The dangers of cooking oil

BY Angela Jordan

It would be ideal to utilise new cooking oil each time a product is fried, but this is not economically viable for the manufacturing and hospitality industries. We know that utilising old oil is bad for one’s health. Let us explore why old oil is bad for your health and what steps can be taken to ensure that the oil that you utilise is still safe.

After repeated use, cooking oil becomes rancid, which means that the oil could contain carcinogenic free radicles. The oil undergoes chemical changes when exposed to heat and light. These changes can cause potentially harmful substances to be released into the oil. The rate of breakdown would depend on the type of oil – the higher the unsaturated fats, the higher the rate of breakdown.

According to South African regulation 1316 ‘Edible fats and oils used for frying foods are deemed harmful or injurious to human health, unless they contain less than 16% polymerised triglycerides and less than 25% polar components’.

Many of us do not have access to test kits to determine when cooking oil is past its safety use time. There are some easy tell tail signs to when oil should be replaced:
- foam on top surface
- Inability to reach frying temperature without smoking
- dark, dirty look
- musty aroma


There are some test strips and kits available that test the free fatty acids and total polar materials in oil to determine when it should be disposed of.

How many times can cooking oil be reused? Unfortunately this cannot be quantified, as it depends on the type of oil used, the product being fried, frying utensil and frying temperatures.


Helpful tips for oil reuse:
- Shake off excess batter before frying
- Do not fry foods at over 190C. Frying over this temperature can increase levels of 4-hydroxyl-2-trans-nonenal in oil. This is a toxic substance which can increase the risks of strokes, atherosclerosis, Alzheimer’s, Parkinson’s and various liver diseases.

- Turn off heat after cooking
How would one discard used cooking oil? It would not be advisable to discard cooking oil down the drain. The best option would be for it to be recycled. Used cooking oil can be used to make biodiesel fuel.

For additional information on used cooking oil, have a look at the following helpful site: myoilguide.ufs.ac.za 


 July 09, 2015
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Food Safety
Angela Jordan

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