Interactions between fat and food during deep-frying

In deep-fat frying the food is completely surrounded by the frying fat or o il and different events occur within a few minutes: dehydration of food sur face, absorption of fat, formation of flavour compounds, development of sur face colour, etc. Due to the drastic conditions applied during deep-frying, the frying fat also undergoes degradation. Although much work has been don e on modifications of used frying fats and oils under different conditions, changes in the fried substrate have been much less studied. Particularly, there is minimal information on some physical and chemical aspects of the i nteractions between frying fats and fried foods. In this paper the main cha nges in the frying fat due to the nature of the food fried in it as well as modifications in the food as a consequence of the fat or oil used as heat transfer medium are reviewed. Fat absorption and lipid exchanges are the ma in physical changes involved. Chemical reactions include interaction betwee n food constituents and oxidised lipids as well as hydrolysis of frying fat s due to food moisture.