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FABS 323 > part 4 > Flashcards

part 4 Flashcards

1
Q

what are antioxidants used for?

A

preservation of food by stopping deterioration, rancidity, discolouration due to oxidation

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2
Q

what is oxidation?

A

electron removal/abstraction from comp by ROS

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3
Q

examples of ROS?

A

hydrogen peroxide, hydroxyl radical, alkoxy, superoxide

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4
Q

why oxidation prob?

A

off flavour and colour, loss of flavour/aroma, discolouration, texture chage, decrease nutr. value, toxic byproducts

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5
Q

why decrease in nutr value by oxidation>

A

essential fatty acid and vitamin destruction

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6
Q

fatty acids in nature are present in form of :

A

triacylglycerols

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7
Q

common unsaturated fatty acids in foods

A

oleic, linoleic (omega 6), linolenic (omega 3)

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8
Q

system we use instead of trans and cis?

A

E and Z

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9
Q

why do unsaturated oxidize?

A

contain allylic hydrogens which are sensitive to abstraction by reactive O species–>autoxidation rxn

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10
Q

which is more stable, conjugated or nonconjugated?

A

conjugated

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11
Q

E=__, Z=___

A

trans;cis

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12
Q

what are the 2 types antioxidants?

A

phenolic comps, organic acids and their salts/esters

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13
Q

ex. of organic acids?

A

ascorbic/citric acid

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14
Q

how do citric acid work?

A

chelate and bind metals (metals take triplet state O to single state)

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15
Q

examples of synthetic phenolic antioxidants?

A

BHA, BHT (no longer GRAS), PG, TBHQ (approved)

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16
Q

BHT is produced through this mech:

A

catalytic alkylation of p-cresol with isobutylene

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17
Q

phys properties of synth phenolic antiox?

A

white/off-white solids with high purity, may react with metals to produce off-colours, poor water sol (except PG), tasteless odourless

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18
Q

why poor water sol good for synth phenolic antiox?

A

so it can protect lipophilic substances

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19
Q

mech of antioxidant?

A

gives up H and e-, generate resonance structures that make hard for oxidation to happen, produce free radical way less reactive than original

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20
Q

food uses of synth phenolics?

A

permitted lvls wt:wt, alone or in combo, based on lipid content–cereal, baking, edible oils, candy, margarine, packaging

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21
Q

what is carry through?

A

the ability of antiox to survive processing steps and impart stability to finshed product

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22
Q

why BHA/BHT good carry through?

A

most sterically hindered

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23
Q

antiox improves:

A

shelf life

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24
Q

toxicity of synth phenolics?

A

potential carcinogen (but in rats forestomach, low validity study); Netherlands cohort study show no association with stomach cancer

25
Q

industrial uses of BHT:

A

food, pet food, pharma and cosmetics, fuel additive, plastics, rubber

26
Q

main mechanism for detox w/ synth phenolic antiox?

A

phase 1: oxidation (enzyme mediated, cytochrome P-450), becomes more water sol. (gallic acid)
phase 2: methylation (go from meta, less water sol, steric hindrance, to ortho conjugates of hydroxyl grp)
phase 3: conjugation (enzyme mediated), make much more water sol.

27
Q

natural phenolic antiox include:

A

tocopherols (racemic D and L), sesamol, gossypol, quercitin, avenanthramides, rosmaridiphenol, ferulic acid, resveratrol, rutin

28
Q

phys properties of tocopherols?

A

pale-yellow viscous oils, readily destroy by heat and UV, easily oxidized by nitrate and metal ions

29
Q

tocopherols antioxidant activity highest in ____ and owest in ___

A

delta; alpha

30
Q

why alpha less active?

A

cuz it is most stericallly hindered

31
Q

possible carcinogen, GI/liver toxicity, antifungal found in sesame seed oil

A

sesamol

32
Q

found to be toxic in non ruminants (reduce O2 availability), natural in cottonseeds, insecticide, male contraceptive

A

gossypol

33
Q

first edible oil produced commercially, number one in WW2?

A

cottonseed oil

34
Q

naturally in fruits and veg, tea leaves, with only half free radical scavenging ability of BHA/BHT

A

quercitin (flavonoid)

35
Q

found in oats

A

avenanthramides

36
Q

what form of avenanthramide is for asthma?

A

tranilast (no phenolics/hydroxyl)

37
Q

naturally occuring phenolic in flax seed

A

ferulic acid

38
Q

found in brown skin of peanut and in red wine:

A

resveratrol

39
Q

found in buckwheat

A

rutin

40
Q

other synth phenolics?

A

Ionox 100, THBP

41
Q

organic acids and salts/esters are ___ soluble

A

water

42
Q

product of citric acid/ascorbic acid?

A

dehydroascorbic acid (quenched the radical!)

43
Q

most reactive radical?

A

hydroxyl

44
Q

why add saturated fats to organic acids?

A

so don’t react with ROS

45
Q

organic acid esters have ___ effect when used with phenolic antiox

A

synergestic; get rid of ALL free radicals!

46
Q

max. addition lvls of organic acid esters depends on:

A

lipid content

47
Q

organic acid esters sold as ____, aids in stabilizing ____

A

natural health product, veg oil

48
Q

sources of free radicals?

A

internal and external

49
Q

ex. of human diseases and free radicals?

A

organ damage, arterial wall lesions, CHD plaque formation, retina damage, DNA breakage, a.a oxidation, membrane damage, joint damage, resp distress, alzheimers, asthma, diabetes, arthritis, parkinson’s

50
Q

what are some cellular protection mechanisms?

A

enzymes like SOD, catalase, peroxidase; glutathione

51
Q

examples of chemopreventive agents?

A

BHA, BHT, PG, TBHQ

52
Q

what are anthocyanins found in?

A

berries!

53
Q

anthocyanins break down into:

A

PGA, PCA

54
Q

anthocyanins are ___ soluble, but CHO can be removed

A

water

55
Q

produced from eggs, fish, rice/corn/soy, potato, etc:

A

antioxidant peptides

56
Q

how antiox peptides work (mechanism)?

A

free radical scavenging (like BHT) and chelation (like citric acid)

57
Q

how does antioxidant peptides incorporate rational design?

A

5-16 a.a., hydrophobic (Leu/Val), random coil, Tyr/Phe/His/pro for H/e- donation

58
Q

antioxidant peptides have ___ structure

A

phenol

FABS 323 (14 decks)

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