Simulation and ability to control the surface thermal history and reactions during deep fat frying

This paper discusses the possibility to control the reactions, which occur at the surface of the product during frying, when the final water content is imposed. Considered frying conditions include frying at constant temperature and frying with a variable oil temperature as encountered in industrial continuous deep fryers. For a raw material similar to potato, two inverse models of coupled heat and mass transfer are proposed to reconstruct the surface temperature while taking into account a possible internal transport of water and the hygroscopic properties of the food matrix. The tested reaction scheme is a simplified version of Maillard reactions involving a reducing sugar and an amino acid. Results are expressed as the variation of the surface thermal histories for different water contents and as cumulated amounts of Amadori rearrangement products. Since the intrinsic activation energy in solids at temperature above the boiling point of water are poorly described in the literature, several scenarios with a wide set of values between 20 and 90 kJ mol−1 are considered. The discussed effects include: thickness, initial water content, oil temperature, and internal liquid water transport. Finally, the benefit of non-isothermal frying temperatures is examined.