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Annex A: Food components
A.1 Structure of food macromolecules
This annex contains a summary of the chemical structures of the main macromole-
cules in foods, the properties, functions and sources of vitamins and minerals, and
examples of functional components of foods. More detailed information may be
found in food chemistry texts (e.g. Belitz et al., 2009; Damodaran et al., 2007) and
nutrition texts (e.g. Webster-Gandy et al., 2011; Gibney et al., 2009).
A.1.1 Carbohydrates
A.1.1.1 Sugars
Sugars may be single molecules, known as ‘monosaccharides’, which can be classi-
fied by the number of carbon atoms they contain: diose (2), triose (3), tetrose (4),
pentose (5), hexose (6), heptose (7). Two or three monosaccharides joined together
are termed ‘disaccharides’ and ‘trisaccharides’, respectively. ‘Oligosaccharides’
have up to 20 monosaccharides, joined by glycosidic bonds, and ‘polysaccharides’
are carbohydrates that contain more than 20 monosaccharides, joined by different
types of glycosidic bonds. Monosaccharides contain both hydroxyl groups and
carbonyl groups and are classified as ‘aldoses’ if the carbonyl group is an aldehyde
(e.g. pentose (five carbon atoms), or hexose (six carbon atoms)) or ‘ketoses’ if it is
a ketone (e.g. the corresponding five- and six-carbon molecules are pentulose, hexu-
lose). When the position of the aldehyde or ketone group on the molecule allows it
to react with oxidants (i.e. act as a reducing agent as, for example in Maillard reac-
tions), the sugar is known as a ‘reducing sugar’. Examples include glucose, fructose
and arabinose, and the disaccharides lactose and maltose, but not sucrose, which is
a nonreducing sugar. Reaction between the carbonyl and hydroxyl groups in the
molecule forms monosaccharides into a ring structure. Common types have five-
membered (furanose) rings or six-membered (pyranose) rings (Fig. A1).
In solution, sugars have an equilibrium mixture of open-chain and closed-ring
(or cyclic) structures. In the open-chain form, the carbon atom that has the C5O
bond is the carbonyl atom, whereas in the cyclic structure the carbonyl atom is
attached to the O of the ring and an OH group. Monosaccharides also contain ‘chi-
ral’ carbon atoms (atoms that can exist in two different spatial configurations that
are the mirror image of each other). Glucose is the most abundant aldose and the
two forms are D- and L-glucose, with the D-form occurring naturally in foods. Other
common naturally occurring monosaccharides are D-mannose, D-galactose and D-
xylose. The L-form is less common in nature, but two examples are L-arabinose and
L-galactose, which are units in polymeric carbohydrates. The only ketose found nat-
urally in foods is D-fructose (fruit sugar), which forms � 55% of high-fructose
corn syrup and � 40% of honey. Further details of the structure and orientation of
monosaccharide molecules are given by BeMiller and Whistler (1996) and the
important reactions of monosaccharides are described by Davis and Fairbanks
(2002).
A.1.1.2 Glycogen and starch
Glycogen is a branched glucose polymer that has glucose molecules linked by
α(1�4) glycosidic bonds. Starch occurs in two forms: (1) α-amylose, in which
500�20,000 D-glucose molecules are linked by α(1�4) glycosidic bonds
(Fig. A2A) in linear, helical chains; and (2) amylopectin, in which highly branched
chains of up to 30 glucose molecules are linked through α(1�4) bonds and con-
nected to each other through α(1�6) branch points. Amylopectin is therefore a
much larger molecule than amylose, typically containing 1�2 million residues,
with a mass that is four to five times that of amylose. Starch granules produce low-
viscosity pumpable slurries in cold water, and thicken due to gelatinisation when
heated to � 80�C. Details of starch gelatinisation are given by Maaruf et al. (2001),
Palav and Seetharaman (2006) and Xie et al. (2006).
A.1.1.3 Cellulose
Cellulose is composed of unbranched linear chains of 1000�10,000 D-glucose
molecules, linked together by β(1�4) glycosidic bonds (Fig. A2B). The linear struc-
ture promotes hydrogen bonding that holds together nearby cellulose molecules to
form a three-dimensional structure of microfibres, which in turn interact to form
cellulose fibres. A typical fibre contains � 500,000 cellulose molecules, and the
large number of hydrogen bonds creates a crystalline structure that has a high ten-
sile strength. As a result, cellulose is a stiff material that is used by plants as a
structural molecule to support leaves and stems. In contrast to other more amor-
phous polymeric carbohydrates, the crystalline structure also makes cellulose
CH2OH CH2OH CH2OH
HH
OHH
OH
HH
OH
H
OHOH
H
HO
O
O
OH
H
(A) (B)
Figure A1 Structure of (A) a furanose ring and (B) a pyranose ring.
e2 Annex A: Food components
insoluble and resistant to enzymic breakdown, a property that also makes cellulose
suitable as a packaging film (see Section 24.2.4). Additional details of the proper-
ties of cellulose are given by Chaplin (2014). Carboxymethylcellulose (CMC) is
produced by the reaction of cellulose with chloroacetic acid to substitute polar car-
boxyl groups for hydroxyl groups. This makes the cellulose soluble and more chem-
ically reactive. The functional properties of CMC depend on how many hydroxyl
groups are involved in the substitution reaction and the chain length of the cellulose
backbone.
A.1.1.4 Polysaccharide gums
Hydrocolloids (Table A1) are linear or branched polysaccharides that increase vis-
cosity depending on the molecular weight, shape and flexibility of the hydrated
molecules. Also, the presence of electrically charged groups causes mutual repul-
sion of molecular chains that extends them to create higher viscosities (e.g. algi-
nates, carrageenans and xanthan gums). When they are used to form gels, the
polysaccharide molecules come out of solution to form a three-dimensional network
that is joined together by hydrogen bonding, hydrophobic van der Waals associa-
tions, ionic crosslinking or covalent bonding. Guar and locust bean (or carob) gums
CH2OH
H
HH
OH
H
OH
OH
Hn
O
CH2OH
H
HH
OH
OH
OH
H
O
CH2OH
CH2OH
beta (1→ 4) bondcellulose
H
HH
OH
OH
OH
OH
H
O
(A)
(B)
OCH2OH
O
O
CH2OH
alpha (1→ 4) bondstarch, glycogen
OCH2OH
O
O
Figure A2 Structure of polysaccharides: (A) α(1�4) bonds in starch and glycogen and
(B) β(1�4) glycosidic bonds in cellulose (n is the number of repeating glucose units).
e3Annex A: Food components
Table
A1Properties
ofaselectionofhydrocolloids
Hydrocolloid
pH
range
Solubility
at21� C
and65� C
Effectofion/salt
Gel
character
Acidstability
Alginates
Carrageenan
3.5�1
0Yes
Yes
Ca2
1required
forgel
Rigid/cutable/
cohesive/
thixotropic
Gelsat
pH
3.5
withcalcium
present
Kappa
4�1
0No
Yes
K1gels
Rigid/cutable
Cohesive/
thixotropic
Solutionsundergohydrolysisat
pH
3.5;gel
isstable
Iota
4�1
0No
Yes
Ca2
1gels
Lam
bda
4�1
0Yes
Yes
None
Carboxylmethylcellulose
(CMC)
4�1
0Yes
Yes
Decreases
viscosity
None
Stable
atpH
7�9
.Lower
viscosity
at
pH
5,precipitates
inmilk
(pH
,3;.6)
Gelatin
4.5�1
0Yes
Yes
None
Cutable/elastic
Stable
Gellangum
(tetra-saccharide-2
glucose1glucuronic
acid
and
rham
nose)
1�1
3No
Yes
Required
forgel
Rigid/cutable/
cohesive
Stable
inacid
conditions
Guar
gum
4�1
0Yes
Yes
None
None
Gradual
declineat
pH
3.5�1
0
Gum
Arabic
2�1
0Yes
Yes
None
None
Stable
Locustbeangum
4�1
0No
Yes
None
None(gelswith
xanthan
gum)
Stable
atpH
5�8
Micro-crystallinecellulose
(MCC)
3�1
0Yes
Yes
None
None
Insoluble
Methylcellulose
(MC)andhydroxypropyl
methylcellulose
(HPMC)
3�1
0Yes
No
None
Rigid/cutable
Stable
inacid
conditions
Pectins
2�7
No
Yes
HM
a;none
Rigid/cutable
Cohesive/
thixotropic
Stable
gelsform
edin
presence
of
sugar
andacid
orwithCa2
1LM
a;Ca2
1gels
Xanthan
1�1
3No
Yes
None
None(gelswith
locustbeangum)
Precipitationin
milk
(pH
,4.5)
aHighmethoxylandlow
methoxylpectins.
