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Flashcards in Food Antioxidants Deck (38)
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1

What are antioxidants?

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

2

What are Free Radicals?

Uncharged molecules or ions with unpaired electrons

3

What is Auto-oxidation

Spontaneous oxidation of molecules caused by atmosphere O2

4

What are the two types of rancidity?

Oxidative and Hydrolytic

5

What are the differences between oxidative and hydrolytic rancidity

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

6

What is rancidity accelrated by?

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

7

Total antioxidant capacity (TAC)

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

8

Oxygen radical absorbance capacity (ORAC)

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

9

Total Radical Antioxidant Potential (TRAP)

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

10

What are some examples of reactice species?

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

11

What are some agents that promote oxidation?

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

12

Name the three mechanism of oxidation

Initial step
Propagation step
Termiantion step

13

Explain the Initial Step

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

14

Explain the Propagation Step

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

15

Explain the termination Step

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

16

What is an alternative initiation?

ROO-H --> RO* + *OH
2ROO-H --> RO* + ROO* + H2O

17

Oxidation with metal ion

M + ROO-H --> RO* + OH- + M+
M+ + ROO-H --> ROO* + H+ + M+

18

What are the types of antioxidants? Differences?

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

Preventive antioxidants are what?

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

20

Non-free radical deactivators

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

What are the Non-radical oxygen species

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

22

What are the Radical oxygen species?

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

23

What reaction oes Catalase catalyze?

2 H2O2 --> 2 H2O + O2

24

What reaction does Glutathione Peroxidase catalyze?

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

25

What reaction does Superoxide dismutase SOD catalyze?

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

26

What are the Natural Antioxidants?

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

27

Where are Vitamin E,C, 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

Examples of Polyphenolic acids

Catechins, caffeinic acid, vanillin acid
Found in food products such as red wine, tea, thymem oregano

29

Examples of Flavonoids

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

30

What are the artifical antioxidants?

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