Comparison of the deep frying process in coated and uncoated dough systems

The effect of an edible methylcellulose coating to reduce oil uptake during frying was analyzed on a dough system. The oil uptake reduction was 30% for coated dough discs compared to uncoated ones; the coating neither modified the water content of the samples nor the quality attributes of the fried dough such as color and texture. A mathematical model was developed including simultaneous heat and water vapor transfer at the different stages of the frying process and the cooling at environmental conditions after the product was removed from the fryer. It allowed to simulate satisfactorily the experimental data of temperature profiles, water losses and the thickness of the dehydrated zone (d(T)) as a function of frying time. Post-frying oil uptake was correlated with d(T) considering microstructural changes during frying time, analyzed by SEM (scanning electron microscopy). The coating reduced oil uptake, modifying the wetting properties related to the interfacial tension and also becoming a mechanical barrier to lipids. (C) 2007 Elsevier Ltd. All rights reserved.