Chemical reactions taken place during deep-fat frying and their products : a review

Abstract EN

Deep-fat frying at 180 °C or above is one of the fastest, oldest and simplest methods used for food cooking.

It involves heating an edible oil or fat, and uses the hot oil to cook food.

During deep- fat frying, the oil is exposed to elevated temperatures in the presence of air and moisture.

Under these conditions a series of complex reactions such as oxidation, free radicals, hydrolysis, isomerization, and polymerization take place during the deep-fat frying course and influence quality attributes of the final product such as flavor, texture, shelf life and nutrient composition.

The influence of these reactions results from a number of their products including volatile compounds, hydrolysis products, oxidized triacylglycerol monomers, cyclic compounds, trans configuration compounds, polymers, sterol derivatives, etc.

which are present in both frying oil and the fried food.

In addition, these reactions are interacted and influenced by various impact factors such as replenishment of fresh oil, frying conditions, original quality of frying oil, food materials, type of fryer, antioxidants, and oxygen concentration.

High frying temperature, the number of frying, the contents of free fatty acids, polyvalent metals, and unsaturated fatty acids of oil decrease the oxidative stability and flavor quality of oil.

However, repeated use of frying oils produces undesirable constituents that may cause health hazards.