Source:
Adaptedfrom
Univar,2005.Hydrocolloids.Univar
USA
Inc.Available
at:,www.univar.com/en/Canada/Industries/Food-Ingredients.aspx.,select
‘Texture
modification’(lastaccessed
February2016);
BeM
iller,J.N.,Whistler,R.L.,1996.Carbohydrates.In:Fennem
a,O.R.(Ed.),FoodChem
istry,3rd
ed.MarcelDekker,New
York,pp.157�2
23.
are thickening agents, whose main component is a galactomannan consisting of a
chain of β-D-mannopyranosyl units joined by (1�4) bonds with α-D-galactopyrano-syl branches. Xanthan gum is composed of chains that are identical to cellulose, but
with trisaccharide side-chains of mannopyranosyl and glucuronopyranosyl units.
Carrageenans are a group of .100 types of sulphated galactans that are derived
from seaweed. The basic structure has chains of D-galactopyranosyl units that have
alternating (1�3)-α-D and (1�4)-β-D-glycosidic linkages with sulphate groups
esterified to the hydroxyl groups. The three basic types are named ‘kappa’, ‘iota’
and ‘lambda’, which form gels with potassium or calcium ions. Alginates are the
sodium salt of alginic acid, a polyuronic acid composed of units of β-D-mannopyra-
nosyluronic acid and α-DL-gulopyranosyluronic acid.Pectins are a group of poly-α-D-galactopyranosyluronic acids that have differing
amounts of methyl ester groups along the chains. High-methoxyl pectins have more
than half the carboxyl groups that methyl esters have, whereas low-methoxyl pec-
tins have less that half the carboxyl groups of methyl esters and form gels with cal-
cium ions. Gum arabic has two fractions: highly branched arabinogalactan chains
with side chains of galactopyranosyl units, and another fraction that has proteins as
an integral part of the structure.
A.1.2 Lipids
Lipids are mono-, di- and triesters of glycerol with fatty acids (monocarboxylic
acids). Glycerol is a trihydric alcohol (containing three hydroxyl (�OH) groups that
can combine with up to three fatty acids to form a wide variety of monoacylglycer-
ols, diacylglycerols or triacylglycerols) (Fig. A3). A monoacylglycerol has one fatty
acid unit per molecule of glycerol, which may be attached to carbon atom 1 or 2 on
the glycerol molecule; a diacylglycerol has two fatty acids as either the 1,2 form or
the 1,3 form depending on how they are attached to the glycerol molecule.
Triacylglycerols are the main constituents of vegetable oils and animal fats, and
(A) (B)
(C) (D)
CH3(CH2)7-C=C-(CH2)7-C-OH
CH3(CH2)7CH=CH(CH2)7C(O)O-CH2
CH3(CH2)14C(O)O-CH2
CH3(CH2)14C(O)O-CH2
HO-CH
HO-CH
HO-CH2
||||
|
|
CH3(CH2)7CH=CH(CH2)7C(O)O-CH2
CH3(CH2)14C(O)O-CH2
CH3(CH2)7CH=CH(CH2)7C(O)O-CH|
|
OH H
Figure A3 Components of lipids: (A) oleic acid; (B) 1-monoacylglyceride;
(C) 1,3-diacylglyceride and (D) triacylglyceride.
e5Annex A: Food components
their structure involves a chain of carbon atoms with a carboxyl group (�COOH) at
one end. The triacylglyceride structural formula (Fig. A3D showing olive oil) con-
sists of two radicals of oleic acid and one of palmitic acid attached to the glycerol
molecule (the vertical chain of carbon atoms). Saturated fatty acids (SFAs) have no
double bonds between the carbon atoms, monounsaturated fatty acids (MUFAs)
have only one double bond, and polyunsaturated fatty acids (PUFAs) have more
than one double bond. Nawar (1996) has reviewed different forms of nomenclature
of lipids and in this book the common names for fats and fatty acids are normally
used (Table A2). The numbers at the beginning of the scientific names indicate the
locations of the double bonds. By convention, the carbon atom of the carboxyl
group is number one and Greek numbers such as ‘di, tri, tetra, penta, and hexa’ are
used to describe the length of carbon chains. For example, linoleic acid is 9,12-
octadecadienoic acid, which indicates that there is an 18-carbon atom chain (octa
deca) with two double bonds (di en) located at carbon atoms 9 and 12, with carbon
atom 1 being a carboxyl group (oic acid).
The structural formula corresponds to:
CH3CH2CH2CH2CH2CH5CHCH2CH5CHCH2CH2CH2CH2CH2CH2CH2COOH
which can be abbreviated as
CH3ðCH2Þ4CH5CHCH2CH5CHðCH2Þ7COOH
Fatty acids can also be written as, for example C18:2, which indicates that the
fatty acid consists of an 18-carbon atom chain with two double bonds. Although
this could describe a number of possible fatty acids that have this chemical compo-
sition, in common use it shows the naturally occurring fatty acid (i.e. linoleic acid).
Double bonds are ‘conjugated’ when they are separated from each other by one
single bond (e.g. �CH5CH�CH5CH�) so 9,11-conjugated linoleic acid has the
formula:
CH3ðCH2Þ5CH5CH2CH5CHðCH2Þ7COOH
‘Configurational isomers’ are described by Latin prefixes ‘cis’ (on the same
side) and ‘trans’ (on the other side) to indicate the orientation of hydrogen atoms to
the double bond. Naturally occurring fatty acids mostly have the cis-configuration.
Fats crystallise below their melting point in a two-stage process: nucleation fol-
lowed by crystal growth. Details of this process in relation to water are described
in Section 22.1.1, but fats also crystallise in a similar way. The size and shape of
crystals depends on the temperature but are also influenced by minor components
in the oil (e.g., free fatty acids) and by stirring. Lipids can also be polymorphic;
adopting different crystal morphologies and changing from one form to another
without melting. These transformations take place to produce the more
stable forms of the crystals. The factors that determine the type of polymorphic
e6 Annex A: Food components
Table
A2Chem
icalnames
anddescriptionsofsomecommonfattyacids
Chem
icalnames
anddescriptionsofsomecommonfattyacids
Commonname
Carbonatoms
Double
bonds
Scientificname
Sources
Butyricacid
40
Butanoic
acid
Butterfat
Caproic
acid
60
Hexanoic
acid
Butterfat
Caprylicacid
80
Octanoic
acid
Coconutoil
Capricacid
10
0Decanoic
acid
Coconutoil
Lauricacid
12
0Dodecanoic
acid
Coconutoil
Myristic
acid
14
0Tetradecanoic
acid
Palm
kernel
oil
Palmitic
acid
16
0Hexadecanoic
acid
Palm
oil
Palmitoleic
acid
16
19-H
exadecenoic
acid
Anim
alfats
Stearic
acid
18
0Octadecanoic
acid
Anim
alfats
Oleic
acid
18
19-O
ctadecenoic
acid
Oliveoil
Ricinoleic
acid
18
112-H
ydroxy-9-octadecenoic
acid
Castoroil
Vaccenic
acid
18
111-O
ctadecenoic
acid
Butterfat
Linoleic
acid
18
29,12-O
ctadecadienoic
acid
Grapeseed
oil
α-Linolenic
acid
(ALA)
18
39,12,15-O
ctadecatrienoic
acid
Flaxseed
(linseed)oil
γ-Linolenic
acid
(GLA)
18
36,9,12-O
ctadecatrienoic
acid
Borageoil
Arachidic
acid
20
0Eicosanoic
acid
Peanutoil,fish
oil
Gadoleic
acid
20
19-Eicosenoic
acid
Fishoil
Arachidonic
acid
(AA)
20
45,8,11,14-Eicosatetraenoic
acid
Liver
fats
EPA
20
55,8,11,14,17-Eicosapentaenoic
acid
Fishoil
Behenic
acid
22
0Docosanoic
acid
Rapeseed(canola)oil
Erucicacid
22
113-D
ocosenoic
acid
Rapeseedoil
DHA
22
64,7,10,13,16,19-D
ocosahexaenoic
acid
Fishoil
Lignocericacid
24
0Tetracosanoic
acid
Smallam
ountsin
mostfats
Source:
From
Zam
ora,A.,2016.Fats,Oils,Fatty
Acids,Triglycerides.Available
at:,www.scientificpsychic.com/fitness/fattyacids.htm
l.(lastaccessed
February2016).
