Topic 5: Part F

Question 1

Functions of proteins in foods

Answer 1

• absorb and bind water (sausage, cake)
• thicken and increase viscosity (soups, gelatin)
• emulsify fats (salad dressing)
• bind flavour (simulated meats)
• production of foams (whipped topping)
• dough formation

Question 2

Non enzymic browning reactions

Answer 2

• caramelization

- maillard reaction

Question 3

Caramelization

Answer 3

series of chemical reactions occur when sugars are heated to temps great than their melting point (200C).

Question 4

Caramelization begins with..

Answer 4

dehydration and ends with polymerization that yields brown colours

Question 5

When caramelization reactions aren’t too extensive than a..

Answer 5

desirable caramel flavour and light brown colour results

Question 6

When caramelization reactions too extensive then a ..

Answer 6

dark bitter coloured compounds are formed

Question 7

Caramel is widely used in food industry fro..

Answer 7

flavour and colour properties

Question 8

Caramel consists of…

Answer 8

• 50% digestible CHO
• 25% non digestible CHO
• 25% polycyclic aromatice hydrocarbons

Question 9

Maillard reaction

Answer 9

reaction between the carbonyl group (CO) of carbohydrate and amine group (NH2) of an amino acid or protein at high temp

Question 10

In maillard reaction a series of reactions such as..

Answer 10

fragmentation and polymerization eventually lead to formation of brown pigments (melanoidins)

Question 11

Final flavour and color in a mallard reaction is dependent on..

Answer 11

compounds involved, conditions of temp, pH moisture, etc under which the reaction occurs

Question 12

When can maillard reaction be desirable

Answer 12

in baking and roasting

Question 13

When can maillard reaction be undesirable

Answer 13

browning and off-flavour development of skim milk powder stored over a long period of time.

Question 14

Proteins as enzymes

Answer 14

act as catalyst that speed up chemical reaction without being used in reaction itself

Question 15

Enzymes do not stop functioning when ..

Answer 15

animal is slaughtered or when a plant is harvested therefore we must consider enzyme activity when dealing with foods

Question 16

Names of enzymes often include ..

Answer 16

the substrate or substance on which they act and have an “ase” ending (lactase, protease)

Question 17

The name of an enzyme may also describe the ..

Answer 17

reaction that is catalyzed (oxidase; catalyzes oxidation reactions)

Question 18

Enzymes are used in foods such as..

Answer 18

meat tenderizers (bromelain from pineapple, papain from papaya, actinidain from kiwi, pinaple, mango, pinapple, papaya), clotting of milk (rennin/chymosin).

Question 19

Enzymatic browning is an ..

Answer 19

undesirable browning reaction that occurs when some fruits and veggies (banana, apple, potato) are cut and exposed to oxygen **bad

Question 20

The most common enzyme responsible for browning is called..

Answer 20

polyphenol oxidase

Question 21

The browning reaction can be blocked by ..

Answer 21

denaturing the enzyme using heat or by excluding oxygen by covering the surface of the food or by adding ascorbic acid (vit C)

Question 22

Denaturation involved ..

Answer 22

unfolding a protein structure without breakage of peptide bonds.

Question 23

Most cases denatured proteins are ..

Answer 23

less soluble and an enzyme will lost its functional ability

Question 24

Denaturation is caused by..

Answer 24

cooking, freezing, changes in pH, salts and mechanical action

Question 25

Continuous denaturation (unfolding) can lead to..

Answer 25

recombination of the protein molecules in different ways to produce a new molecular shape.

Question 26

The newly shaped molecules may ..

Answer 26

bond together to form a continuous network referred o as coagulation