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Food Science 210 > Proteins > Flashcards

Proteins Flashcards

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1
Q

what is the most important role of protein in food?

A

acts as an emulsifier

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2
Q

what are plant sources of protein?

A

pulses (more) and cereal grains (less)

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3
Q

what is the dimer of cysteine called?

A

cystine (dimerize under oxidizing conditions)

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4
Q

food source with highest protein?

A

meat, fish

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5
Q

what is an example of a basic amino acid important in food science?

A

Lysine

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6
Q

what is an example of a polar, uncharged amino acid important in food science?

A

cysteine

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7
Q

Milk protein rich in ____ tend to brown more quickly because of the _____ reaction

A

lysine; Maillard Browning

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8
Q

What are the essential amino acids?

A

histidine, leucine, isoleusine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

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9
Q

in acidic pH, the AA has a ___ charge; in basic pH, the AA has ____ charge

A

positive; negative

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10
Q

what is a zwitterion?

A

a neutral AA (when pH = pI)

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11
Q

the pH at which the charge on AA becomes neutral

A

isoelectric point

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12
Q

Why is the isoelectric point important in food?

A

at this point, protein can’t stay in solution so will form aggregates and precipitate out

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13
Q

what is casein’s isoelectric point?

A

pH 4.5-4.6

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14
Q

how is yogurt formed?

A

action of lactobacillus or addition of lemon juice brings the pH to pI

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15
Q

casein derived phosphorylated peptides that enhance vit D absorption?

A

caseinophosphopeptides

3 Ser, 2 Glu

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16
Q

34 AA residues, with antimicrobial properties that is produced during certain bacterial fermentation

A

Nisin

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17
Q

Aspartame is about _____sweeter than sucrose; it is made up of ___ and aspartate

A

200 times; phenylalanine, methanol

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18
Q

sucralose is ___ times sweeter than sucrose, and is made through selective ___ which makes a product we can’t digest

A

600; chlorination

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19
Q

what is the primary driving force behind tertiary structure formation?

A

thermodynamic stability in aqueous solution

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20
Q

what interactions stabilize protein structure?

A

H bond, electrostatic, disulide, and especially hydrophobic

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21
Q

what are the three types of tertiary structure?

A

globular (insoluble AA), disordered (interact well with water), fibrous (strong secondary structure)

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22
Q

an example of globular protein

A

whey

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23
Q

an example of disordered protein

A

casein

24
Q

example of fibrous protein

A

muscle protein collagen

25
Q

examples of proteins that show quartenary structure

A

hemoglobin (2 alpha, 2 beta) and casein (2 alpha, 1 beta, 1 kappa)

26
Q

diseases that are due to protein misfolding?

A

BSE, Alzheimers, Parkinsons, cancers

27
Q

How do you calculate True Protein Digestibility %?

A

(nitrogen intake - fecal nitrogen) / nitrogen intake , x 100

28
Q

How do you calculate PER? (protein efficiency ratio)

A

gain in body weight / quantity protein consumed, x 100

29
Q

how do you get PDCAAS?

A

mg limiting a.a. in 1g test protein / mg same amino acid in 1g reference protein x % TPD

30
Q

what is the limiting amino acid?

A

a.a with lowest ratio relative to established amino acid requirement values for humans 2-5 yrs old

31
Q

what does PDCAAS stand for?

A

Protein digestibility corrected a.a. score

32
Q

__ protein is the only complete non-animal source of complete protein

A

soy

33
Q

which amino acid is missing in beef?

A

tryptophan

34
Q

wheat, rice and corn lack __

A

lysine

35
Q

legumes lack ____

A

methionine

36
Q

the enzyme that reacts with lipid

A

lipase

37
Q

Enzyme found commonly in plants and animals, requiring Cu and O2 to function; catalyzes the oxidation of wide range of phenolic compounds

A

polyphenoloxidase (PPO)

38
Q

PPO is responsible for ________; spontaneously occurring in cut fruits and veggies

A

enzymatic browning

39
Q

what is the purpose of polyphenol activity?

A

as a plant defense mechanism designed to turn plant phenols into antimicrobial products in case of tissue injury

40
Q

what are some ways to prevent enzymatic browning?

A

blanching (denature enzyme), remove O2, addition of antioxidants, inhibit enzyme by lowering pH, SO2 to stop formation of melanins

41
Q

what are some ways that protein can be denatured?

A

heat, change pH, change solvent polarity, addition reactive comps, presence of interfaces

42
Q

what are effects of protein denaturation?

A

loss of solubility and bio activity, gelation, conversion of globular–>fibrous structure, surface active properties

43
Q

unfolding of hydrophobic portion of a protein chain in presence of ____ interface is called _____ properties

A

oil/water; surface active

44
Q

___ enzyme, found in cow’s stomach, is involved in cheese making

A

Rennet

45
Q

A fibrous protein derived from collagen; heat with acid/alkali to denature, cooling to ___degrees causes the coils to regain triple helical structure as a gel

A

gelatin; 25

46
Q

gel melting is observed at around ___degrees

A

37

47
Q

how are sausages produced?

A

a meat emulsion is heated to 75 degrees, making cross links and 3D gel with entrapped water and fat globs

48
Q

Examples of generating protein foam

A

-whipping egg white–>meringue (more air bubbles means stiffer peaks)

49
Q

what is surface activity?

A

tendency move to surface (air/water) or interface (oil/water)

50
Q

how does a molecule become surface active?

A

must have hydrophilic and hydrophobic groups

51
Q

How does surface denaturation occur?

A

addition of oil in a protein-water system causes the protein to unfold to move hydrophobic parts into oil phase

52
Q

casein unfolds to a ________ configuration; whey maintains a ___ structure

A

loop-tail-train; globular

53
Q

arrange these flours in increasing protein content: cake, whole wheat, gluten, all purpose, bread

A

cake, all purpose, bread, whole wheat, gluten

54
Q

What is the process of gluten formation?

A

mix and knead gliadin and glutenin to crosslink via disulfide bonds

55
Q

glutenin fraction determines ____ while gliadin fraction determines ___

A

elasticity; fluidity and stickiness

56
Q

pulses contain ____ proteins that inhibit ___ when consumed raw

A

antinutritional; digestion

57
Q

examples of antinutritional proteins?

A

lectins (cancer prevention); protease enzyme inhibitors

Food Science 210 (23 decks)

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