Evaluation of Ultrasound and Blanching Pretreatment on Physicochemical Properties of Deep Fat Fried Zucchini

Deep-fat fried foods have great popularity owing to their desirable sensory properties. However, negative impressions toward fried foods have been created due to their high fat absorption. Pretreatments such as thermal blanching or ultrasonication could aid the production of fried foods with less fat and desirable quality attributes. The present study was therefore aimed at exploring the effects of blanching (0-4 min) and ultrasonication (0-40 min) pretreatments on the moisture, oil absorption, shrinkage, hardness and color parameters of zucchini fried at different at temperatures (130-180 ºC) for different times (4-6 min) using response surface methodology. The results of the statistical analysis revealed that as the frying process prolonged, moisture content decreased and fat absorption increased. However, higher process temperature led to both lower moisture content and fat absorption. It was observed that the blanching and Ultrasonication pretreatments both resulted in lower fat absorption due possibly to their decreasing effect on the moisture loss during frying. As expected, while frying at a higher temperature and longer duration caused greater shrinkage, the pretreatments affected it conversely. Hardness had a Ushaped relationship with frying duration, i.e. the softest texture was obtained at the middle levels of frying time. However, frying temperature steadily increased product hardness. As well, the blanching and ultrasonication pretreatments were accompanied by decreased in hardness. The results showed that while an increase in temperature and duration of the frying process was concomitant with the lower lightness of the sample, the pretreated samples experienced a lower decrease in these color parameters. In conclusion, the optimum frying condition was found to be blanching for 3.94 min, ultrasonication for 40 min, the frying temperature of 163.19 ºC and a frying time of 4 min