AGRICULTURAL RESEARCH COMMUNICATION CENTRE

www.arccjournals.comAsian J. Dairy & Food Res.., 33 (4) : 292-296, 2014

doi:10.5958/0976-0563.2014.00619.8

BIOSENSORS FOR FOOD AND DAIRY INDUSTRY

Anant S. Kulkarni* , D.C. Joshi1 and G.P. Tagalpallewar1

Department of Food Processing Technology,A.D. Patel Institute of Technology, Anand 388 121, India

Received: 18-02-2014 Accepted: 31-10-2014

ABSTRACTAnalytical technology based on biosensor is an extremely broad field which has impacts on food

and dairy sector as the online quality control is essential in food and dairy industry and efficientquality assurance is becoming increasingly important. Food producers are increasingly asking forefficient quality control methods to satisfy the consumer and regulatory requirements to improve theproduction feasibility, quality sorting, automation and reduction in production cost and time.Considering all these aspects related to food and dairy industry, the development and use of biosensorhas really became a boon. This paper highlights the basic concepts and applications of biosensor infood and dairy industry.

Key words: Acid, Alcohol, Biosensors, Dairy, Food, Glucose, Milk Urea.

*Corresponding author’s e-mail: anant_food@rediffmail.com,1Faculty of Food processing Technology, AAU, Anand, India

INTRODUCTIONThere is a growing demand for rapid and

simultaneous measurement of quality parameters infood and dairy industry. Industry suffers from thelack of monitoring food and beverage productioncontinuously with a device whose speed, sensitivity,stability, ease of use to exceed the current affinitymethodology (Gurtas, 1997; Mello and Kubota,2002). The lack of appropriate sensors and controlsystems for the food processors is considered as oneof the major impediments to the development of fullyautomated food processing and packaging systems.Safety monitoring and quality allows the assessmentof food safety in real time (Leonard et al., 2003).Hence, online biosensors have been developed forcomputerized process control and provide a goodalternative to other methods which are tedious, timeconsuming and may require expensive instrumentsand reagents in addition to considerable technicalskills (Hogeveen and Ouweltjes, 2004).

The importance of on-line measurementcompared to a laboratory measurement in terms ofprocess control is firstly due to its response time(Ferreira et al. 2003; Richter, 1993). Sampling andsubsequent analysis in a laboratory involves a timedelay, which can be sometimes several days.

Moreover, laboratory analysis is dependent on thesample size and sampling technique. Hence, on-linebiosensors which describe the real time state ofprocess are considered as the better tool for on-lineanalysis and process control.

History: The era of biosensors began in 1950, whena biosensor with an oxygen electrode was developedby L.L. Clark in Cicinati, USA to measure thedissolved oxygen in blood. It is known as Clarkelectrode. Later on glucose oxidase enzyme in a gelwas coated and immobilized on the oxygen electrodeto measure blood sugar. Similarly enzyme ureasewas used for measuring urea in body fluids like bloodand urine. The biosensors based on the use ofenzymes involving catalytic actions are describedas catalytic biosensors. In 1980, the another type ofbiosensors which use affinity between analyte andreceptor, commonly known as bio-affinity biosensorwas developed which make use of antibodies,receptor molecules etc. which have high affinity withanalyte. Later on biosensors based on ELISA havebeen developed using labeled antibody or labeledantigen coupled with a suitable transducer. In 1990,whole cell biosensors were developed making use ofwhole microbial cells or organelle. Recently smallsensing organs like antennule have been used to

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FIG 1: Different parts of biosensor

measure the level of drugs or environmentaltoxicants.

Definition: Biosensors have been defined in severalways as follows,1. A biosensor is a device which responds to thepresence of a specific analyte (a chemical orbiological substance that needs to be measured) byproducing an electrical signal proportional to theconcentration of the analyte (Gurtas, 1997).2. A biosensor may be a device or instrumentcomprising a biological sensing element coupled toa transducer ( Bhadoria and Chaudhary,2011).Using this definition, examples of biological sensingelements might include enzymes, organelles,antibodies, whole cells, DNA and tissue.3. A biosensor may be a self- contained analyticalsystem that responds directly and selectively tobiological important species (Rajasekhar et al.,2005).

Hence, it is device or system that detects abiological event.

Parts of the biosensor: Biosensor consists of a)Receptor b) Transducer c) Amplifier d) Processorand e) Display shown in Fig. 1.

Receptor: It is biologically sensitive part which iscapable of producing a biochemical signal that isconverted by the transducer into the electricalresponse. Molecular recognition of specific samplei.e. analyte by respective receptor works on the lockand key principle. The biological sensitive materialmay be enzyme, proteins, antibodies, DNA,organelles, microbial cells and plant tissue. Receptoris usually immobilized next to transducer within apolyacrylamide, cellulose or suitable gel or an acetylcellulose membrane. Receptor should also have highselectivity for specific compound. Sometimes multi-enzyme biocatalytic membrane is used to increasethe selectivity (Gurtas, 1997).