form include temperature and rate of cooling, the purity of the oil and the pres-
ence of crystalline nucleii. Details of polymorphism in cocoa butter used in choc-
olate manufacture are given in Section 5.3.1. Greek letters (α to ω) are used to
identify the location of the double bonds, with the α-carbon atom being closest to
the carboxyl group (carbon atom 2), and the ω-carbon atom being the last in the
chain. Using the example of linoleic acid, this is an ω6 fatty acid because it has a
double bond that is six carbon atoms away from the ω carbon atom. Similarly,
α-linolenic acid is an ω3 fatty acid because it has a double bond three carbon
atoms away from the ω carbon atom (Fig. A4). The classification can be found by
subtracting the highest double-bond location in the scientific name from the num-
ber of carbon atoms in the fatty acid chain. Crops are bred to contain high levels
of monounsaturated or polyunsaturated fatty acids (e.g. oleic types of safflower
oil have � 78% monounsaturated, 15% polyunsaturated, and 7% saturated fatty
acids) (Table A3; see also Section 18.3).
A.1.2.1 Phospholipids
Phospholipids, including lecithin and cephalin, are natural emulsifiers that consist
of an alcohol, such as glycerol, fatty acids and a phosphoric acid compound.
Lecithin has a mixture of diacylglycerides of stearic, palmitic and oleic acids that
are linked to the choline ester of phosphoric acid. Phospholipids are present in cell
walls and other membranes where the fatty acid tails are oriented toward each other
and the phosphate groups form the outer surfaces of the membrane. These semiper-
meable bilipid layers regulate the type of molecules that can pass through the
membrane.
A.1.3 Amino acids and proteins
Amino acids are the units from which proteins are formed. An amino acid consists
of a central (α) carbon atom to which are bound an amino (NH2) group, a hydrogen
atom, a carboxyl (COOH) group and a side chain (R). Each amino acid has a simi-
lar, yet unique structure. The different side chains vary in their complexity and
(A)
(B)
1215ω 9
12 9
ω
1COOH
1COOH
Linoleic acid (omega-6)
Alpha-linoleic acid (omega-3)
Figure A4 Structure of (A) linoleic acid and (B) α-linolenic acid.
e8 Annex A: Food components
Table
A3Fattyacidcompositionofsomecommonedible
fats
andoils
Oilorfat
Ratio:
unsaturated/
saturated
Per
centbyweightoftotalfattyacids
Saturated
Monounsaturated
Polyunsaturated
Capric
acid
C10:0
Lauric
acid
C12:0
Myristic
acid
C14:0
Palm
itic
acid
C16:0
Stearic
acid
C18:0
Oleic
acidC18:1
Linoleic
acid(ω
6)
C18:2
α-linolenic
acid(ω
3)
C18:3
Alm
ond
9.7
��
�7
269
17
�Beeftallow
0.9
��
324
19
43
31
Butterfat(cow)
0.5
33
11
27
12
29
21
Cocoabutter
0.6
��
�25
38
32
3�
Coconut
0.1
647
18
93
62
�Codliver
2.9
��
817
�22
5�
Cottonseed
2.8
��
122
319
54
1
Flaxseed
9.0
��
�3
721
16
53
Grapeseed
7.3
��
�8
415
73
�Lard(pork
fat)
1.2
��
226
14
44
10
�Maize
(corn)
6.7
��
�11
228
58
1
Olive
4.6
��
�13
371
10
1
Palm
1.0
��
145
440
10
�Palm
kernel
0.2
448
16
83
15
2�
Palmolein
1.3
��
137
446
11
�Peanut(groundnut)
4.0
��
�11
248
32
�Rapeseed
15.7
��
�4
262
22
10
Safflower
a10.1
��
�7
213
78
�Sesam
e6.6
��
�9
441
45
�Soybean
5.7
��
�11
424
54
7
Sunflower
a7.3
��
�7
519
68
1
Walnut
5.3
��
�11
528
51
5
Palm
olein
istheliquid
oilobtained
byfractionationofpalm
oilaftercrystallisationat
controlled
temperatures.
Note:Thereisconsiderablevariationin
compositionbetweenvarieties
ofcropsoranim
als.Averagevalues
areused.Percentages
may
notequal100%
dueto
roundingandother
constituentsnotlisted.
aNothigh-oleic
variety.
Source:
Adaptedfrom
Zam
ora,A.,2016.Fats,Oils,Fatty
Acids,Triglycerides.Available
at:,www.scientificpsychic.com/fitness/fattyacids.htm
l.(lastaccessed
February2016).
properties and produce amino acids that have different physicochemical properties.
Amino acids can be classified by the chemical nature of the side chains into two
groups: polar (or hydrophilic) side chains that interact with water; and nonpolar (or
hydrophobic) types that do not react with water. Polar amino acids are: arginine,
asparagine, aspartic acid (or aspartate), glutamine, glutamic acid (or glutamate), his-
tidine, lysine, serine and threonine. Nonpolar amino acids are: alanine, cysteine,
glycine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan, tyro-
sine and valine. Amino acids can also be grouped into those that have ionisable
side chains (e.g. arginine, aspartate, cysteine, glutamate, histidine, lysine and tyro-
sine). These amino acids contribute to the charge exhibited by peptides and pro-
teins. Both the amino group and the carboxyl group of each amino acid are
ionisable and the acid dissociation constants (pKa values, see Section 1.1.3) of
amino acid side chains are important for the activity of enzymes and the stability of
proteins. This is because ionisation alters their physical properties such as solubility
and lipophilicity. At physiological pH, amino acids exist as ‘zwitterions’ that have
a negatively charged carboxyl group and a positively charged amino group.
Examples of pKa values of amino acid side chains are given in Table A4. The
α-carbon of amino acids is chiral, which produces two optically active forms, desig-
nated D- and L-forms. The L-forms are most common, although some peptides con-
tain both D- and L-amino acids. Proteins are also chiral and consist of only L-amino
acids, which is important in understanding their function (e.g. some enzymes bind
one stereoisomer of a compound with a thousand times greater affinity than the
other). A covalent peptide bond is formed by dehydration between the carbon atom
in the carboxyl group of one amino acid to the nitrogen atom of the amino group of
another amino acid (Fig. A5).
Peptides are formed by linking amino acids via amide bonds. Amides are made
by condensing together a carboxylic acid and an amine. Peptides that contain ,25
amino acids are ‘oligopeptides’ and longer peptides are ‘polypeptides’. Peptides
have a polarity, with a free amino group on the amino-terminal residue and a free
carboxyl group on the carboxyl-terminal residue (Fig. A6), both of which are ioni-
sable groups. There may also be ionisable groups in the side chains of some amino
acids. The overall charge on a peptide (or protein) is the sum of the charges of each
Table A4 Examples of acid dissociation constants of amino acidside chains
Amino acid pKa Functional group
Arginine 12.0 Guanidinium
Aspartate and glutamate 4.4 Carboxyl
Cysteine 8.5 Sulphydryl
Histidine 6.5 Imidazole
Lysine 10.0 Amine
Tyrosine 10.0 Phenol
Source: Adapted from Gorga, F.R., 2007. Introduction to protein structure. Available at: ,http://webhost.bridgew.edu/fgorga/proteins/default.htm. (last accessed February 2016).
e10 Annex A: Food components
ionisable group, and depends on its amino acid content and the pH of the solution.
When the pH of a solution equals the pKa of an ionisable group, the group exists as
an equal mixture of its acidic form and the conjugate base. The pH at which a zwit-
terion is neutral is known as the ‘isoelectric point’. If the pH is less than the pKa,
(A)
(B)
R1 OH
O
Cα C
H
H2N
R1 H
Cα
C
O O
NH NHCH C
R
C N
H O
H2N
R2 OH
O
Cα C
H
R2 OH
O
Cα C
H
peptide bond
H2N+
H2O+
rotationrestricted
rotationpossible
Figure A5 (A) Formation of a peptide bond between two amino acid residues and
(B) rotation of peptide bond.
