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Food Chemistry 2 Quiz > Food Antioxidants > Flashcards

Food Antioxidants Flashcards

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1
Q

What are antioxidants?

A

Substances that protect foodstuff from oxidative damage. Act by interacting with highly reactive species such as fre radicals
Convert into less reactive/more stable form

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2
Q

What are Free Radicals?

A

Uncharged molecules or ions with unpaired electrons

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3
Q

What is Auto-oxidation

A

Spontaneous oxidation of molecules caused by atmosphere O2

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4
Q

What are the two types of rancidity?

A

Oxidative and Hydrolytic

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5
Q

What are the differences between oxidative and hydrolytic rancidity

A

Oxidative rancidity = off flavors cuased y byproducts of oxidation
Hydrolytic rancidity= caused by liberation of free fatty acids

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6
Q

What is rancidity accelrated by?

A 
Oxidative= trace metals, salt, light, bacteria, molds
Hydrolytic= water, lipases, phospholipases, bacteria, molds
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7
Q

Total antioxidant capacity (TAC)

A

Full or total antioxidant acitivty against various reactive oxygen/nitrogen species

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8
Q

Oxygen radical absorbance capacity (ORAC)

A

determines the degradation of antioxidant after being mixed with free radical generators such as peroxyl radicals

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9
Q

Total Radical Antioxidant Potential (TRAP)

A

Time required to deplete antioxidants by reactive species produced at gieven rate

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10
Q

What are some examples of reactice species?

A 
Free radicals - superoxide, hydroxyl radicals
Singlet oxygen
Hydrogen peroxide
Peroxynitrite
Hypochlorous acid
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11
Q

What are some agents that promote oxidation?

A 
Molecular oxygen
higher temperature
UV radiation and light exposure
Metal ions
Unsaturated molecules
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12
Q

Name the three mechanism of oxidation

A

Initial step
Propagation step
Termiantion step

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13
Q

Explain the Initial Step

A

Reactive oxygen species reacts with compound and causes the compound to be reactive instead. The reactive species is more stable

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14
Q

Explain the Propagation Step

A

The reactive compound reacts with oxygen and creates a ROO* (peroxyl radical)
The Peroxyl radical can then react with R-H and creates a ROOH and R* , which begins the process again

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15
Q

Explain the termination Step

A

Results in the ending of the free radicals
2RRO–> ROO-R + O2
ROO + R* –> ROO-R
R* + R* –> R-R

ROO* = peroxyl radical
R* = Radical
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16
Q

What is an alternative initiation?

A

ROO-H –> RO* + *OH

2ROO-H –> RO* + ROO* + H2O

17
Q

Oxidation with metal ion

A

M + ROO-H –> RO* + OH- + M+

M+ + ROO-H –> ROO* + H+ + M+

18
Q

What are the types of antioxidants? Differences?

A

Primary Antioxidants - free radical scanvengers like Vit E, Vit C, carotenoids, flavonoids, phenolics

Secondary Antioxidants - non-free radical scavengers
Turn ROOH –> non reactive products –> alkoxy and hydroxy

Secondary are often used in conjunction with primary

19
Q

Preventive antioxidants are what?

A

Metal ion chelators - ferritin, lactoferrin ,amino acid, peptides, protein
Non-radical deecomposition of hydroperoxides and hydrogen peroxide

20
Q

Non-free radical deactivators

A

1) Metal Chelators ( ascorbic acid, citric acid, EDTA)
2) UV radiation absorbers (eg aryl salicycltes, formalmidine, cina tino SORB, phenylpthalisomdes)
3) Conversion of hydroperoxides to non-radical species
4) Deactivation of reactive oxygen species

21
Q

What are the Non-radical oxygen species

A 
Molecular Oxygen (O2)
Hydroperoxides (H2O2)
Peroxynitrite (ONOO)
Singlet Oxygen (1^O2)
Organic Peroxide ROOR'
22
Q

What are the Radical oxygen species?

A 
Superoxide Anion O2*-
Hydroxyl Radical *OH
Nitric Oxide NO*
Peroxyl Radical RO*
 Peroxide O2*2-
Hydroxyl ion OH-
23
Q

What reaction oes Catalase catalyze?

A

2 H2O2 –> 2 H2O + O2

24
Q

What reaction does Glutathione Peroxidase catalyze?

A

2GSH + H2O2 –> GS-SG + 2H2O
GSH represents reduced monomeric glutathione
glutathione reductase then reduces oxidized glutathione to complete cycle NADPH –> NADP

25
Q

What reaction does Superoxide dismutase SOD catalyze?

A

half reaction of SOD (cytoplasm, mitochondria, extracellular. Catalyzes dismutation of superoxide
Mn - SOD+ + O2- –> Mn-SOD + O2

26
Q

What are the Natural Antioxidants?

A 
Vitamin E,C,A
Polyphenolic acids
Flavonoids
Chlorophyll
Carotenoids
Glutathione
Selenium
Co enzyme Q
Melatonin
27
Q

Where are Vitamin E,C, A

A

Anthocyanin pigment - cyanidin, malvidin, delphindin, found in food stuff such as grapes and cranberries
Carotenoids - B carotene, lutein, lycopene, cryptoxanthin, in green leafy , peppers, carrots, mangoes, pumpkin
Vit E- vegetable oils, avocado, nuts, seeds, whole grains
Vit C- organs, black current, kiwi, mangoes, brocoli, spinach

28
Q

Examples of Polyphenolic acids

A

Catechins, caffeinic acid, vanillin acid

Found in food products such as red wine, tea, thymem oregano

29
Q

Examples of Flavonoids

A

tea, green team citrus fruit, red wine, onion, apples, soybean, tofu

30
Q

What are the artifical antioxidants?

A 
Butylated Hydroxy Anisole
Propyl Gallate (PG)
Butylated Hydroxytoluene (BHT)
Tertiary Butyl Hydroquinone (t-bHQ)
31
Q

What is the maximum limit of artifical antioxidants?

A

0.02% in foodstuff

32
Q

Sources of antioxidants in plants

A

oil seeds, nuts, legumes, cereal, fruits, roots and tubers, spices, teas

33
Q

Sources of antioxidants in animal products

A

antioxidant enzymes, peptides, aa, proteins, carotenoids

34
Q

Sources of Microbial antioxidants

A

Carotenoid, anthocyanin, artoventin (penicillium), Mycotrienin

35
Q

Uses of Artifical Antioxidants in food

A

Oils, fat, cracekrs, potato chips, margarine, dry cereals

36
Q

What are antimicrobial agents

A

1) Phenolic antioxidants - BHA, also exhibit antimicrobial activity against several bacteria
2) Flavonoids - also have antimicrobial activity against plant pathogens
3) Tannins (polymers of flavonoids) have neen reported to inhibit growth of Aeromones, Bacillus, Clostridium Botulinum, C. Perfingens, Enterobacter
4) Thus antioxidants are hgihly effective preservatives for foods

37
Q

What stabilizes an antioxidant molecule

A

Conjugated systems- resonance and aromatically has an important contribution to antioxidant stabilization capabilities

38
Q

Consumers becoming more cynical about safety of snthetic compounds for food use- What do they want?

A

more natural
More incorportaiton of herbsm spices, in polyunsaturated oils
Tissue culture products
GMO could be used to enhance production of cmopunds with improved resistnace to oxidation

Food Chemistry 2 Quiz (2 decks)

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