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Food Chemistry - FDSC251 > U9 > Flashcards

U9 Flashcards

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1
Q

true or false: egg white is high in carb and lipid content

A

false! 1%

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2
Q

main 4 protein constituents in albumin

A
  1. ovalbumin
  2. ovotransferrin
  3. ovomucoid
    lysozyme
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3
Q

what kind of protein is ovalbumin

A

phosphoglycoprotein

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4
Q

what is special about ovalbumin that the other egg white proteins dont have

A

free sulfhydryl group

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5
Q

how stable is ovalbumin

A

not very stable - easily coagulated in heat and easily denatures when exposed to new surfaces

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6
Q

what are 2 important functions of ovalbumin

A

stabilizes foam

gelling agent

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7
Q

what kind of gel does ovalbumin create (in heat)

A

transparent, turbid gel

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8
Q

what process is used to purify ovalbumin

A
  1. half-saturate with ammonium sulfate
  2. filter
  3. sulfuric acid lowers the pH to pL 4.6-4.8
  4. recrystallizations
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9
Q

what kind of protein is ovotransferrin

A

iron-binding transferrin

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10
Q

what kind of prosthetic group does ovotransferrin have

A

carbohydrate

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11
Q

what allows ovotransferrin to have bacteriostatic and bactericidal avticities

A

iron-sequestering properties

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12
Q

how to purify ovotransferrin

A
  1. half-saturate with ammonium sulfate
  2. precipitate with more ammonium sulfate or alcohol fractionation
    or ion exchange chromotography
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13
Q

what is the most easily heat-denatured egg protein

A

ovotransferrin

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14
Q

wht kind of protein is ovomucoid

A

glycoprotein

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15
Q

what is the quaternary structure of ovomucoid like

A

3 homogenous domains crosslinked

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16
Q

where are the polysacchridees of the ovomucoid

A

attached to Asp

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17
Q

how are ocomucoids purified

A

complete saturation with ammonium sulfate or adding excess alcohol

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18
Q

what kind of protein is lysozyme

A

bacteriolytic enzyme

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19
Q

what is the function of lysozme

A

Catalyzes hydrolysis of glycosidic links between NAM and NAG in bacterial cell walls

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20
Q

optimal ph activity for lysozyme

A

5.3-6.4

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21
Q

what funcitonal characterisitc is special about lysozyme

A

heat stable and stable during drying

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22
Q

what is avidin

A

basic protein

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23
Q

what is ovoglobulin

A

foaming protein

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24
Q

what is ovoinhibitor

A

inhibits trypsin, chymotrypsin, elastase

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25
Q

what is flavoprotein

A

binds riboflavin

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26
Q

what does yolk act like in food and why

A

lipid - it has high proportions of phosphoplipids and lipoproteins

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27
Q

what function does yolk have

A

emulsifier

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28
Q

4 classes of yolk proteins

A

Lipoproteins - LDL and HDL
lipid-free globular proteins
phosphoproteins
minor proteins

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29
Q

what is heat coagulation

A

thermal denaturation and aggregation of proteins in albumen and yolk

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30
Q

what is denaturation

A

breaking of h-bonds, uncoiling of peptide chains, exposure of reactive groups

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31
Q

what do proteins form when denatured and with what bonds

A

aggregate to form a 3D gel network via h-binds, electrostatic links, disulfide links

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32
Q

what effect does heating albumin have

A

increased viscosity and opacity

33
Q

what effect does heating have on yolk

A

viscosity increases (65C) and solidifies (70C)

34
Q

how does increasing temperature and heating time affect gel

A

strengthens it

35
Q

what does the oH of the gel depend on

A

net charge of the protein

36
Q

describe the gel at its isoelectric point

A

protein aggregates into a curd, forming an opaque gel

37
Q

describe the gel at basic pH

A

protein denatures, forming a translucent, rubbery gel

38
Q

describe the gel at acidic pH

A

poor winding capacity, forming a coarse, open gel structure

39
Q

describe the gel at pH 9

A

lots of crosslinking, forming a firm gel with high WBC

40
Q

how does dry heating affect the egg protein’s propertie

A

improves foaming, gelling, and emulsifying properties

41
Q

how is dry heating performed

A

storing the dried egg white at 80C with controlled humidity for 7-10 days, forming a partially denatured structure

