Food enzymes

Question 1

Apoenzyme?
Holoenzyme?
Prosthetic group?

Answer 1

Apoenzyme:
- protein part of the enzyme
- for some enzymes, only apoenzyme is suffifient for functional activity (ie trypsin, pepsin, chymotrypsin)
Holoenzyme:
- when apoenzyme works together with a cofactor (usually in form of metal ion: Cu, Zn, Mg, Mn) to have a functional activity
Prosthetic group:
- essential non-protein part of the enzyme

Question 2

How to make high fructose corn syrup? why?

Answer 2

• hydrolyzing corn start into glucose in solution –> glucose converted into fructose
• fructose = sweeter than glucose

Question 3

Which type of enzymes are these?
1. histidine decarboxylase
2. glucose isomerase
3. polyphenol oxidase
4. ADP/ATP translocase
5. transglutaminase
6. lipases
7. fatty acyl synthase
8. aldolase

Answer 3

1. lyase
2. isomerase
3. oxidoreductase
4. translocase
5. transferase
6. hydrolase
7. ligase
8. lyase

Question 4

6 beneficial effects of enzymes

Answer 4

1. perceived as natural and non-toxic (bc derived from living organisms) = preferred by most consumers (vs chemicals)
2. generally more specific than chemicals –> produce consistent results from batch to batch
3. require in small quantities to form desired products
4. effective under mild reaction conditions of temp and pH –> preserves nutrients in foods + nees less expansive containers (vs high acid/alkaline substrates)
5. ability to recover and reuse enzyme = decrease cost (enzymes can be immobilized into stationary support material)
6. use mild heat treatment to inactivate enzyme after desired transformation

Question 5

How do enzymes facilitate reactions?

Answer 5

by reducing the energy barrier

Question 6

what are the 4 undesirable effects of enzymes?

Answer 6

1. undesirable texture changes
2. undesirable color changes
3. undesirable flavor changes
4. production of harmful compounds

Question 7

what is the chemical reaction of proteases?

Answer 7

hydrolyze proteins in different ways

Question 8

exoproteases (4) vs endoproteases (2)

Answer 8

EXO:
- remove aa from terminal ends from proteins
- carboxypeptidase = act on C terminal
- amino peptidase = act on N terminal
- useful to reduce bitterness in food products (that is caused by hydrophobic aa at termini)
ENDO:
- breakdown peptide bonds randomly within protein molecule –> forms low MW
- pronounced texture change if extensive proteolysis (solubiliization/solvation)

Question 9

Why is cellulose more resistant to hydrolysis compared with starch? (2)

Answer 9

• cellulose doesn’t have branches –> only linear = can pack more compactly + more crystalline –> enzymes don’t easily have access to glycosidic bonds
• need to pretreat cellulose with heat to destroy crystaline structure

Question 10

2 major carbohydrates found in foods + characteristics

Answer 10

Starch
- amylose (linear) + amylopectin (branched)
- a 1,4 and a 1,6
- broken down by amylases
Cellulose:
- b 1,4 –> humans cannot digest
- broken down by cellulase

Question 11

breakdown of TG reaction

Answer 11

TG + H2O –> glycerol + FFA
- catalyzed by lipases or lipolytic enzymes

Question 12

hydrolytic vs oxidative rancidity

Answer 12

• hydrolytic –> caused by FFA formed by lipase reaction
• oxidative –> caused by oxidation: unsat FFA may oxidize to form various carbonyl compounds in rxn catalyzed by lipoxygenase = rancid flavors
  *rancidity mostly undesired but can be desired in some cheeses and chocolate

Question 13

lipolysis desired or undesired?
1. soups
2. dairy
3. meat
4. buttermilk
5. fish
6. baked goods
7. chocolate
8. coffee whiteners

Answer 13

1. desired
2. undesired
3. undesired
4. desired
5. undesired
6. desired
7. desired
8. desired

Question 14

Name 7 oxidoreductases

Answer 14

1. ascorbic acid oxidase
2. polyphenol oxidase
3. glucose oxidase
4. catalase
5. lipoxygenase (lipoxidase)
6. xanthine oxidase
7. peroxidase

Question 15

Which enzymes (4 ish) needed in cheese making?
- what do they do?

Answer 15

• rennin or rennet, pepsins or chymosins
• cuts off bond between carb part and protein part of kappa-casein –> para-k-casein binds to Ca2+ ions and precipitates = curding –> rippens into cheese
• remaining of liquid = whey proteins

Question 16

which 2 enzymes needed in winemaking and brewing?
- how?

Answer 16

• proteases and amylases
• starchy material hydrolyzed into fermentable sugars bc of various amylase mixture
• fermentable sugars (glucose, maltose) are converted to ethanol via enzymes of glycolytic pathway
• ethanol distilled to make stronger alcohol

Question 17

how to make fuel alcohol?

Answer 17

same steps as to make drinkable alcohol except use cellulosic material as starting material (convert to fermentable sugar, then ethanol)

Question 18

which enzymes used in non-alcoholic beverages/juices?

Answer 18

various amylases and pectinases
- break down pectin –> used to enhance sweetness of beverages OR remove sediments (pectin) to clarify beverage (less cloudy)

Question 19

which 4 enzymes used in baking?

