OPTIMIZATION OF VACUUM FRYING CONDITIONS OF EGGPLANT (Solanum melongena L.) SLICES BY RESPONSE SURFACE METHODOLOGY

Due to the global trend to consume low-fat products, efforts are being made to reduce oil uptake in fried products. In this paper, the effect of pretreatments and parameters of the vacuum frying process on quality attributes of purple creole eggplant slices is presented. A lab-scale vacuum fryer was used to perform vacuum frying at a maximum pressure of 30kPa. Numerical optimization was carried out using the response surface methodology (RSM) through a randomized Box-Behnken experimental design, with three factors: frying temperature (120, 130 and 140 degrees C), frying time (120, 210, and 300s) and pretreatment (control, blanching and drying), which were established through preliminary tests. Moisture content and luminance (L*) decreased with increasing temperature and frying time in all processed samples. Oil uptake, color change (Delta E) and breaking force increased significantly with the increase of these same factors. The highest desirability (0.73) was obtained in blanched samples treated at 130 degrees C during 210s. The optimum values in responses were: moisture 64.77%, oil 3.89%, Delta E 16.67, luminosity 82.59, breaking force 0.96N, color 4.65, odor 4.06, taste 4.25 and greasiness 4.35. The correlation coefficients R-2 for the response variables indicated a good fit of the data to second-order regression models. Vacuum frying is an alternative to process eggplant slices with low-oil content and high acceptability.