Transducer: It is the interpreter of biosensor. Itconverts the effects of biocatalitical reaction into such

signals which can be electronically amplified, storedand displayed. Changes in pH, light emission canbe transduced by potentiometric, amperometric oroptoelectronic system due to the effect of biocatalyst(Gurtas, 1997; Dhotre et al., 2006).

Amplifier: The electrical signal from the transduceris often weak with heavy noise. The unwanted noisefrom the signal is removed and the signals areamplified (Thakur and Raghvan, 2013).

Processor: The analogue signal produced byamplifier is usually converted in to digital signal; thedata is processed and converted in to concentrationunits (Dhotre et al., 2006).

Types of biosensors: Biosensors are classified invarious ways.A. Biosensors classified on the basis of transducerused are as follow:* Calorimetric biosensors:-The heat output (orabsorbed) by the reaction.* Potentiometric biosensors:-Changes in thedistribution of charges causing an electrical potentialto be produced.* Amperometric biosensors:-Movement of electronsproduced in a redox reaction.* Optical biosensors:-Light output during thereaction or a light absorbance difference betweenthe reactants and products.* Piezo-electric biosensors:-Effects due to the massof the reactants or products (Leonard et al., 2003).B. Biosensors are classified on the basis biologicalmaterial immobilization:-1. Biosensors based on the immobilization of wholecells used as the biochemical component. The use ofthis type of biosensor can increase the sensor stabilityand render the regeneration of enzyme easier.2. Sensor device coupled with reactors whichcontain an immobilized enzyme matrix. Here theresidual activity of enzyme is evaluated by measuringthe enzymatic product before and after the inhibition.3. Biosensors based on direct enzymeimmobilization on a transducer device. Here theenzyme and the transducer elements are in closecontact with each other and incorporated in singleunit (Leonard et al., 2003).

Evolution of biosensors: Till date the biosensorsare in third generation and these generations areaccording to the degree of integration of thecomponents.

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The first generation sensors are based onenzyme solution held in the reaction chamber by amembrane in front of a slightly recessed indicatorelectrode.

In the second generation of biosensors thereis a direct physical adsorption or covalent fixationof the receptor at the transducer surface, therebyeliminating the inactive membrane layer. These typesof sensors are used for lactose and glucosedetermination.

The thi rd generation biosensor ischaracterized by the immobilization of the receptordirectly onto an electronic element which directlysenses and amplifies changes. This type of biosensoris known as “Biochip” (Schaertel and Ruth,1988).

Ideal requirements of the biosensors: Thebiosensor must possess the ideal characteristics suchas Accuracy, Assay time, Sensitivity, Specificity,Reproducibility, Robust, User friendly, Compatibleinterface, Validation (Leonard et al., 2003).

1) On-line determination of lactoseconcentration in milk: The cascade enzymebiosensor is used for on-line determination of lactosecontent of milk. The enzyme â-galactosidase (GAL)cleaves the disaccharide lactose producing glucoseand galactose. The glucose reacts with glucoseoxidase (GOD) to form H 2O2. Horseradishperoxidase (POD) oxidizes H2O2 with 5-ASA(aminosalicyclic acid) as a mediator. The oxidizedform of the mediator is reduced at the electroderesulting in an amperometric signal proportional tothe lactose concentration (Ferreira et al., 2003 andEshkenazi et al., 2000).

2) Milk urea biosensor: Protein supplements inanimal feeds are costly. There is an efficientconversion of feed protein into milk protein. Excessivelevels of nitrogen derived from feed may increasethe systemic urea concentration of milk withoutincrease in milk production. This high concentrationof urea may impair reproductive performance andalso causes excessive nitrogen in dairy waste whichis environment pollution. The milk urea nitrogen(MUN) data helps in adjusting the nutritionalprogramme of the herd. The normal range of MUNis 5-20 mg/dl.( Edward, 1999).

3) Biosensor for glucose concentration in meat:Measurement of glucose gradient from surface to the

centre of meat so formed is essential to know thequality of meat. As the spoilage advances, theglucose gradient becomes more pronounced.

The biosensor developed is an array of fourglucose electrode (i.e. glucose oxidase in a ferrocenemediated Amperometric sensor) for the measurementof glucose concentration at various depths in a meatsample. The mediator e.g. ferrocene facilitates thetransfer of electrons from the redox centre of enzymeto the surface of the electrode. The resulting glucoseprofile can be related to the expected shelf life of thesample. This biosensor is developed by CranefieldInstitute (Schaertel and Ruth, 1988).

4) Biosensor for organic acid: Among the organicacids present in food i.e. glutamic acid, lactic acidand ascorbic acid are of special importance.