Answer 19

1. amylases: breakdown carb to form fermentable sugars (more sweet) + fermentable sugars can coproduce CO2 to cause load expansion
2. proteases: breakdown proteins + modify gluten for good texture + peptides formed contribute to flavor
3. lipases to breakdown margarine/fat source
4. lipoxidases: bleach flour for white breads

Question 20

which 2 enzymes used in meat industry?
- for what?

Answer 20

• papain in papaya to tenderize meat, resistant to heat
• proteases (must be heat stable) –> tenderazition + solubilization)

Question 21

which enzyme to form larger chunks of meat (chicken nuggets and surimi)?

Answer 21

transglutaminases

Question 22

7 industrial applications of proteases
1. removal of ____________
2. modification of _____ and _____ proteins for incorporation into ________ products
3. hydrolysis of ________ _______ for use as flavorants
4. modification of ________ and ________
5. ________ beverages
6. __________
7. recovery of ______ protein from offal, ______ and ______

Answer 22

1. bitterness caused by hydrophobic aa on terminal ends –> use exopeptidases to remove
2. milk and whey proteins –> dietetic products
3. wheat gluten
4. collagen and gelatin: gelatin = made from collagen found in animal tissue
5. alcoholic bevs
6. baking
7. scrap protein from blood and bones

Question 23

collagen and gelatin
- found where?
- roles?
- water soluble?

Answer 23

COLLAGEN
- found in animal tissue
- serves a structural role + holds integrity of body
- not water soluble
GELATIN:
- made from collagen: heat collagen to denature + make it amenable to proteolysis –> use pepsin/trypsin/chymotrypsin to breakdown collagen into gelatin
- used as thickener
- can absorb and thicken
-

Question 24

other applications of enzymes:
1. dextranases
2. tannases
3. keratinase
4. synthesis of protein-like molecules

Answer 24

1. remove dental plaque
2. solubilization of cold tea solids (so they stay in solution at low temp)
3. elimination of hair –> breaks down keratin
4. reverse of hydrolysis: decrease moisture by increasing aa –> enzymes will bring aa together to form gel-like protein + also used to incorporate essential aa (lysine) to foods

Question 25

3 traditional methods to control enzymatic reactions? + examples

Answer 25

1. based on temp (blanching, freezing, chilling, pasteurization) 2. based on water activity (salting, dehydration) 3. based on chemicals (sulfites & nitrites, acids, alkalis, antioxidants, chelating agents)

Question 26

explain how controlling temp can control enzymatic reactions - high vs low temp

Answer 26

- high temp disrupts bonds between and within proteins --> lose conformation --> denature --> lose activity - low temp --> reactions are slow bc molecules are sluggish --> less efficient interactions btw reactants and enzymes --> enzymes get inactivated

Question 27

explain how water activity can control enzymatic reactions - enzyme shape - 4 steps ish - how to decrease water activity?

Answer 27

- enzymes have globular shape + surrounded by thin film of moisture (that must be present for enzyme to retain conformation and activity) - decrease water activity (by adding salt, sugar and alcohol --> can all bind moisture) = thin film of moisture is stripped off --> enzyme loses globular shape/conformational integrity --> lose activity

Question 28

explain how chemicals can control enzymatic reactions A. nitrites and sulfites B. chelating agents (ex) C. antioxidants

Answer 28

A. nitrites and sulfites act as inhibitors by binding to active sites of enzymes B. chelating agents remove essential cofactors/prosthetic groups from metalloenzymes to cause loss of activity --> ie strip off copper from a metalloenzyme - ex: EDTA and citric acid C. antioxidants take away O2 --> O2 often act as coreactant in certain rxns (ie glucose oxidase)

Question 29

5 novel methods for controlling enzymatic reactions in food:

Answer 29

1. high pressure treatment (ultra high pressure processing) 2. Enzyme treatment (killer enzyme) 3. Enzyme inhibitors 4. Chemical modifications 5. Ionizing reactions

Question 30

Explain how high pressure treatment can control enzymatic reactions

Answer 30

high pressure = shrink volume = disrupts conformational integrity of enzyme/microorgs --> loss of activity

Question 31

Explain how enzyme treatments can control enzymatic reactions

Answer 31

killer enzymes/anti-enzymes --> highly potent, can breakdown native OR undenatured enzymes/proteins - get these killer enzymes from species without functional stomach (ie cunner fish) --> evolved into making their enzymes more powerful to breakdown prots that havent been pretreated with acid

Question 32

explain how these can control enzymatic reactions 1. enzyme inhibitors (explain + example) 2. chemical modifications 3. ionization

Answer 32

1. used to curtail/reduce proteolysis in foods --> used in Alaskan Pollock used for surimi (we don't want it to be too tender) - ex: a-2-macroglobulin, soybean trypsin inhibitor 2. attach chemical (usually fats/lipids) to enzyme --> changes conformation of enzyme and disrupts its integrity --> new complex has less activity = slows down catalysis 3. use of ionizing radiation can cause ionization of groups in enzymes --> alter catalytic properties

Question 33

Name the 7 enzyme groups

Answer 33

1. oxidoreductase 2. transferase 3. hydrolase 4. lyase 5. isomerase 6. ligase 7. translocase