NH2 – CH – C – NH – CH – C – NH – CH – C – NH – CH – C – OH
O
R1 R2 R3 R4
O O O
amino-terminalor
N-terminalresidue
carboxy-terminalor
C-terminalresidue
Figure A6 A tetrapeptide showing a free amino group on the amino-terminal residue and
free carboxyl group on the carboxyl-terminal residue of an amino acid.
e11Annex A: Food components
the acid form predominates, whereas a pH greater than the pKa enables the base to
predominate. The further the pH is from the pKa the more unbalanced are the acid
and base groups.
A protein has a series of amino acid residues linked by peptide bonds, with a
‘backbone’ made up by the repeated sequence of three atoms of each amino acid
residue (the amide N, the α carbon and the carbonyl carbon). Because the bond
between the carbonyl carbon and the nitrogen is a partial double bond, rotation
around this bond is restricted and the peptide unit has a rigid structure (Fig. A5).
Rotation in the peptide backbone is restricted to bonds involving the α-carbon and
the chain can rotate to create three-dimensional structures in proteins. There are
four levels of structure that can be described as:
1. Primary structure (the sequence of amino acid residues in the polypeptide chain, which is
determined by the gene that encodes it)
2. Secondary structure (formed by hydrogen bonds between backbone atoms in a chain, pro-
ducing two types of stable structures: α-helices and β-sheets)3. Tertiary structure (the arrangement of α-helices, β-sheets and random coils along a poly-
peptide chain. The polypeptide folds so that the side chains of nonpolar amino acids are
within the structure and the side chains of polar residues are exposed on the outer surface.
The tertiary structure of some proteins is stabilised by disulphide bonds between cysteine
residues)
4. Quaternary structure (the spatial organisation of chains if there are more than one poly-
peptide chain in a complex protein). Not all proteins show a quaternary structure and in
many the polypeptides fold independently into a stable tertiary structure with the folded
units associating with each other to form the final structure. In contrast, quaternary struc-
tures are stabilised by noncovalent interactions including hydrogen bonding, van der
Walls interactions and ionic bonding. These intricate three-dimensional structures are
unique to each protein and it is these that allow proteins to function. Most globular pro-
teins consist of a core composed mainly of hydrophobic residues surrounded by a skin of
mainly hydrophilic residues. Disulphide bonds are formed by the oxidation of thiol (�SH)
groups in cysteine residues (Fig. A7) and they can occur within a single polypeptide chain
where they stabilise the tertiary structures, or between two chains, where they stabilise
quaternary structures.
HS
“H2”-
SH
S S
Figure A7 Disulphide bond formation.
e12 Annex A: Food components
The wide variety of protein configurations is due to the large number of different
sequences of amino acid residues, which by convention is written with the amino
terminus on the left and the carboxyl terminus on the right. Amino acid sequences
can be written using either a three-letter code or a one-letter code (see Table 1.8).
For example, the code for a small eight-residue peptide is written as:
Asp�Ile�Glu�Phe�Arg�Val�Leu�His. de Jongh and Broersen (2012) review
the different types of protein modification including phosphorylation (attachment of
phosphate to serine, tyrosine or threonine), methylation (attachment of a methyl
group to arginine or the N-terminus of the protein), glycosylation (attachment of
carbohydrates to lysine or the N-terminus) and acetylation (attachment of acetyl to
an amino group such as lysine or the N-terminus).
A.2 Vitamins and minerals
Tables A5 and A6 give a summary of the properties, functions and sources of vita-
mins and minerals.
Arsenic is essential in trace amounts; its deficiency depresses growth and impairs
reproduction. Boron may affect the metabolism of calcium and magnesium, mem-
brane function and prevents some forms of cardiovascular disease. Its deficiency is
linked to osteoporosis and arthritis and may be related to vitamin D production.
Chlorine is essential in maintaining cellular fluid and electrolyte balances and its
deficiency can cause hair and tooth loss, poor muscular contraction and impaired
digestion. Cobalt is an integral part of vitamin B12 and deficiency may lead to per-
nicious anaemia, retarded growth and nervous disorders. Fluorine is incorporated
into bones and teeth and may increase the deposition of calcium. However, at high
levels, it is toxic and has adverse effects on many enzyme systems. Gallium con-
trols brain chemistry and may have antitumour activity. Lithium controls aggres-
siveness. Silicon is needed for production of connective tissues (tendons, cartilage,
blood vessels, nails, skin and hair) and with calcium to makes bones. Tin supports
hair growth and can enhance reflexes. Deficiency symptoms include baldness,
reduced response to loud noises and reduced haemoglobin synthesis. Vanadium is
required for development of bones, cartilage and teeth and for cellular metabolism.
Deficiency may be linked to reproductive problems and kidney disease.
Lanthanum, praeseodymium, neodymium, thulium, samarium, europium and ytter-
bium are each involved in enhanced cell growth and extended lifespan.
A.3 Functional components of foods
Table A7 shows examples of the sources and potential benefits of selected func-
tional components of foods.
e13Annex A: Food components
Table
A5Nature,properties,functionsandsources
ofvitamins
Vitamin
Nature,properties
andfunctions
Main
sources
Deficiency
diseases
Water-soluble
vitamins
Vitam
inC
(ascorbic
acid)
Occurs
asboth
ascorbic
acid
and
dehydroascorbic
acid.A
major
functionissynthesisof
hydroxyproline,acomponentof
collagen
andconnectivetissues.
Essential
forgrowth
ofcartilage,
bones,teethandforwoundhealing.It
isan
antioxidant,helpsabsorb
iron
andmaintain
healthytissues
Nearlyallfreshfruitsandvegetables,
especiallyberries,citrusfruits,green
vegetables,tomatoes
andleafygreen
vegetables
Scurvy,anaemia,capillary
wallrupture/
bruising,nosebleeds,bleedinggums,
low
infectionresistance,muscle
degeneration,poordigestion,
weakened
cartilages
andslow-healing
wounds
Thiamine
(vitam
inB1)
Thiaminepyrophosphateisacoenzyme
forseveral
enzymes
involved
in
decarboxylationreactions(e.g.
decarboxylationofpyruvate)
for
metabolism
ofcarbohydratesinto
energy.Essential
forcorrectheart
functionandhealthynervecells
Meats,dairy
products,leafygreen
vegetables,grainsandlegumes
Polyneuritis,encephalopathy,infantile
beriberi,oedem
a,abdominal
pain,
problemswithmuscle
tonein
the
gastrointestinal
tract,vomiting,
nervoussystem
disorders,seizures,
palpitations,tachycardia,circulatory
collapse,andim
munesystem
problems
Riboflavin
(vitam
inB2)
Precursorto
thecoenzymes
flavin
adeninedinucleotide(FAD)and
flavin
mononucleotide(FMN),which
arehydrogen
carriers
inanumber
of
oxidation�r
eductionreactionswithin
mitochondria.Im
portantforbody
growth
andproductionofredblood
cells
Widevariety
offoods,includingmilk,
meatsandgrains
Ariboflavinosiswithsimilaritiesto
niacindeficiency
(sore
throat
with
swellingofthemouth
andthroat
mucosa,crackingoflipsandmouth,
moistscalyskin,anddecreased
red
bloodcellcountwithnorm
alcellsize
andhaemoglobin
content)
Niacin
(nicotinam
ide)
Precursorto
thecoenzymes
nicotinam
ideadeninedinucleotide
(NAD)andnicotinam
ideadenine
dinucleotidephosphate(N
ADPH),
whicharehydrogen
carriers
in
processes
such
asglycolysis,Kreb’s
cycleandoxidativephosphorylation.
