Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Food Chemistry 2 > Food enzymes > Flashcards

Food enzymes Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Gourmet Food flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Apoenzyme?
Holoenzyme?
Prosthetic group?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How to make high fructose corn syrup? why?

A
  • hydrolyzing corn start into glucose in solution –> glucose converted into fructose
  • fructose = sweeter than glucose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

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

A
  1. lyase
  2. isomerase
  3. oxidoreductase
  4. translocase
  5. transferase
  6. hydrolase
  7. ligase
  8. lyase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

6 beneficial effects of enzymes

A
  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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do enzymes facilitate reactions?

A

by reducing the energy barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the 4 undesirable effects of enzymes?

A
  1. undesirable texture changes
  2. undesirable color changes
  3. undesirable flavor changes
  4. production of harmful compounds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the chemical reaction of proteases?

A

hydrolyze proteins in different ways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

exoproteases (4) vs endoproteases (2)

A

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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

2 major carbohydrates found in foods + characteristics

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

breakdown of TG reaction

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

hydrolytic vs oxidative rancidity

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A
  1. desired
  2. undesired
  3. undesired
  4. desired
  5. undesired
  6. desired
  7. desired
  8. desired
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name 7 oxidoreductases

A
  1. ascorbic acid oxidase
  2. polyphenol oxidase
  3. glucose oxidase
  4. catalase
  5. lipoxygenase (lipoxidase)
  6. xanthine oxidase
  7. peroxidase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A
  • 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
17
Q

how to make fuel alcohol?

A

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

18
Q

which enzymes used in non-alcoholic beverages/juices?

A

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

19
Q

which 4 enzymes used in baking?

A
  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
20
Q

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

A
  • papain in papaya to tenderize meat, resistant to heat
  • proteases (must be heat stable) –> tenderazition + solubilization)
21
Q

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

A

transglutaminases

22
Q

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 ______

A
  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
23
Q

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

A

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
-

24
Q

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

A
  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
25
Q

3 traditional methods to control enzymatic reactions? + examples

A
  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)
26
Q

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

A
  • 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
27
Q

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

A
  • 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
28
Q

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

A

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)

29
Q

5 novel methods for controlling enzymatic reactions in food:

A
  1. high pressure treatment (ultra high pressure processing)
  2. Enzyme treatment (killer enzyme)
  3. Enzyme inhibitors
  4. Chemical modifications
  5. Ionizing reactions
30
Q

Explain how high pressure treatment can control enzymatic reactions

A

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

31
Q

Explain how enzyme treatments can control enzymatic reactions

A

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

32
Q

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

A
  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
33
Q

Name the 7 enzyme groups

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

Food Chemistry 2 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions