-based RT-PCR for the diagnosis of infectious bronchitis virus infection in chickens in Morocco. BMC Research Notes. 2016;9:231. 26. Garino C, De Paolis A, Coisson JD, Bianchi DM, Decastelli L, Arlorio M. Sensitive and specific detection of pine nut (Pinus spp.) by real-time PCR in complex food products. Food Chem. 2016;194:980-5. 27. Platteau C, De Loose M, De Meulenaer B, Taverniers I. Quantitative detection of hazelnut (Corylus avellana) in cookies: ELISA versus real-time PCR. J Agric Food Chem. 2011;59(21):11395-402. 28. Xiao G, Qin C, Wenju Z, Qin C. Development of a real-time quantitative PCR assay using a TaqMan minor groove binder probe for the detection of alpha-lactalbumin in food. Journal of dairy science. 2016;99(3):1716-24. 29. Sun Y, Lu X, Su F, Wang L, Liu C, Duan X, et al. Real-time fluorescence ligase chain reaction for sensitive detection of single nucleotide polymorphism based on fluorescence resonance energy transfer. Biosensors & bioelectronics. 2015;74:705-10. 30. Radstrom P, Knutsson R, Wolffs P, Lovenklev M, Lofstrom C. Pre-PCR processing: strategies to generate PCR-compatible samples. Molecular biotechnology. 2004;26(2):133-46. 31. Wiedbrauk DL, Werner JC, Drevon AM. Inhibition of PCR by aqueous and vitreous fluids. Journal of clinical microbiology. 1995;33(10):2643-6. 32. Monteiro L, Bonnemaison D, Vekris A, Petry KG, Bonnet J, Vidal R, et al. Complex polysaccharides as PCR inhibitors in feces: Helicobacter pylori model. Journal of clinical microbiology. 1997;35(4):995-8. 33. Belec L, Authier J, Eliezer-Vanerot MC, Piedouillet C, Mohamed AS, Gherardi RK. Myoglobin as a polymerase chain reaction (PCR) inhibitor: a limitation for PCR from skeletal muscle tissue avoided by the use of Thermus thermophilus polymerase. Muscle & nerve. 1998;21(8):1064-7. 34. Khan G, Kangro HO, Coates PJ, Heath RB. Inhibitory effects of urine on the polymerase chain reaction for cytomegalovirus DNA. Journal of clinical pathology. 1991;44(5):360-5.

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35. Gerdes L, Iwobi A, Busch U, Pecoraro S. Optimization of digital droplet polymerase chain reaction for quantification of genetically modified organisms. Biomolecular detection and quantification. 2016;7:9-20. 36. Felix-Urquidez D, Perez-Urquiza M, Valdez Torres JB, Leon-Felix J, Garcia-Estrada R, Acatzi-Silva A. Development, Optimization, and Evaluation of a Duplex Droplet Digital PCR Assay To Quantify the T-nos/hmg Copy Number Ratio in Genetically Modified Maize. Analytical chemistry. 2016;88(1):812-9. 37. Dreo T, Pirc M, Ramsak Z, Pavsic J, Milavec M, Zel J, et al. Optimising droplet digital PCR analysis approaches for detection and quantification of bacteria: a case study of fire blight and potato brown rot. Anal Bioanal Chem. 2014;406(26):6513-28. 38. Sealey-Voyksner J, Zweigenbaum J, Voyksner R. Discovery of highly conserved unique peanut and tree nut peptides by LC-MS/MS for multi-allergen detection. Food Chem. 2016;194:201-11. 39. Barnouin K. Two-dimensional gel electrophoresis for analysis of protein complexes. Methods in molecular biology (Clifton, NJ). 2004;261:479-98. 40. Picariello G, Mamone G, Addeo F, Ferranti P. The frontiers of mass spectrometry-based techniques in food allergenomics. J Chromatogr A. 2011;1218(42):7386-98. 41. Schubert-Ullrich P, Rudolf J, Ansari P, Galler B, Fuhrer M, Molinelli A, et al. Commercialized rapid immunoanalytical tests for determination of allergenic food proteins: an overview. Anal Bioanal Chem. 2009;395(1):69-81. 42. http://www.phadia.com/en-US/Products/Products/ImmunoCAP-ISAC/Test-Principle-ImmunoCAP-ISAC/ (29-04-2016) 43.http://www.fda.gov/Food/RecallsOutbreaksEmergencies/SafetyAlertsAdvisories/ucm434274.htm (15-05-2016) 44. http://www.food.gov.uk/news-updates/news/2015/13596/undeclared-almond-incident-update (15-05-2016) 45. http://www.inspection.gc.ca/about-the-cfia/newsroom/food-recall-warnings/complete-listing/2013-10-31c/eng/1414813817676/1414813823156 (15-05-2016) 46. http://allergicliving.com/2015/02/14/inside-the-peanut-tainted-cumin-recalls-what-happened/ (15-05-2016) 47. https://www.food.gov.uk/science/allergy-intolerance/label (11-05-2016) 48. http://www.elisa-antibody.com/ELISA-Introduction/ELISA-types (5-05-2016) 49. http://www.elisa-antibody.com/index.php?page=sandwich-elisa (5-05-2016) 50. http://www.bio-rad.com/en-be/applications-technologies/what-real-time-pcr-qpcr (6-05-2016) 51. http://dyes.gene-quantification.info/ (8-05-2016) 52. The European Commission Directive 2007/68/EC (12-05-2016)

