Food Antioxidants Flashcards
(38 cards)
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
What are Free Radicals?
Uncharged molecules or ions with unpaired electrons
What is Auto-oxidation
Spontaneous oxidation of molecules caused by atmosphere O2
What are the two types of rancidity?
Oxidative and Hydrolytic
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
What is rancidity accelrated by?
Oxidative= trace metals, salt, light, bacteria, molds Hydrolytic= water, lipases, phospholipases, bacteria, molds
Total antioxidant capacity (TAC)
Full or total antioxidant acitivty against various reactive oxygen/nitrogen species
Oxygen radical absorbance capacity (ORAC)
determines the degradation of antioxidant after being mixed with free radical generators such as peroxyl radicals
Total Radical Antioxidant Potential (TRAP)
Time required to deplete antioxidants by reactive species produced at gieven rate
What are some examples of reactice species?
Free radicals - superoxide, hydroxyl radicals Singlet oxygen Hydrogen peroxide Peroxynitrite Hypochlorous acid
What are some agents that promote oxidation?
Molecular oxygen higher temperature UV radiation and light exposure Metal ions Unsaturated molecules
Name the three mechanism of oxidation
Initial step
Propagation step
Termiantion step
Explain the Initial Step
Reactive oxygen species reacts with compound and causes the compound to be reactive instead. The reactive species is more stable
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
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
What is an alternative initiation?
ROO-H –> RO* + *OH
2ROO-H –> RO* + ROO* + H2O
Oxidation with metal ion
M + ROO-H –> RO* + OH- + M+
M+ + ROO-H –> ROO* + H+ + M+
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
Preventive antioxidants are what?
Metal ion chelators - ferritin, lactoferrin ,amino acid, peptides, protein
Non-radical deecomposition of hydroperoxides and hydrogen peroxide
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
What are the Non-radical oxygen species
Molecular Oxygen (O2) Hydroperoxides (H2O2) Peroxynitrite (ONOO) Singlet Oxygen (1^O2) Organic Peroxide ROOR'
What are the Radical oxygen species?
Superoxide Anion O2*- Hydroxyl Radical *OH Nitric Oxide NO* Peroxyl Radical RO* Peroxide O2*2- Hydroxyl ion OH-
What reaction oes Catalase catalyze?
2 H2O2 –> 2 H2O + O2
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
