Shrinkage kinetic modeling of potato strips pretreated with ultrasound and microwave during deep-fat frying process

The aim of this study was to investigate the effects of process conditions as well as ultrasound and microwave pretreatments on shrinkage of potato strips during deep-fat frying process. Ultrasound pretreatment was performed at frequencies of 28 and 40 kHz and microwave pretreatment was conducted at powers of 3 and 6 W/g on the potato slices. Then, the frying process was done at 150, 170 and 190°C for 1, 2, 3 and 4 min. According to the results, ultrasound pretreatment significantly reduced the shrinkage of potato strips. However, microwave pretreatment resulted in a significant increase in the samples shrinkage. In addition, frying time as an important process factor had a significant effect on shrinkage; such that by increasing time, shrinkage was increased. Moreover, the results showed that temperature effect on shrinkage is not significant. Furthermore, six models were presented in order to predict shrinkage considering the process conditions and for the models constants, multivariate models were obtained based on multivariate regression analysis as a function of process conditions (ultrasound frequency, microwave power and process temperature).