http://www.phadia.com/en-US/Products/Products/ImmunoCAP-ISAC/Test-Principle-ImmunoCAP-ISAC/

http://www.phadia.com/en-US/Products/Products/ImmunoCAP-ISAC/Test-Principle-ImmunoCAP-ISAC/

http://www.fda.gov/Food/RecallsOutbreaksEmergencies/SafetyAlertsAdvisories/ucm434274.htm

http://www.fda.gov/Food/RecallsOutbreaksEmergencies/SafetyAlertsAdvisories/ucm434274.htm

http://www.food.gov.uk/news-updates/news/2015/13596/undeclared-almond-incident-update

http://www.food.gov.uk/news-updates/news/2015/13596/undeclared-almond-incident-update

http://www.inspection.gc.ca/about-the-cfia/newsroom/food-recall-warnings/complete-listing/2013-10-31c/eng/1414813817676/1414813823156

http://www.inspection.gc.ca/about-the-cfia/newsroom/food-recall-warnings/complete-listing/2013-10-31c/eng/1414813817676/1414813823156

http://allergicliving.com/2015/02/14/inside-the-peanut-tainted-cumin-recalls-what-happened/

http://allergicliving.com/2015/02/14/inside-the-peanut-tainted-cumin-recalls-what-happened/

https://www.food.gov.uk/science/allergy-intolerance/label

http://www.elisa-antibody.com/ELISA-Introduction/ELISA-types

http://www.elisa-antibody.com/index.php?page=sandwich-elisa

http://www.bio-rad.com/en-be/applications-technologies/what-real-time-pcr-qpcr

http://dyes.gene-quantification.info/

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LECTURES

1. Paediatric drug formulations

It’s a fact that children are not small adults. It’s therefore necessary to adjust the dosage of medication accounting the differences between children and adults. For example: pharmacokinetics changes when we get older. Enzymes their activity changes, decreasing but some of them increasing in time as well. There are regulations(EU/US) that demand from pharmaceutical industries to study the effect of the new medication on children. The benefits are that the pharmaceutical Industries that make these studies get for example a longer exclusivity on the market. The challenge for paediatric formulations is to be acceptable for children, to have easy and safe administration and of course to have a sufficient bioavailability. When we look to the medication given to children and whereby severe adverse reactions occurred. We see that excipients play a major role in these reactions, more than the active compounds. So it’s important not to study just the active compound but also the influence of excipients on the child. What’s the ideal drug formulation for a child? For many years the syrup is the most known drug formulation for children. The question arises if this is the best formulation, because the dosage is in fact subjective. Now there is an evolution changing the common formulations, at the moment mini-tablets, (oro)dispersible (mini-) tablets, orodispersible films are very popular. Challenging is to test these formulations with new methods. There are studies suggesting these formulations are better than the well-known syrup. Nevertheless, these formulations must be accepted by the child. So by considering the flavour, the colour, the size... of the formulation, children will be able to get the measured needed dosage and will be more willing to take the medication.

