Oxidation and Anti-oxidant Flashcards
Oxidation Overview
Cause of food spoilage that leads to rancidity
Food gets unpleasant flavours, decreased nutritive value and some other compounds formed as potentially toxic
Oxidation Phases
Initiation
Propagation
Termination
Initiation
Free radical reacts wih a fatty acid component of a lipid to form an acyl radical
Lipids at risk of initiation phase
Poly-unsaturated fatty acids are particularly susceptible to oxidation
Hydrogens on carbons next to a double bond are easily removed by a radical
Propagation
Acyl radical is very reactive towards oxygen and react to form a peroxy radical
Peroxy radical is highly reactive towards other unsaturated acyl groups to form hydroperoxide and reforming acyl radical
Repeat
Products of propagation
Aldehyde - rancid flavour
Termination
Two free radicals meet and combine to form a non-radical
Results in cross-linking
Oxidation of Proteins
Free radicals including peroxy radical can also interact with amino acids
Proteins in food containing unsaturated lipids are particularly susceptible to oxidation - oily fish
Sulphur containing amino acids are more susceptble
Prevention/reduction of oxidative damage
Avoid initial formation of free radicals
Prevent oxygen entering food
Minimise double bonds
Antioxidants
Avoiding initial formation of free radicals
Refining fats and oils
Prevent action of enzymes - blanching
Preventing oxygen entering food
Glass or metal container
Control O2 levels inside packaging
Minimise double bond lipids
Naturally saturated fats
Hydrogenation of polyunsaturated lipids
Anti-oxidants
Naturally present
Added to food
Anti-oxidant mechanism
Most food antioxidants react with a free radical to become a free radical themselves
But it is stable to does not propagate
Some facilitate termination - antioxidant reacts with further free radicals
Few antioxidants react with product to remove rancid flavour
Anti-oxidant compounds
Natural Vitamins
Natural other compounds
Synthetic