Cholesterol-loweringeffects
Meats,fish,dairy
products,leafygreen
vegetables,potatoes
andnuts.Can
be
synthesised
inthebodyin
small
amountsfrom
tryptophan
Pellagra,whichaffectstheskin,central
nervoussystem
andgastrointestinal
tract(dem
entia,dermatitisand
diarrhoea)
Pyridoxine
(Vitam
inB6)
Occurs
inthreeform
s:pyridoxine,
pyridoxal
andpyridoxam
ine.The
precursorto
pyridoxal
phosphate,a
coenzymeforseveral
reactions
involvingprotein
metabolism
,
includingtransaminationreactions
necessary
forsynthesisofam
ino
acids.Helpsform
redbloodcellsand
maintain
brain
function
Pyridoxal
andpyridoxam
inein
meat,
milk,fish
andpoultry,and
pyridoxine,pyridoxal
inanumber
of
vegetablesincludingpotatoes
and
tomatoes
Deficiency
isuncommonin
adults.In
infants:dermatitis,abdominal
pain,
vomiting,ataxia
andseizures
Pantothenic
acid
Theprecursorto
coenzymeA,an
enzymecritical
totheoxidationand/
orsynthesisofcarbohydratesand
fattyacidsduringmetabolism
.Plays
arole
intheproductionofhorm
ones
andcholesterol
Avariety
offoods,includinggrains,
brassicas,legumes,eggyolk,fish,
yeastandmeat.Alsosynthesised
by
intestinal
bacteria
Veryrare
andhas
beenobserved
only
in
casesofseveremalnutrition
Biotin
Functionsas
acoenzymeforseveral
enzymes
that
catalyse
carboxylation,
decarboxylationanddeamination
reactions(e.g.pyruvatecarboxylase
intheKreb’s
cycle)
forthe
metabolism
ofproteinsand
carbohydrates,andin
theproduction
ofhorm
ones
andcholesterol
Eggyolk,legumes,nuts,potatoes
and
liver.Alsosynthesised
byintestinal
bacteria
Rarely,ifever,occurs
inindividuals
whoconsumearegulardietbut
includes
severedermatitis,loss
of
hair,andlack
ofmuscular
coordination
(Continued)
Table
A5(C
ontinued)
Vitamin
Nature,properties
andfunctions
Main
sources
Deficiency
diseases
Cyanocobalam
in
(vitam
inB12)
Acobalt-containingcoenzymeinvolved
innumerousmetabolicpathways.
Importantformetabolism
andhelps
form
redbloodcellsandmaintain
the
central
nervoussystem
Anim
alproducts:meat,cheese,fish
and
seafood,eggs,kidney,liver,milkand
milkproducts,(essentially
absent
from
plantproducts),microbial
synthesis
Defectin
redbloodcellform
ation
(perniciousanaemia),dim
inished
reflex
responses,mem
ory
impairm
ent,hallucinations,muscle
weakness,problemswithdigestion,
absorptionandmetabolism
of
carbohydratesandfats,im
paired
fertility,growth
anddevelopment
Folicacid
(folate)
Occurs
invariousform
sexpressed
as
pteroglutamic
equivalents.A
coenzymein
thesynthesisofseveral
aminoacids,as
wellas
DNA
purines
andthymine.Required
forenergy
production,protein
metabolism
,
form
ationofredbloodcellsandvital
fornorm
algrowth
anddevelopment
Beans,pulses,meats,organ
meats,bran,
cheese,chicken,dates,dark-green
green
leafyvegetables,milk,oranges,
rootvegetablesfish,whole
grains,
yeast,eggs.Alsosynthesised
by
intestinal
bacteria
Depression,anxiety,fatigue,growth
failure
andanaemia
andbirth
defects
(e.g.spinabifida)
inpregnantwomen
Fat-soluble
vitamins
Vitam
inA(retinol)
Required
forarangeoffunctions,
includingproductionofvision
pigments,resistance
toinfectious
agents,maintenance
ofepithelialcells
insofttissue,mucousmem
branes,
andskin,form
ationandmaintenance
ofhealthyteethandbones.Disease
resultsfrom
both
deficiency
and
excess
Anim
altissues,especiallyfish,liver
and
dairy
products.Transβ-carotenein
green
plantsandyellow
fruitsand
vegetablescanbeconvertedto
vitam
inA
followingingestion
Itchingandburningeyes,eyesties,
nightblindness,blindness,dry
hairor
skin,allergies,loss
ofappetite,loss
ofsm
ell,fatigue,insomnia,im
paired
growth,steroid
synthesisreduction;
decreased
immunesystem
function,
cancersusceptibility
Vitam
inD
(cholecalciferol)
Asteroid
horm
onethat
facilitates
absorptionofcalcium
from
the
intestine,andin
maintainingblood
calcium
homoeostasisandforhealthy
teethandbones.Receptors
are
presentin
mostcellsanditmay
have
manyadditional
effects
Synthesised
intheskin
when
exposedto
UV
light.Alsopresentat
low
concentrationsin
somefoods(fish,
eggs,dairy
products,oatmeal,sw
eet
potatoes),andadded
asergocalciferol
infortifiedfoods(e.g.margarine)
Brittle,softandfragilebones
(osteoporosisandosteopenia)or
teeth,rickets,hypocalcem
ia,poor
metabolism
,diarrhoea,insomnia,
irregularheartbeat,myopia,
nervousness,paleskin,sensitivityto
pain
Vitam
inE
(tocopherol)
Agroupofeightcompounds�
four
tocopherolsandfourtocotrienols,
each
havingadifferentpotency
expressed
asα-tocopherol
equivalents.Functionas
antioxidants,
particularlyto
preventoxidationof
unsaturatedfattyacidsandmaintain
theintegrity
ofcellmem
branes.A
role
inredbloodcellform
ationand
use
ofvitam
inK
Vegetable
oils,herring,whole
grains/
unrefined
cereals,wheatgerm,
oatmeal,darkleafygreen
vegetables,
nuts,eggs,milk,organ
meats,sw
eet
potatoes,soybeans
Enlarged
prostategland,gastrointestinal
disease,hairloss,im
potency
or
sterility,miscarriages,muscular
wasting,orweakness,reduced
circulation,slow
tissuehealing,
increasedsusceptibilityto
cancer,
cardiovasculardisease
andcataracts
Vitam
inK
Necessary
forform
ationofseveral
blood-clottingfactors.Essential
role
inbloodclottingandboneform
ation
Darkgreen
leafyvegetables,soybeans,
eggyolks,liver,oatmeal,rye,and
wheat,majority
synthesised
by
bacteriain
largeintestine
Brittle
orfragilebones
(osteoporosis),
low
bloodplateletcountandpoor
bloodclotting,highbloodglucose
levels
Source:
Adaptedfrom
Bowen,R.,2003.Vitam
ins:introduction.Available
at:,www.vivo.colostate.edu/hbooks/pathphys/misc_topics/vitam
ins.htm
l.(lastaccessed
February2016);McG
ee,W.,
2007.Vitam
ins,Medical
Encyclopedia.Available
at:,www.nlm
.nih.gov/m
edlineplus/ency/article/002399.htm
.(lastaccessed
February2016);Higdon,J.,2004.Pantothenic
Acid.Micronutrient
Inform
ationCentre,
LinusPaulingInstitute.Available
at:,http://lpi.oregonstate.edu/m
ic/vitam
ins/pa/or/biotin.
(lastaccessed
February2016).
Table
A6Properties,functionsandsources
ofminerals
Mineral
Properties
andfunctions
Main
sources
Actionin
foods
Deficiency
diseases
Calcium
Maintainingbloodelectrolyte
balance,structure
and
rigidityofbones
andteeth;
itisinvolved
inblood
clotting,transm
issionof
impulses
from
nerves
to
muscles,regulationofthe
parathyroid
glandand
heartbeat,andfunctioning
ofmuscles,skin,softtissues
andcirculatory,digestive,
enzymatic
andim
mune
system
s.Vitam
inD
is
essential
forcalcium
absorptionandutilisation
Dairy
products,molasses,
nuts,cereals,fruits,tofu,
seafoods,green
leafy
vegetables,seaw
eeds
Texture
modifier:Form
sgels
withnegativelycharged
macromoleculessuch
as
alginates,low-m
ethoxyl
pectins,soyproteins,
caseins,etc.Firmscanned
vegetableswhen
added
to
canningbrine
Eczem
a,fragilebones,heart
palpitations,hypertension,
muscle
cram
ps,
osteomalacia,osteoporosis,
osteopenia,periodontal
disease,rickets,tooth
decay,
slowed
nerveim
pulse
response,decreased
muscle
growth,arthritis
Chromium
Essential
forabsorptionand
metabolism
ofglucose
for
energyproductionand
synthesisofcholesterol,fats
andprotein.Itappears
to
increase
theeffectivenessof
insulinanditsabilityto
regulate
bloodsugar
levels.
