After frying some delicious banana fritters (‘pisang goreng’ / ‘Chuối Chiên’ / ‘Noum chek chien’ / ‘Maruya’) or chicken wings, how many of us are tempted to keep the leftover oil for use later? It still looks ‘clean’ and ‘fresh’ right? Well, best not to overdo it.

In an attempt to conserve cooking oil, many of us would, one time or another, reuse our cooking oil a number of times when cooking at home.

More so for hawkers at ‘night markets’ or ‘pasar malam’, who sell deep-fried street snacks and even fast-food restaurants which repeatedly reuse oils that are maintained at high temperatures. Little do they know (or they know but for economic reasons, choose to turn a blind eye) that what they are doing actually poses great danger to people’s health.

Here are some reasons why it’s not ideal to reuse cooking oil :

1. Most cooking oils contain small amounts of malondialdehyde – a possibly carcinogenic substance that affects enzymatic activity, speeds up the proces of aging, and is cytotoxic. The malondialdehyde level in oil will INCREASE TEN TIMES or more when the cooking oil is used repeatedly.
2. The cooking oil used for deep frying is keept at higher than boiling temperatures for extended periods of time. This causes unsaturated fatty acids (unstable in nature) in plant oils to oxidize continuously, resulting in the formation of harmful, or even carcinogenic substances.
3. Cooking oil that is used repeatedly will have a lowered smoke point and it should be noted that toxic substances are produced more easily in such oil.