42
Q

how does conjugating a protein with a polysaccharide effect the proteins properties

A

favors protein-protein interactions, so it protects the protein from thermal denaturaion and increases amphiphilic properties

43
Q

how do enzymes work

A

they bind with high specificity and lower the activation, speeding up chemical reactions

44
Q

what are oxidoreductases

A

catalyze oxidations or reductions of substrates

45
Q

what does lipoxygenase do

A

lipid oxidation - adding O to a fatty acid

46
Q

what does polyphenol oxidase do

A

enzymatic browning - oxidizes phenols in food

47
Q

what do hydrolases do

A

catalyzes hydrolysis of substrates using water

48
Q

what do proteases do

A

cleave the peptide bonds in proteins, affecting texture and protein modification

49
Q

what do amylases do

A

cleave glycosidic bonds in carbohydrates, affecting texture and carbohydrate modification

50
Q

wht do lipases do

A

cleave ester bonds, affecting hydrolytic rancidity and fat crystallization modification

51
Q

what do isomerases do

A

catalyze intramolecular rearrangements

52
Q

what does glucose isomerase do

A

convert aldose to ketose (glucose to fructose)

53
Q

what do glycoside hydrolases do

A

hydrolyze glycosidic bonds in stach

54
Q

a-amylase

A

hydrolyze alpha 1-4 link within starch. Releasing dextrins, maltose, and maltotriose

55
Q

b-amylase

A

hydrolyze beta 1-4 links from the non-reducing end of starch. Releasing maltose

56
Q

glucoamylase

A

hydrolyzes alpha 1-4 and alpha 1-6 links in starch. Can go all the way to glucose

57
Q

pullulunase

A

hydrolyzes alpha 1-6

58
Q

where are glycoside hydrolases supplied from

A

microbes or food systems

59
Q

what 3 processes are glycosde hydrolysases used in

A

production of corn syrup, baking, and brewing

60
Q

what occurs in corn syrup production

A
  1. a-amylase breaks down amylose into amylopectin
  2. glycoamylase breaks it down into glucose OR b-amylase / pullulanase break down into maltose - depending on what is desired
61
Q

what occurs in baking

A
  1. a-amylases dextrinize dirsupted starch granules
  2. b-amylase hydrolyze dextrins into maltose
  3. the fermentable sugar maltose is used by yeast amd causes produciton of CO2
  4. the bread rises
62
Q

what occurs in brewing

A

amylases in barley malt hydrolyze starch to form maltose during mashing which is then used by yeast o produce CO2 and ethanol

63
Q

what kind of enzyme is invertase

A

glycoside hydrolase

64
Q

what does invertase do

A

hydrolyzes glycosidic bond in sucrose, resulting in an invert sugar - fructose and glucse

65
Q

what kind of enzyme is lactase

A

glycoside hydrolase

66
Q

what does lactase do

A

hydrolyzes glycosidic bond in lactose

67
Q

what effect does lactase have on products

A

less crystallization , sweeter, and lactose-free

68
Q

what kind of enzyme are pectinases

A

hydrolase

69
Q

what do pectinases do

A

hydrolyze the methyl ester link in pectin

70
Q

what effect do pectinases have on products

A

less cloudy juices

71
Q

what kind of enzyme are proteases

A

hydrolases

72
Q

what do proteases do

A

hydrolye peptide bonds in proteins

73
Q

what is papain

A

protease found in papaya used as a meat tenderizer to break down collagen

74
Q

what are papains used in

A

meat tenderizers, make beer more clear (proteins aggregate to make it cloudy)

75
Q

what are examples of digestive proteases

A

trypsin, chymotrrypsin, pepsin, chymosin, microbial proteases,

76
Q

what kind of enzyme are lipases

A

hydrolases

77
Q

what do lipases do

A

hydrolyze ester bond between FA and glycerol

78
Q

1,3-lipases v 2-lipases

A

1,3: cleaves sn1 and sn2 ester

2: cleaves sn2 ester

Food Chemistry - FDSC251 (10 decks)

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