Effect of cooking pretreatment on frying process of eggplant and evaluation of kinetic of oil absorption and moisture changes of eggplant during deep fat frying and cooling period

Frying technology is one of the oldest of food preparing that it used in household and industrial scale, widely. Due to the increasing tendency of consumers to use low-fat products, efforts to reduce oil uptake in fried products has been done. Eggplant absorbs high amount of oil during frying because of high amount moisture and porous texture. In this study effect of different frying times (90, 120, 150 and 180 seconds) and cooking times (1, 4, 7 and 10 minutes) on mass transfer kinetic (oil and moisture)eggplant samples during deep fat drying and cooling period was investigated. Results of analysis variance (ANOVA) showed that independent variables on oil and moisture content was significant (p<0.05).Results of this study showed that cooking pretreatment (hot water and atmospheric pressure) 60 %, decreased oil content in comparison with which did not any pretreatment (control). In mention that cooking time 7 minutes had higher than effect on oil content decreasing (72%). To investigate the kinetic relationships, eggplant samples for 1, 3, 5, 8, 10, 12, 15, 30, 60, 75, 90, 120 and 150 seconds were fried and after each stage of oil and moisture were measured. In addition, at the end of each of these times, were immediately removed from the oil in order to measure the surface oil, immersed in ether, and the amount of oil absorbed (structural) and surface oil samples were measured.Results of mass transfer kinetic during deep fat frying at 180°C, showed that oil content fried eggplant had maximum value on the first time of deep fat frying process and then decreased. Also fried eggplant moisture content decreased, quickly and then velocity of reducing the moisture content of the samples, also declined.