Selected non-nutrients: Week 6 Flashcards
what does a non-nutrient mean
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
give examples of a non-nutrient
- FIBRE
- CHOLINE: (important for making phospholipids)
- PHYTOCHEMICALS: a range of compounds some of which have been associated with health.
give examples of selected non-nutrients
-Phenols
-Polyphenols
-Sulphur containing compound
-Alkaloids(e.g caffeine)
what are some examples of polyphenols in food
-FLAVONOLS: Apple, broccoli, onions
-FLAVONES: celery, bell peppers, lemons
-ANTHOCYANIDINS: Raspberries, strawberries, grapes, wine
-ISOFLAVONES: Soya sauce, milk, tofu
What roles may Polyphenols have in terms of human health
-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
what are the 3 classifications of proteins & explain what there composed off
- Simple proteins: only amino acids
*Conjugated proteins: amino acids + prosthetic group - Derived proteins: modified by chemical or enzymatic treatment
give examples of simple proteins
*Albumins & Globulins: globular& soluble(egg)
*Collagen: linear, fibrous & insoluble(connective tissue in meat)
*Gluten: Gliadin if globular & Glutenin is fibrous (both in cereal)
give examples of conjugated proteins and explain them
-Lipoproteins: LDL, HDL(in egg yolk)
-Glycoproteins: in egg white & soya
-Metalloproteins: haemoglobin, myoglobin in meat
give examples of derived proteins and explain them
- chemical modification: soya proteins
-Enzymatic modification: milk proteins
what are the structural properties of proteins
-FORMATION OF GELS
-STABILISE EMULSION& FOAMS
-FORM FILMS
how does gelation(formation of gels) occur
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
what are the interfacial properties of stabilise emulsion & foams
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
give examples of oil-in-water emulsion
mayonnaise, sauces, mustard
give examples of both oil & foam emulsion
ice cream- not just an emulsion as instead of oil being the hydrophobic bit, air is instead
what are films that are formed by proteins
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)
what is the purpose of edible films
-barrier to moisture & carbon dioxide- enhances shelf life & appearance
-biodegradable packaging
-improve mechanical handling proteins
give the name and the functional properties of enzymes in the Oxidoreductase class
-Glucose oxidase: dough strengthening
-Lipoxygenase: dough strengthening, dough whitening
give the name and the functional properties of enzymes in the Transferase class
-Transglutaminase: modification of viscoelastic properties
-Fructosyltransferase: Synthesis of fructose oligomers
give the name and the functional properties of enzymes in the Hydrolase class
-Amylase: Starch liquefaction & saccharification
-Lactase- Lactose Hydrolysis
give the name and the functional properties of an enzymes in the Isomerase class
Xylose(glucose) isomerase: glucose isomerization to fructose
give the name and the functional properties of an enzymes in the Layse class
Acetolactate decarboxylase: beer maturation
what are the 5 examples of enzymes used in food processing
1) Isomerase
2) Invertase
3) Lipoxygenase
4) Protease
5) Lactase
what does the enzyme isomerase do in food processing
D glucose—> D-fructose
fructose is sweeter than glucose- can uses it at higher conc tan glucose to make it ‘healthier’
what does the enzyme Invertase do in food processing
sucrose +H2O–> alpha-D glucose + beta-D glucose
produces sugars for confectionary(sweets) as they are more stable & less likely to crystallise
what does the enzyme Lipoxygenase do in food processing
unsaturated fatty acids—> fatty acid hydroperoxides
causes fat rancidity as it could cause oxidation but can improve dough and flavour of bread
what does the enzyme Protease do in food processing
Used for meat tenderisation (can be injected in the animal before its killed to start the process), flavouring, Unami tastes
what does the enzyme Lactase do in food processing
lactose—> Galactose + Glucose
lactase is added in milk
what are the CHEMICAL PROPERTIES/reactions of within proteins: Involved in (un)desirable reactions
- Reactions of the carboxyl group
-Reactions of Amino Group
-Reactions with Thiol Groups
-Other reactions between amino acids
how is reaction of the carboxyl group involved in (un)desirable reactions
usually negative- specific in fish & microorganisms
-Decarboxylation of histidine into histamine: scombroid food poising
how is reaction of the Amino group involved in (un)desirable reactions
-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..
how is reaction with Thiol groups involved in (un)desirable reactions
formation of disulphide bonds- increases extensibility & elasticity of dough provides more acceptable texture of meat batters
how is other reactions between amino acids involved in (un)desirable reactions
-Discolouration in low acid, high protein content- produced in canned meat as they reacting with the tin or iron
