Lipids - Rancidity and Toxicity

Question 1

Rancidity and Toxicity

Answer 1

Dietary lipids are prone to rancidity, generating compounds which are highly detrimental to health.
* Fatty acids within triglycerides go rancid by releasing the fatty acids from glycerol. Unsaturated fatty acids within triglycerides also go rancid when the double bonds are oxidised.
* Fats are more prone to oxidation if they:
o Are high in polyunsaturated fat.
o Are exposed to prolonged heat, light or oxygen.
o Are naturally low in antioxidants.
o Are refined or heavily processed.
Rancidity results in unpleasant odours and flavours.
* Fats break down into compounds that are subsequently transformed into products such as aldehydes, ketones and hydrocarbons.
* Oxidation of the double bonds generally leads to the production of malondialdehyde.
* Malondialdehyde is a potential mutagen and is found in some hydrogenated or overheated fats.
* Due to the lack of double bonds in saturated fatty acids, they are considered more stable and less prone to oxidation / rancidity. This explains why coconut oil is stable for cooking.
malondialdehyde = a very reactive compound that induces oxidative stress