Itmay
also
beinvolved
in
protein
synthesis.Correct
functioningofadrenal
glands,brain,blood
circulatory
system
,heart,
immunesystem
,liver
and
whitebloodcells
Fruits,black
pepper,calves’
liver,meat,whole
grains,
maize
andmaize
oil,dairy
products,mushrooms,
potatoes,beer,oysters,
legumes
�Incorrectam
inoacid
metabolism
,increased
serum
cholesterol,myopia,
protein/caloriemalnutrition,
susceptibilityto
infection,
lowered
orescalatedblood
sugar
levels,coronaryartery
disease
Copper
Anumber
ofproteinsand
enzymes
contain
copper,
someofwhichareessential
fortheutilisationofiron.It
isinvolved
inprotein
metabolism
,respiration,
healingprocesses,
maintenance
ofhaircolour,
andform
ationofmyelin
sheathsthat
protect
nerve
fibres,anditisablood
antioxidant.Itcombines
withzincandvitam
inCto
form
elastinandform
ation
ofbones
andredbloodcells
Avocado,barley,cauliflower,
nuts,lamb,oranges,organ
meats,raisins,salm
onand
seafood(oysters),legumes,
green
leafyvegetables,
soybeans
Catalystforlipid
peroxidation,ascorbic
acid
oxidation,nonenzymatic
oxidativebrowning.Colour
modifier:May
cause
black
discolorationin
canned,
curedmeats.Enzyme
cofactorfor
polyphenoloxidase
Elevated
serum
cholesterol,
fracturesandbone
deform
ities,osteoporosis,
impairedrespiration,skin
sores,slowed
healing
processes,poorhairand
skin
colouring,loss
intaste
sensitivity
Texture
stabiliser:Stabilises
egg-w
hitefoam
s
Iodine
Trace
amountsarerequired
for
correctfunctioningof
immunesystem
,brain
and
thyroid
glandwhich
regulatesthebody’s
productionofenergyand
metabolicrate.Itis
involved
inconversionof
caroteneto
vitam
inA,
protein
synthesisand
synthesisofcholesterol
Iodised
salts,seafood,
seaw
eeds,asparagus,fish,
garlic,beans,mushrooms,
sesameseeds,soybeans,
spinach
KIO
3isadoughim
prover,
improves
bakingqualityof
wheatflour
Thyroid
dysfunction,goitre
(enlarged
thyroid)and
hypothyroidism,leadingto
slowed
mentalandphysical
development
Iron
Required
forproductionof
haemoglobin
and
myoglobin,someenzymes,
oxygenationofredblood
cells,healthygrowth
and
resistance
todisease,
Liver,redmeat,darkgreen
leafyvegetables,eggs,
seafood,fish,brewer’s
yeast,dates,legumes,
peaches,pears,pumpkins,
raisins,rice
andwheat
CatalystforFe2
1andFe3
1
andlipid
peroxidationin
foods.Colourmodifier�
colouroffreshmeat
dependsonvalence
ofFein
myoglobin
and
Iron-deficiency
anaemia,
breathingdifficulties,brittle
nails,hairloss,dizziness,
constipation
(Continued)
Table
A6(C
ontinued)
Mineral
Properties
andfunctions
Main
sources
Actionin
foods
Deficiency
diseases
healthyim
munesystem
and
energy
bran,sesameseedsand
soybeans
haemoglobin:Fe2
1isred,
Fe3
1isbrown.Form
s
green,blueorblack
complexes
with
polyphenoliccompounds.
ReactswithS22to
form
black
FeS
incanned
foods.
Enzymecofactor:
Lipoxygenase,
cytochromes,
ribonucleotidereductase
Magnesium
Essential
forenzymeactivity
andprotein
synthesis,assists
incalcium
andpotassium
uptaketo
maintain
blood
electrolyte
balance,
importantrole
inbone
form
ation,carbohydrate
and
mineral
metabolism
,
functioningofarteries,
bones,cells,digestive,
immuneandreproductive
system
s,heart,nerves,and
teeth.Extracellular
magnesium
iscritical
for
maintainingelectrical
potentialsofnerveand
muscle
mem
branes
andfor
Mostfoods,especiallydairy
products,fruits,fish,meat,
seafood,garlic,limabeans,
sesameseeds,tofu,green
leafyvegetables,whole
grains
Colourmodifier�
removal
of
Mgfrom
chlorophyll
changes
colourfrom
green
toolive-brown
Decreased
bloodpressure
and
bodytemperature,coronary
heartdisease,interference
withtransm
issionofnerve
andmuscle
impulses
causes
disorientation,hyperactivity,
noisesensitivity,insomnia,
muscle
weaknessor
trem
ors;disruptionofpH
balance,calcium
depositsin
kidneys,bloodvesselsand
heart,digestivedisorders
andmanyother
symptoms
transm
issionofnerve
impulses
tomuscles.Use
of
diuretics,laxatives,
vomitinganddiarrhoea
can
significantlycontribute
to
magnesium
requirem
ent
Manganese
Anantioxidant,activates
enzymes
andhas
rolesin
protein,carbohydrate
and
fatmetabolism
,bloodsugar
regulation,healthynerves
andim
munesystem
,sex
horm
oneproduction,
skeletal
development
Whole
grains,fruits,
vegetables
Enzymecofactor:pyruvate
carboxylase,superoxide
dismutase
Poorreproductive
perform
ance,growth
retardationandcongenital
malform
ations,abnorm
al
form
ationofboneand
cartilageandim
paired
glucose
tolerance
Molybdenum
Essential
forseveral
metabolic
enzymes
foroxidationof
fatsandmetabolism
of
calcium,magnesium,copper
andnitrogen.Itmay
also
be
anantioxidant
Plantfoods
�Im
pairedreproductionand
weightgain,increasedrate
ofheartbeatandbreathing,
visual
problemsand
shortened
life
expectancy
Nickel
Activatorforsomeenzymes
andinvolved
inhorm
one
andlipid
metabolism
and
cellmem
braneintegrity
Plantfoods
Catalystforhydrogenationof
vegetable
oils�
finely
divided,elem
entalNiis
mostwidelyusedforthis
process
Reducedgrowth,im
paired
liver
function,changes
in
skin
colourand
reproductiveproblems
Phosphorus
Abalance
ofmagnesium,
calcium
andphosphorusis
required
fortheseminerals
tobeusedeffectively.
Essential
componentof
boneandto
utilise
vitam
ins
tometabolise
foodand
Mostfoods,especially
asparagus,maize,dairy
products,eggs,fish,fruits,
garlic,sunflower
seeds,
meats,wheatbranand
whole
grains
Acidulent�
H3PO4in
soft
drinks.Leaveningacid
�Ca(HPO4) 2isafast-acting
leaveningacid.Moisture
retentionin
meats�
sodium
tripolyphosphate
improves
moisture
retention
Boneloss,weakness,anorexia.
Highlevelsofphosphorus
caninhibitcalcium
uptake
andmay
resultin
osteoporosis,arthritis,
pyorrhoea,ricketsandtooth
(Continued)
Table
A6(C
ontinued)
Mineral
Properties
andfunctions
Main
sources
Actionin
foods
Deficiency
diseases
maintain
electrolyte
balance,correctfunctioning
ofbrain
cells,circulatory
anddigestivesystem
s,eyes,
liver,muscles,nerves
and
teeth/bones
incuredmeats.
Emulsificationaid�
phosphates
areusedto
aid
emulsificationin
comminutedmeatsandin
processed
cheeses.
Stabiliser
inevaporated
milk
decay.Nervousdisorders,
heartandkidney
problems
Potassium
Importantin
abalance
with
sodium
forcellular
metabolism
andregulating
transfer
ofnutrientsto
cells,
maintainingbloodpressure
andelectrolyte
balance,
transm
ittingelectrochem
ical
impulses.Correct
functioningofblood,
endocrine/digestiveand
nervoussystem
s,heart,
kidneys,musclesandskin.
Use
ofdiuretics,laxatives,
vomitinganddiarrhoea
can
significantlycontribute
to
potassium
requirem
ent
Dairy
products,fish,fruit,
meat,poultry,vegetables,
whole
grains,beans,nuts,
potatoes,wheatbranand
yam
s
KClmay
beusedas
asalt
substitute,butmay
cause
bitterflavour.Leavening
agent�
potassium
acid
tartrate
Interference
withtransm
ission
ofnerveandmuscle
impulses,heartpalpitations
andarrhythmias,heart
attack,stroke.Decreased
bloodpressure,salt
retention,oedem
a,increased
cholesterol,muscle
weakness,respiratory
distress,weakreflexes
Selenium
Anantioxidantthat
protectsall
mem
branes,reducescancer
risk,enhancesim
mune
system
andprotectsagainst
heartdisease.Required
with
vitam
inEforproductionof
antibodies,bindingoftoxic
metals,am
inoacid
metabolism
andpromotion
ofgrowth
andfertility.
