Selected non-nutrients: Week 6

Question 1

what does a non-nutrient mean

Answer 1

a substance that may occur in the diet that may affect our health even though they are not nutrients, plants contain thousands of non-nutrient substances, some of which may be toxic

Question 2

give examples of a non-nutrient

Answer 2

• FIBRE
• CHOLINE: (important for making phospholipids)
• PHYTOCHEMICALS: a range of compounds some of which have been associated with health.

Question 3

give examples of selected non-nutrients

Answer 3

-Phenols
-Polyphenols
-Sulphur containing compound
-Alkaloids(e.g caffeine)

Question 4

what are some examples of polyphenols in food

Answer 4

-FLAVONOLS: Apple, broccoli, onions
-FLAVONES: celery, bell peppers, lemons
-ANTHOCYANIDINS: Raspberries, strawberries, grapes, wine
-ISOFLAVONES: Soya sauce, milk, tofu

Question 5

What roles may Polyphenols have in terms of human health

Answer 5

-polyphenols are generally represented as glycosides in the diet
- some flavonoid glycosides can interact with transporters in duodenum where they are absorbed
- Non-interacting glycoside (rutinoside) pass to colon where bacterial glycosidases degrade them- some absorption may occur

Question 6

what are the 3 classifications of proteins & explain what there composed off

Answer 6

• Simple proteins: only amino acids
  *Conjugated proteins: amino acids + prosthetic group
• Derived proteins: modified by chemical or enzymatic treatment

Question 7

give examples of simple proteins

Answer 7

*Albumins & Globulins: globular& soluble(egg)
*Collagen: linear, fibrous & insoluble(connective tissue in meat)
*Gluten: Gliadin if globular & Glutenin is fibrous (both in cereal)

Question 8

give examples of conjugated proteins and explain them

Answer 8

-Lipoproteins: LDL, HDL(in egg yolk)
-Glycoproteins: in egg white & soya
-Metalloproteins: haemoglobin, myoglobin in meat

Question 9

give examples of derived proteins and explain them

Answer 9

• chemical modification: soya proteins
  -Enzymatic modification: milk proteins

Question 10

what are the structural properties of proteins

Answer 10

-FORMATION OF GELS
-STABILISE EMULSION& FOAMS
-FORM FILMS

Question 11

how does gelation(formation of gels) occur

Answer 11

globular proteins unfold on heating- the denatured chains aggregate to form thermally irreversible gels
Fibrous proteins are able to form thermally reversible gels: gelatine from collagen

Question 12

what are the interfacial properties of stabilise emulsion & foams

Answer 12

proteins from milk and eggs are commonly used to stabilise oil-in-water emulsions & foams.
- they are able to absorb the oil-water & air-water interfaces, preventing aggregation
-small enough to diffuse to the interface at fast rates
- their interface activity will be a function of their: molecular size, amino acid composition, PH, structure and solvent composition

Question 13

give examples of oil-in-water emulsion

Answer 13

mayonnaise, sauces, mustard

Question 14

give examples of both oil & foam emulsion

Answer 14

ice cream- not just an emulsion as instead of oil being the hydrophobic bit, air is instead

Question 15

what are films that are formed by proteins

Answer 15

Application of proteins such as gelatine, whey, soy, corn and wheat gluten as
edible films (refer as edible coatings when applied to fruit and vegetables)

Question 16

what is the purpose of edible films

Answer 16

-barrier to moisture & carbon dioxide- enhances shelf life & appearance
-biodegradable packaging
-improve mechanical handling proteins

Question 17

give the name and the functional properties of enzymes in the Oxidoreductase class

Answer 17

-Glucose oxidase: dough strengthening
-Lipoxygenase: dough strengthening, dough whitening

Question 18

give the name and the functional properties of enzymes in the Transferase class

Answer 18

-Transglutaminase: modification of viscoelastic properties
-Fructosyltransferase: Synthesis of fructose oligomers

Question 19

give the name and the functional properties of enzymes in the Hydrolase class

Answer 19

-Amylase: Starch liquefaction & saccharification
-Lactase- Lactose Hydrolysis

Question 20

give the name and the functional properties of an enzymes in the Isomerase class

Answer 20

Xylose(glucose) isomerase: glucose isomerization to fructose

Question 21

give the name and the functional properties of an enzymes in the Layse class

Answer 21

Acetolactate decarboxylase: beer maturation

Question 22

what are the 5 examples of enzymes used in food processing

Answer 22

1) Isomerase
2) Invertase
3) Lipoxygenase
4) Protease
5) Lactase

Question 23

what does the enzyme isomerase do in food processing

Answer 23

D glucose—> D-fructose
fructose is sweeter than glucose- can uses it at higher conc tan glucose to make it ‘healthier’

Question 24

what does the enzyme Invertase do in food processing

Answer 24

sucrose +H2O–> alpha-D glucose + beta-D glucose
produces sugars for confectionary(sweets) as they are more stable & less likely to crystallise

Question 25

what does the enzyme Lipoxygenase do in food processing

Answer 25

unsaturated fatty acids—> fatty acid hydroperoxides
causes fat rancidity as it could cause oxidation but can improve dough and flavour of bread

Question 26

what does the enzyme Protease do in food processing

Answer 26

Used for meat tenderisation (can be injected in the animal before its killed to start the process), flavouring, Unami tastes

Question 27

what does the enzyme Lactase do in food processing

Answer 27

lactose—> Galactose + Glucose
lactase is added in milk

Question 28

what are the CHEMICAL PROPERTIES/reactions of within proteins: Involved in (un)desirable reactions

Answer 28

• Reactions of the carboxyl group
  -Reactions of Amino Group
  -Reactions with Thiol Groups
  -Other reactions between amino acids

Question 29

how is reaction of the carboxyl group involved in (un)desirable reactions

Answer 29

usually negative- specific in fish & microorganisms
-Decarboxylation of histidine into histamine: scombroid food poising

Question 30

how is reaction of the Amino group involved in (un)desirable reactions

Answer 30

-Acetylation with acetic anhydride increase solubility of protein isolates to be used as ingredients for emulsion
- Formation of Nitrosamines when nitrates are added in meat-gives a desirable flavour & protection against spoilage bacteria
-Maillard Browning: reaction of amino group with the carboxyl group of sugars- gives desirable colour & flavour of bread crust, toast, roasted meats..

Question 31

how is reaction with Thiol groups involved in (un)desirable reactions

Answer 31

formation of disulphide bonds- increases extensibility & elasticity of dough provides more acceptable texture of meat batters

Question 32

how is other reactions between amino acids involved in (un)desirable reactions

Answer 32

-Discolouration in low acid, high protein content- produced in canned meat as they reacting with the tin or iron