Process Optimization in Vacuum Frying of Kiwi Slices Using Response Surface Methodology

Vacuum deep-fat frying is a new technology that can be used to improve the quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper the effect of frying process parameters, namely frying time, frying temperature and pressure on the quality factors of fried kiwi slices was studied. A laboratory scale vacuum frying apparatus was used to study the interactions and optimization of process parameters on the vacuum frying of kiwi fruit. Considering the results of pretests, the variables ranges were assumed as 80-120 °C for the temperature, 40-150 mbar for the vacuum pressure and 5-20 minutes for the processing time. The results indicated that the color and the shrinkage were significantly (p<0.05) correlated with the frying temperature and time, while the crispiness was affected only by the frying temperature. There was no significant relation between the vacuum pressure and the responses except the shrinkage. The results of sensory evaluation indicated that there were no significant differences (p<0.05) between the vacuum fried kiwi slices and the dried kiwi chips except flavor. The optimum conditions for the vacuum frying of kiwi slices were found to be: 105ºC, 62 mbar, and 8 min, for the frying temperature, the vacuum pressure and the frying time, respectively.