Productionof
prostaglandinswhichaffect
bloodpressure
andplatelet
aggregation
Seafoods,organ
meats,
cereals(dependingon
levelsin
soils)
Enzymecofactorfor
glutathioneperoxidase
Premature
aging,heartattack,
musculardystrophy,cystic
fibrosis,infertilityand
increasedrisk
ofcancer
Keshan
disease
(endem
ic
cardiomyopathyin
China)
was
associated
with
selenium
deficiency
Sodium
Withpotassium
for
maintainingcellularwater
balance
andblood
electrolyte
balance/pH
and
needed
forstomach,
lymphatic
system
,nerveand
muscle
function.Excessive
saltincreasesbloodpressure
Virtually
allfoods,especially
celery,eggs,meat,dairy
products,miso,poultry,
processed
foods,salt,
seafoodandseaw
eeds
Flavourmodifier�
NaC
l
elicitstheclassicsaltytaste
infoods.Preservative�
NaC
lmay
beusedto
lower
water
activityin
foods.
Leaveningagents�
many
leavingagentsaresodium
salts,e.g.sodium
bicarbonate,sodium
aluminium
sulphate,
sodium
acid
pyrophosphate
Cramps,decreased
resistance
toinfection,muscle
shrinkageorweakness,low
bloodsugar
levels,
dehydration,heart
palpitationsandheart
attack,arthritis,rheumatism,
neuralgia,shortattention
span
andmentalconfusion
Sulphur
Essential
forresistingbacterial
infection,aidsoxidation
reactions,stim
ulatesbile
secretionsin
theliver
and
protectsagainsttoxic
substances.Required
for
correctfunctioningofskin,
immunesystem
,blood,liver
Brusselssprouts,beans,
cabbage,eggs,garlic,fish,
meatsandonions
Browninginhibitor�
sulphur
dioxideandsulphites
inhibitboth
enzymatic
and
nonenzymatic
browning
Poorresistance
tobacterial
infections
Usedin
dried
fruits.
Antimicrobial�
prevents/
controlsmicrobialgrowth.
Widelyusedin
wine
making
(Continued)
Table
A6(C
ontinued)
Mineral
Properties
andfunctions
Main
sources
Actionin
foods
Deficiency
diseases
Zinc
Needed
tomaintain
required
functioningofim
mune
system
,thymusandspleen,
maintainingconcentrations
ofvitam
inEin
theblood,
correctfunctioningof
blood,bones,eyes,heart,
joints,liver
andprostate
gland.A
componentof
insulinandmanyenzymes,
includingthose
involved
in
metabolism
ofphosphorus,
proteinsandalcohol.Levels
canbedecreased
by
diarrhoea,kidney
disease,
cirrhosisoftheliver,
diabetes
Fish,meats,seafood,whole
grains,liver,eggyolks,
beans,mushrooms,nuts,
pumpkin
seeds,sardines,
soybeans,wheatgerm
ZnO
isusedin
theliningof
cansforprotein-richfoods
tolessen
form
ationofblack
FeS
duringheating.Zncan
beadded
togreen
beansto
helpstabilisethecolour
duringcanning
Poormem
ory,decreased
learningability,delayed
sexual
maturity,sterility,
growth
retardationand
dwarfism
,loss
oftasteand
smell,poorcirculation,
susceptibilityto
infections
andprolonged
wound
healing,retarded
growth,
prostateandim
munesystem
disorders,liver
dam
age
Source:
Adaptedfrom
Romito,K.,O’Brien,R.,2014.Minerals:TheirFunctionsandSources
Guide.WebMD.Available
at:,www.webmd.com/vitam
ins-and-supplements/tc/minerals-their-
functions-and-sources-credits.
(,www.webmd.com.
.search
‘minerals-their-functions-and-sources’)(lastaccessed
February2016);Miller,D.R.,1996.Minerals.In:Fennem
a,O.R.(Ed.),
FoodChem
istry.MarcelDekker,New
York,pp.617�6
50;Anon,2011.Functionsandfoodsources
ofsomecommonminerals.DieticiansofCanada.
Available
at:,www.dietitians.ca/Your-
Health/Nutrition-A
-Z/M
inerals/Functions-and-Food-Sources-of-Common-M
inerals.aspx.
(,www.dietitians.ca.
.select
‘YourHealth’.
‘NutritionA-Z’.
‘Minerals’)(lastaccessed
February
2016).
Table
A7Examplesoffunctionalcomponents
offoods
Component
Source
Potentialbenefit
Carotenoids
Beta-carotene
Carrots,variousfruits
Neutralises
free
radicalswhichmay
dam
agecells;bolsters
cellularantioxidant
defences
Lutein,zeaxanthin
Kale,spinach,maize,
eggs,citrusfruits
May
contribute
tomaintenance
ofhealthyvision
Lycopene
Tomatoes,processed
tomatoproducts
Role
incancerrisk
reductionincludingbreast,digestivetract,cervix,bladder,
skin
andpossibly
lung
Dietary
(functionalandtotal)fibre
Insoluble
fibre
Wheatbran
May
contribute
tomaintenance
ofahealthydigestivetract
Beta-glucan
Oat
bran,rolled
oats,oat
flour
Cholesterol-lowering,canreduce
totalandlow-density
lipoprotein
(LDL)
cholesterol,therebyreducingtherisk
ofcoronaryheartdisease
(CHD)
Soluble
fibre
Psyllium
seed
husk
May
reduce
risk
ofCHD
Whole
grains
Cerealgrains
May
reduce
risk
ofCHD
andcancer;may
contribute
tomaintenance
ofhealthy
bloodglucose
levels
Fattyacids
Monounsaturatedfattyacids
Treenuts
May
reduce
risk
ofCHD
byalteringbloodcholesterollevels
Polyunsaturatedfattyacids
(PUFAs)
�omega-3fattyacids
�ALA
Walnuts,flax
May
contribute
tomaintenance
ofmentalandvisual
function
PUFAs�
Omega-3fattyacids
�DHA/EPA
Salmon,tuna,marineand
other
fish
oils
Can
lower
triglyceridefatsin
theblood.May
reduce
risk
ofCHD,may
contribute
tomaintenance
ofmentalandvisual
function
Thecardioprotectiveeffect
offish
consumptionobserved
insomeinvestigations,
butnotin
others.n23fattyacidslower
triglyceridelevelsbutincrease
LDL
cholesterol
(Continued)
Table
A7(C
ontinued)
Component
Source
Potentialbenefit
PUFAs�
conjugated
linoleic
acid
(CLA)
Beefandlamb;some
cheeses,flaxseed
oil
May
contribute
tomaintenance
ofdesirable
bodycompositionandhealthy
immunefunction.Anticarcinogenic.CLA
increasesin
processed
foods
(significantbecause
manymutagensandcarcinogenshavebeenidentified
in
cooked
meats).Effectivein
suppressingtumours
inmice,may
beunique
mechanism(s)bywhichCLA
modulatestumourdevelopment
Flavonoids
Anthocyanidins
Berries,cherries,red
grapes
Bolsters
cellularantioxidantdefences;may
contribute
tomaintenance
ofbrain
function
Flavanols
Tea,cocoa,chocolate,
apples,grapes
May
contribute
tomaintenance
ofhearthealth.Cancerchem
opreventiveeffects
inanim
alsbutinconclusiveepidem
iological
studies.Benefitsmay
berestricted
tohighintakes
inhigh-riskpopulations.May
also
reduce
risk
ofCVD
butnot
yet
conclusive
Catechins,epicatechins,
procyanidins
Flavanones
Citrusfruits
Neutralisefree
radicalsthat
may
dam
agecells;bolstercellularantioxidant
defences.Protectiveagainstavariety
ofcancers.Evidence
accumulatingof
cancerpreventativeeffect
oflimonene�
suggestedas
agoodcandidatefor
human
chem
oprevention.A
metabolite
oflimonene,perrillylalcohol,
undergoingphaseIclinical
trialsin
patientswithadvancedmalignancies
Flavonols
Onions,apples,tea,
broccoli
Neutralisefree
radicalswhichmay
dam
agecells;bolstercellularantioxidant
defences
Proanthocyanidins
Cranberries,cocoa,apples,
strawberries,grapes,
wine,peanuts,
cinnam
on
Inhibitadherence
ofE.colito
uroepithelialcells.Contribute
tomaintenance
of
urinarytracthealthandhearthealth
Isothiocyanates
Sulphoraphane
Cruciferousvegetables:
cauliflower,broccoli,
cabbage,kale,
horseradish
Decreased
cancerrisk.May
enhance
detoxificationofundesirable
compounds
andbolstercellularantioxidantdefences.Enzymemyrosinasecatalyses
glucosinolatesto
isothiocyanates
andindoles.Indole-3
carbinolisbeing
studiedforcancerchem
opreventiveproperties,particularlythemam
mary
gland.Sulforaphaneisan
isothiocyanatein
broccoli
Phenols
Red
wine
Growingevidence
that
phenoliccontentin
redwinecanreduce
risk
ofCVD.
