Physical and thermal properties of potato chips during vacuum frying

Vacuum frying (1.33 kPa), with the aid of a de-oiling mechanism, was used to produce low-fat potato chips. The kinetics of oil absorption and oil distribution in the potato chips was studied so that effectiveness of the de-oiling system could be established. Non-linear regression was used to fit the experimental data to the models used to describe oil absorption in potato chips with time. Moisture content, oil content, microstructure, diameter and thickness expansion, bulk density, true density, and porosity of chips fried at different temperatures (120, 130, and 140 C) was performed to evaluate the effect of process temperature on the product. The convective heat transfer coefficient at the oil-chip interface was determined for the same temperature range. The final oil content of the potato chips was 0.072 +/- 0.004, 0.062 +/- 0.003, and 0.059 +/- 0.003 g/g solid for frying temperatures of 120, 130, and 140 degrees C, respectively. These values are lower (80-87% less) than those found in the not de-oiled potato chips, which indicates that the de-oiling mechanism is crucial in vacuum frying processing. A significant difference (P < 0.05) was observed in oil content and oil distribution within temperatures. The rate of change in product quality attributes was greatly affected by temperature; however, the final values of moisture content, bulk density, true density, porosity, diameter shrinkage, and thickness expansion were not affected by temperature. During vacuum frying, the convective heat transfer coefficient changed considerably as frying progressed; moreover, it increased with temperature reaching a maximum between 2200 and 2650 W/m(2) K depending on frying temperature. (C) 2010 Elsevier Ltd. All rights reserved.