The quality of mozzarella cheese stronglydepends on the acidity of the curd. To control theacidity, biosensor has been used to measure the L-lactic acid. The system consists of an electrochemical(flow-through flow-jet) cell assembled with platinumsensor covered with the immobilized lactate oxidaseenzyme connected to an amperometer.

Lactate + O2 lactate oxidase Pyruvate + H2O2

The amount of lactate in the curd is detectedby H2O2 probe. The real time analysis of lactate allowsthe control of the curd ripening evaluation at differentpasteurization temperature. This method is moresensitive than pH probe (Rajasekhar et al., 2005).

5) Determination of ascorbic acid in fruit juices:Flow injection Potentiometric system has beendeveloped for simultaneous determination ofascorbic acid with other parameters. This system isbased on the reaction of the species with ascorbateoxidase which is immobilized on alkaline glass beadsusing glutaraldehyde. Fall in oxygen consumption isdetected by the electrode. Oxygen consumed isproportional to the ascorbic acid content of thesample (Gurtas,1997 and Eshkenazi et al,2000).

6) Alcohol biosensor: Online measurement of ethylalcohol or methanol during fermentation and yeastcultivation is very important to minimize productinhibition and increase yield. Many micro-organismsuse alcohols as carbon source, its concentration canbe determined from the respiration activity of thecells. The respiration activity is directly measuredby oxygen electrode.

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The biosensor system consists of immobilizedyeast or bacteria, a gas permeable membrane (Teflon)and an oxygen electrode. Porous membrane retainingmicrobial cells is fixed on the surface of Teflonmembrane of the electrode. Thus, the cells aretrapped between the two membranes. A gaspermeable membrane is placed on the surface ofelectrode and covered with nylon net. Thesemembranes are fastened with rubber –o-rings. Thesteady state current obtained depend on theconcentration of ethanol / methanol. The responsetime is 10 min at 30OC (Rajasekhar et al., 2005).

Methanol + O2 H2O2 + FormaldehydeEthanol + O2 H2O2 + Acetaldehyde

7) Microbial biosensors: These are used todetermine the cell population in fermentors,fermented products and washed water. In microbialbiosensors electrochemical transducer is used asthey generate current when they are in contact withelectrode (generation electrode and referenceelectrode are generally preferred) (Leonard et al.,2003).

8) Tea biosensor: Polyphenols are strongantioxidants present in tea, hence more importantfrom nutrition point of view. To know the quantity ofpolyphenols in the tea an enzyme basedamperometric biosensor has been developed(Thakur and Raghvan, 2013).

9) Detection of pathogens: Harmful microbescan contaminate food and water and cause manyinfectious diseases in both animals and humans.Some of the most commonly used biosensor systemsfor the detection of pathogens in food and waterinclude surface plasma resonance (SPR),amperometric, potentiometric, and acoustic wavesensors (Narsaiah et al., 2012).

Advantages: Many batch operations in the foodindustry are being replaced by continuous processhaving high degree of automation. Thus, there is anincreasing demand for instruments suitable forautomatic quality control throughout the process andat the end of the line. Use of biosensors not onlyincrease the food safety but also provide cost effectivecontrol, less employment, time and energy savings,little sample consumption , high sampling rates and

relatively flexible, rapid monitoring of the processwith speed, sensitivity and stability (Gurtas, 1997;Kennedy et al., 2005).Disadvantages: Biosensors have not been usedextensively for on-line processing because they arecomposed of biological material which causesproblem in sterilization or may be inactivated bystrong acids or bases. In addition biosensors have alimited testing life because of biological character oftheir design (Gurtas, 1997; Kennedy et al., 2005).

Practical Applications: In food and dairy industry,the uses of biosensor for online monitoring of qualityparameters are widespread and their demand isincreasing due to the automation. The present reviewpaper represents the basic information on biosensorsand their application in food and dairy industry.

Future use of biosensors: The emergence ofbiosensors from the research lab to the market placeor industry is very slow, there is a big potential foron-line monitoring of raw materials, tracecompounds, vitamins, flavours, additives andcontaminants. In future, on-line use of biosensorsprovides feedback control of both the componentand microbial levels of these and similar processesby continual on-line monitoring. Quality control infood and dairy industry still relies on human sensessuch as smell, sight and taste. Quality control ofmicrobial spoilage, oxidative rancidity and fruitripening by tasting may be replaced by biosensors(Gurtas, 1997; Evangelyn and Stephen, 2003).

Though biosensors are not cheap today butin due course of time due to their wide applicationsmay become cheap. The cost of biosensor dependsupon its design for the specific parameter to beanalyze and the biological component to be used.Looking to the scope, need, applications andadvantages of biosensors in food and dairy industrythese are economically viable.

CONCLUSIONThere is a vast market potential for biosensors

for analysis and control of biological systems. It iscapable to hold a promise of revolutionizing manyaspects of food and dairy industry and may satisfysome of the most essential needs of measurements ofon-line food quality attributes.

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