PhenolicsubstancespreventoxidationofLDLin
theprocess
ofatherogenesis.
Alcohol-free
wineshownto
increase
totalplasm
aantioxidantcapacity.Grape
juiceiseffectivein
inhibitingtheoxidationofLDL.Red
winealso
asourceof
trans-resveratrol,shownto
haveoestrogenic
properties
whichmay
explain
cardiovascularbenefits,andalso
shownto
inhibitcarcinogenesisin
vivo
Caffeic
acid,ferulicacid
Apples,pears,citrusfruits,
somevegetables
May
bolstercellularantioxidantdefences;may
contribute
tomaintenance
of
healthyvisionandhearthealth
Plantstanols/sterols
Freestanols/sterols
Maize,soy,wheat,wood
oils,fortifiedfoodsand
beverages
May
reduce
risk
ofCHD
Stanol/sterolesters
Fortifiedtable
spreads,
stanolesterdietary
supplements
Blocksabsorptionfrom
thegutofcholesterolin
bileandcholesterolingestedin
food.Can
lower
totalcholesterolandLDLcholesterollevels,raisingornot
changingHDL-cholesterolin
thebloodandhavingnoreported
sideeffects.
May
reduce
risk
ofCHD
Polyols
Sugar
alcohols�
xylitol,sorbitol,
mannitol,lactitol
Somechew
inggumsand
other
foodapplications
May
reduce
risk
ofdentalcaries
(Continued)
Table
A7(C
ontinued)
Component
Source
Potentialbenefit
Prebiotics
Inulin,fructo-oligosaccharides,
polydextrose
Whole
grains,onions,
somefruits,garlic,
honey,leeks,fortified
foodsandbeverages
May
improvegastrointestinal
health;may
improvecalcium
absorption
Probiotics
Lactobacilli,bifidobacteria
Yoghurt,other
dairy
and
nondairy
applications
May
improvegastrointestinal
healthandsystem
icim
munity
Phytoestrogens
Isoflavones
Soybeansandsoy-based
foods
May
reduce
risk
ofCHD
butexactmechanism
ofhypocholesterolemic
effect
not
fullyelucidated.Thoughtto
playpreventiveandtherapeuticrolesin
CVD,
cancers
ofthebreast,prostateandbowel,osteoporosis,andthealleviationof
menopausalsymptoms.Because
isoflavones
areweakestrogens,they
may
act
asantiestrogenscompetingwithendogenousestrogensforbindingto
oestrogen
receptor.Thismay
explain
whypopulationsthat
consumesignificantam
ounts
ofsoyhavereducedrisk
ofoestrogen-dependentcancerbutepidem
iological
resultsareinconsistent.Nopublished
clinical
trialsontherole
ofsoyin
reducingcancerrisk
Daidzein,Genistein
Lignans�
enterodioland
enterolactone,form
edin
intestinal
tractbybacterial
actiononplantlignan
precursors
Flaxseed,rye,some
vegetables
May
contribute
tomaintenance
ofhealthheartandhealthyim
munefunction
Enterodiolandenterolactonesimilar
toestrogensandpossessweakly
oestrogenic
andantiestrogenic
activitiesandmay
playarole
inpreventionofoestrogen-
dependentcancers,butnoepidem
iological
dataandrelativelyfew
anim
al
studiesto
supportthishypothesis
Soyprotein
Soyprotein
Soybeansandsoy-based
foods
May
helpreduce
risk
ofCHD
Sulphides/thiols
Diallylsulphide,allylmethyl
trisulphide
Garlic,onions,leeks
Cancerchem
opreventive,antibioticandcholesterol-loweringproperties.May
enhance
detoxificationofundesirable
compounds;may
contribute
to
maintenance
ofhealthyim
munefunction.Cardioprotectiveeffectsmay
bedue
tocholesterol-loweringeffect
butgarliccomponentresponsible
isunclear.
Aminoacid,alliin,isconvertedbyallinaseinto
allicinwhichdecomposesto
form
numeroussulphur-containingcompounds,someofwhichmay
have
chem
opreventiveactivity.Inconclusiveresultsmay
bedueto
variationin
organosulphurcompoundsin
garlicproducts.Allium
vegetablesmay
have
protectiveeffect
againstgastrointestinal
tractcancers.Garlicadvocatedfor
preventionofCVD,possibly
throughantihypertensiveproperties
but
insufficientevidence
torecommenditas
aroutineclinical
therapy
Dithiolthiones
Cruciferousvegetables
Contribute
tomaintenance
ofhealthyim
munefunction
CHD,coronaryheartdisease;CVD,cardiovasculardisease;HDL,high-density
lipoproteins;LDL,low-density
lipoproteins.
Source:
Adaptedfrom:IFIC,2006.Functional
Foods.International
FoodInform
ationCouncil.Available
at:,www.foodinsight.org/Background_on_Functional_Foods.
(lastaccessed
February
2016);Arvanitoyannis,I.S.,van
Houwelingen-K
oukaliaroglou,M.,2005.Functional
foods:asurvey
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385�4
04;Ascherio,A.,Rim
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intakeofmarinen23fattyacids,fish
intake,andtherisk
ofcoronarydisease
amongmen.
N.Engl.J.Med.332,977�9
82;Clinton,S.K.,1998.Lycopene:
chem
istry,biologyandim
plicationsforhuman
healthanddisease,Nutr.Rev.56(2),35�5
1;Frankel,E.N.,Kanner,J.,German,J.
B.,Parks,E.,Kinsella,J.E.,1993.Inhibitionofoxidationofhuman
low-density
lipoprotein
byphenolicsubstancesin
redwine.Lancet341,454�4
57;Gould,M.N.,1997.Cancer
chem
opreventionandtherapybymonoterpenes.Environ.HealthPerspect.105,977�9
79;Hasler,C.M
.,1998.Functional
foods:theirrole
indisease
preventionandhealthpromotion,Institute
of
FoodTechnologistsExpertPanel
onFoodSafetyandNutrition.FoodTechnol.52(2),57�6
2;Jang,M.,Cai,J.,Udeani,G.,Slowing,K.V.,Thomas,C.F.,Beecher,C.W
.W.et
al.,1997.Cancer
chem
opreventiveactivityofresveratrol,anaturalproduct
derived
from
grapes.Science
275,218�2
20;Katiyar,S.K.,Mukhtar,H.,1996.Tea
inchem
opreventionofcancer:epidem
iologic
and
experim
entalstudies(review).Int.J.Oncol.8(2),221�2
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eier,L.,Weerings,K.G.C.,Steck,S.,Kok,F.J.,1997.Tea
andcancerprevention�
anevaluationoftheepidem
iologic
literature.Nutr.Cancer27(1),1�1
3;Law
son,L.D.,Wang,Z.-Y.J.,Hughes,B.G.,1991.IdentificationandHPLCquantitationofthesulphides
anddialk(en)ylthiosulfinates
incommercial
garlic
products.Planta
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okingandlungcancer.Proc.Am.Assoc.CancerRes.38,113(abstract
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Messina,M.,Barnes,S.,Setchell,K.D.R.,1997.Phytooestrogensandbreastcancer.Lancet350,971�9
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juiceonurinaryandnonurinarybacterial
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e31Annex A: Food components