We love frying food because of the taste and texture. It looks delicious! I do love crunchy and crispy fried potato or fried chicken. Who does not, you really have weird taste. Get a doctor! For those who did kitchen work, it quite often we reuse the cooking oil because we don’t want to waste it. Especially when we are running a food business. We want to cut costs, reuse cooking oil does matter. Do you ever wonder how many times you should use your cooking oil for frying? Is it safe to reuse our cooking oil? You need to know this because it good for you and your customer as well.
Science explained
Chemically, anything exposes to heat would not necessarily be the same as it was. What I meant is that, if you heat aluminum it still be aluminum because it can transmit heat. This material is known as a good conductor such as aluminum foil. If you heat pure water, it evaporates become vapor. But if water vapor condensed, they turn back to liquid water. It remains the same because there was nothing for them to react with and remain stable in their original state.
In the case of cooking oil, it contains oxygen, more than water could hold. In the presence of oxygen, oils expose to the oxidation reaction. It means the oil is broken down into something else. During frying, more impurities dissolve in the oil and take part in a series of complex reactions (i.e., hydrolysis, polymerization & etc.). This process becomes faster when you cook at high temperatures.
What expert said
New compounds formed after frying such as aldehyde and carboxylic acid. These compounds may put our health at risk. Experts suggest that the quality of the oil degraded faster when used at high temperatures and depends on the type of food you fried. It depends on the type of oil as well (Park et al., 2016)
What to do
As a best practice, cook at high temperature when necessary only and don’t expose the oil to air. Discard it when turned dark in color. Fresh oil always the best.