Developing a houshold vacuum frying equipment and testing the performance on fried french fries production

In this research, the development of a kitchen appliance frying equipment which can operate either under vacuum or at atmospheric pressure is aimed which will be tested by its performance on the frying of French fries. In order to determine the optimum frying conditions (temperature and time) of the French fries, which was produced using the developed prototype equipment, optimization study was carried out according to Central Composite Rotatable Design (CCRD) and the effects of the temperature and time of vacuum frying was investigated. Pressure which was the another independent variable of vacuum frying was kept constant at 13.3 kPa as the attainable minimum pressure level in theprototypes. At the optimization stage of the study, frying temperature (120-150ºC) and frying time (5-15 min) were selected as the independent factors and their effects were investigated by the means of hardness, oil content, acrylamide content and overall preference which is one of sensory evaluation criteria of French fries. Also, the effect of vacuum frying conditions on the color values (L*,a*,b*, C* and BI), moisture content, pore diameter and sensory evaluation (appearance, color, texture and taste) of French fries and on the total polar material, free fatty acids, acid value and peroxide value of frying oil were determined. The results were evaluated by using Design Expert packaged software and optimum vacuum frying conditions targeting minimum oil content, 30-45 N in range of hardness, minimum acrylamide content and maximum overall preference. The optimum vacuum frying condition was selected as 124.39 °C of frying temperature and 8.36 min of frying time for French fries frying. In order to compare with vacuum frying method, French fries were fried at atmospheric pressure at 2 different temperatures (165 and 180°C) and 4 different times (5, 7.5, 10 and 15 min) and the quality criteria of the French fries and frying oil were compared with the results of the analysis for vacuum frying method. In addition, in order to determine the total using time of frying oil, frying was repeated for 7 times by using the same frying oil at atmospheric pressure and it was repeated for 20 times under vacuum. In order to evaluate the final quality of the frying oil, the total polar material, free fatty acids, peroxide value, conjugated dienes and trienes content of frying oil and color value (L*, a*, b* and BI) and hardness of French fries were determined after each frying process. According to this study, the color values (L*, a*, b*, C* ve BI) of the French fries that were vacuum fried were considerably close to the ones fried at atmospheric conditions. Moisture content of the vacuum fried French fries decreased rapidly than atmospheric frying, whereas pore diameter and hardness of the vacuum fried French fries were higher than atmospheric frying and sensory properties values of vacuum French fries were not significantly different from French fries atmospheric pressure. Also it was determined that the oil content of vacuum tried French fries was higher and acrylamide content of vacuum French fries was lower compared to atmospheric frying. Compared to atmospheric frying, the French fries which were fried at determined optimum conditions for vacuum frying preserved the desired colour, textural properties and flavours and it has lower oil content and reduced acrylamide formation by 88-96%. In addition, the frying oil quality was better preserved with vacuum frying compared to atmospheric frying.