Enzymes

Question 1

why are enzymes important in the food industry?

Answer 1

they are naturally present and we may want to inactivate them or insure that they do act. they can be used as indicators of proper processing or to create other desirable compounds

Question 2

enzyme functionality depends on

Answer 2

a.a. sequence, folding of polypeptides, interactions of a.a. side chains by electrostatic and hydrophobic forces and disulfide bridges, assemblage with protein subunits

Question 3

the nature of the enzyme is dependent on

Answer 3

the identity of the a.a. that set up the active site

Question 4

what is the main function of enzymes?

Answer 4

to decrease activation energy and through that catalyze (accelerate) a process that would have occured normally but at a much slower rate

Question 5

what environmental properties can affect enzyme activity?

Answer 5

pH, water activity, temperature

Question 6

changes in pH may affect the enzymatic reactions by changing

Answer 6

enzyme activity, enzyme stability, interaction and change in reaction equilibrium

Question 7

most enzymes exhibit optima near what pH

Answer 7

neutral (7)

Question 8

why is water activity important for enzymes?

Answer 8

it serves as a co-substrate in enzymes activity

Question 9

how can water activity be changed to affect enzymes?

Answer 9

dehydration and freezing are used to preserve foods by the removal or immobilization of water. altered enzyme activity.

Question 10

what enzymes can be used to test for proper heat treatment?

Answer 10

alkaline phosphatase activity can be used to see if dairy has been pasteurized - peroxidase can be used to insure the adequate blanching of vegetables

Question 11

what are beneficial advantages of using enzymes over conventional chemical catalysts?

Answer 11

active in low concentrations - high specificity, can ex differentiate between stereoisomers - low reactivity with other substances - more environmentally friendly - can work under mild temp, pressure and pH conditions preserving integrity of heat-labile essential nutrients - activity can be stopped ex by drying or heat treatment

Question 12

what are potential undesirable effects of enzymes in food?

Answer 12

autolytic changes such as proteolysis in cheese or canned tuna, may cause off flavouring - proteases lipases and carbohydrases break down biological molecules which may impact quality negatively - decarboxylases and deaminases degrade biomolecules like free a.a. to form undesirable and/or toxic components - polyphenol oxidases and lipoxygenases promote oxidations and undesirable discolorations and/or color loss in fresh vegetables and fruits - ascorbic acid oxidase destroys vit C

Question 13

milk enzymes can come from several sources, which?

Answer 13

native milk, somatic cells present in milk, airborne bacterial contamination, intentionally added bacteria

Question 14

lipases like lipoprotein lipase can cause defects in milk, explain

Answer 14

associates with casein micelle but when milk is agitated enzyme comes into contact with fat and degrades fat to produce off flavours

Question 15

what function does plasmin serve in cheese maturation?

Answer 15

it breaks down proteins

Question 16

how can alkaline phosphatase be used as an indicator of pasteurization completeness?

Answer 16

if it shows activity, temperatures have not been high enough to pasteurize the milk

Question 17

catalase activity in milk indicates

Answer 17

elevated leukocyte levels, characteristic for mastitis milk

Question 18

why is lactase sometimes added to milk in processing?

Answer 18

for lactose removal to increase sweetness, prevent crystallization in ice cream or reduce lactose levels for intolerant

Question 19

what can transglutaminase be used for?

Answer 19

cross-linking of protein molecules to improve texture in meat/seafood products or to give better texture to structured meat products.

Question 20

what endogenous grape enzymes are very important in wine making?

Answer 20

pectolytic enzymes which hydrolyzes pectin chains into small fragments. reduces viscosity and allows sedimentation of clouding particles, and is thus beneficial for faster and more complete juice clarification and easier wine filtration.

Question 21

why are proteases important in wine making?

Answer 21

degrade proteins forming haze and degrade enzymes forming C6 alcohols that could give grassy taste

Question 22

why do we want to inactivate polyphenol oxidases in wine making?

Answer 22

they oxidate phenolic compounds and cause loss of color and formation of brown color. the enzyme can be removed by clarification (sedimentation or centrifugation) or inactivated by heat treatment and/or sulfur dioxide addition

Question 23

why are amylases important in breadmaking?

Answer 23

they break down starch into smaller sugars, making it easier for yeast to act. also improves taste, crust color and toasting qualities of the bread