Antioxidants. Oxidation of food Oxidation reactions can occur when food is exposed to oxygen in the...
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![Page 1: Antioxidants. Oxidation of food Oxidation reactions can occur when food is exposed to oxygen in the air. Foods containing fats or oils are at the greatest.](https://reader035.fdocuments.us/reader035/viewer/2022062417/5515e88e550346dd6f8b5059/html5/thumbnails/1.jpg)
Antioxidants
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Oxidation of food
Oxidation reactions can occur when food is exposed to oxygen in the air.
Foods containing fats or oils are at the greatest risk of oxidation.
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Foods rich in fats and oils
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When fats react with oxygen they are broken down, causing:
deterioration of flavour (rancidity)
loss of colour
loss of nutritional value
a health risk from toxic oxidation products.
Effects of oxidation on food
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Fat breaking down
Oxygen
FatFat
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Fat molecules
Fat
CH2
CH2
CH2
CH2
CH2
COO
CH2
CH3
CHH
H
CH2
CH2
CH2
CH2
CH
COO
CHCH3
C
C
O
H
H
CH2
CH2
CH2
CH2
CH2
CO
CH2
CH3
R CH2CH2CH2CH CH CH3
Radicals attack near the double bond(NB ‘R’ represents the remainder of the fat molecule)
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Antioxidants
Antioxidants are chemicals that are added to food to prevent the food from ‘going off’.
An antioxidant is a substance that slows down or prevents the oxidation of another chemical.
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Oxidative damage
Oxidation reactions can produce free radicals.
A free radical is a highly reactive species containing an unpaired electron.
Free radicals can damage food by removal of an electron.
Antioxidant molecules ‘mop up’ free radicals to protect the foodstuff.
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Damaging free radical
Electrontransferred
Antioxidant Antioxidant converted to a stable free radical
Neutralised free radical
Radical now in a stable pair
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How does an antioxidant cancel out a free radical?
The antioxidant molecule donates an electron to the potentially damaging free radical.
A stable electron pair is formed, stabilising the free radical.
The antioxidant itself becomes oxidised (loses an electron).
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Types of antioxidants
Antioxidant Natural/synthetic E number Types of food
Vitamin C
(ascorbic acid)
Natural E300 Fruits, jams, vegetables
Vitamin E
(tocopherols)
Natural E306 Oils, meat pies, soya beans
Butylated hydroxyanisole
(BHA)
Synthetic E320 Margarine, cheese, crisps
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Antioxidants in action
Oxidation occurs when the apple is left exposed to air
The apple is protected when dipped in orange juice containing the antioxidant vitamin C
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Vitamin C (ascorbic acid)
The antioxidant vitamin C can act as a reducing agent (electron donor), preventing oxidation (electron loss) from the foodstuff.
C6H8O6 C6H6O6 + 2H+ + 2e-
Ascorbic acid Dehydroascorbic acid