2. The Pharmacist is a key stakeholder in measuring and managing patients’ adherence to medications

A major problem in patients who get medications is the adherence to these medications. First of all, there is a difference between persistence and adherence. Where persistence is when the medication is taken, adherence has an extra condition and this is when the medication is taken as prescribed. There are three important key elements in adherence. Initiation, implementation and persistence of the medication(s). Each of these factors has their own value, but we can say that implementation plays a big role in the patients’ adherence and that this key element is challenging nowadays. Implementation can we describe as the intake of the correct dose of medication at the prescribed time. If this fails, the consequences can be problematic, for example if a NOAC-dose is missed it has a much bigger effect on the patient than if a cardio-aspirin dose is missed. The problem with adherence is that it’s not studied well in clinical trials. In clinical trials there is a strict follow-up of the patients. On the other hand, in real-life the patients are not or not much adherent to the medication and there are patients who take more than one medication a day which makes the situation more complex. If the adherence fluctuates too much, we see more variability in the pharmacokinetics and pharmacodynamics which can result in toxicity.

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The adherence can be measured with different methods, one more reliable than the other. For example, TDM method is more reliable than a questionnaire, where a patient can lie about his adherence. To control the adherence, we can put an electronic chip in the package of the medication, so we can see if the patient takes his prescribed dose and even more if he takes it at the prescribed moment(future). It’s well-known that if a medication can be given in one dose a day there is a better adherence. But when a patient forgets his medication it has bigger consequences (failure, under dosage...) than when he forgets a dose of a twice a day medication. We can conclude that a poor adherence can lead to a failure of treatment. Thence a disease can progress which on his turn can lead to polypharmacy. Polypharmacy is surely an indicator of poor adherence. So it’s important to improve adherence by improving especially the implementation of medication(s). We have to search to a collective solution where not only the patients play a big role in their own adherence but also the healthcare and the industry.

3. Globalization @Janssen: why would you be interested? In our lives we pass through mainly four stages. It begins with the fact that we are unconsciously incompetent in our actions. Secondly we are competent in doing things but we are not well aware of this. Then competence in doing things has become so obvious that we are doing these unconsciously. This stage is very dangerous in our lives; we can have too much confidence in ourselves that it can be self-damaging. As last we are consciously incompetent, we accept that we aren’t able to do certain things anymore. So it’s obvious that the main purpose in our actions is that we are and stay aware of the things we do. Working at a global company like Johnson&Johnson, you have to be competent but also conscious about the decisions you make. J&J is an important global organization with sites over the whole world and is specialized in medicines, medical devices and research in the health of the people. As a future employee of J&J you will not always achieve that what you have expected. It’s therefore important for the employee to be able to let things go, it’s a process of falling and getting up at J&J. Wim Braeckmans, the senior director of the manufacturing part at J&J, says that the previous saying is a sign of maturity. As senior director, he is in contact with multiple sites in different continents. He is telling us that communication is very important as well as the cultural differences. Diversity in a team is thence better to achieve better results. The manufacturing sites are also dependent on other external manufacturers. The capability and reliability of these firms are decisive aspects for achieving appropriate results afterwards. Another important part is the standardization within a firm makes things a lot easier and can be accomplished with the increase of practices and IT-systems together. From this we can learn that organization is far more important than a strategy. To work as a coherent team is required but also to make decisions by yourself in complex situations. Last, Mr. Braeckmans mentioned there is always good and bad in a (global) company. But early disclosure of the bad, taking care of this and highlighting the good things are necessary to keep a company running.

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4. Individuals with drug problems: “client” in the pharmacy and the court?

Formerly, drug offenders were put immediately in prison when getting caught with drugs. Now, there’s an emerging phenomenon. Drug policy is a better solution for these individuals than just putting them away from society. The USA started with this and it’s already implemented in some countries including Belgium. In 2001, the judicial problem of drug became a public health problem. Focusing on the prevention, repression of drug use and on the aid of the drug users. The aid consists of succession and if there is improvement, the complaints are often dropped. Most of the times drug abuse occurs with other problems. These individuals are not employed. If they have a residence, they are in bad shape, they commit(ted) criminal activities… An overall approach is therefore more important. Pharmacists play a role in the aid of these individuals, this by providing them replacement therapy. Methadone and more and more suboxone are used as substitution for heroin. But the additional use of heroin is still a big challenge to oppose in the future.

detection of specific food allergens in processed food ... · 1.2 food allergy and food intolerance...

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