Optimization of frying process of zucchini slices by frying combined with predehydration in terms of oil absorption and product texture

In our study, it was focused on the oil absorption amount of zucchini vegetable being widely consumed and primarily preferred after fried by deep-fat-frying method. Main objective is to partially decrease the moisture content of this vegetable by predrying process due to its direct relation with oil absorption and as a result to decrease the amount of oil absorbed by final fired products. Towards this aim, zucchini vegetable was fried by deep-fat-frying, following to be subjected to the convectional drying, microwave assisted drying, osmotic dehydration, vacuum assisted osmotic dehydration and ultrasound assisted osmotic dehydration. First of all, the effects of frying conditions on textural properties, moisture contents, surface color parameters and particularly on oil absorption were investigated. Additionally, deep-fat frying method combined with convectional drying and microwave assisted drying pretreatment applications was optimized by response surface methodology towards our main objective.The most effective drying and following frying parameters towards the aim of less oil absorption and the desired quality characteristics (surface color and texture) were found as 49°C of drying temperature and 11% weight loss during drying for convectional drying and 175 °C of frying temperature and 103 seconds of frying time. For microwave assisted drying, 10% weight loss for drying and 159 °C of frying temperature and 180 seconds for frying time were found to be the optimal process conditions.In samples subjected to the convectional drying the ratio of the desirability for desired responses like moisture %, oil %, surface color and texture exceeded 75%. It was found around 75% for samples dried by microwave assisted drying. Additionally, the effects of vacuum and time on moisture and oil content of zucchini slices predried by osmotic dehydration was found not to be significant (p>0.05). On the other hand, concentration of osmotic solution in all application of ultrasound assisted osmotic dehydration processes was determined to significantly change the moisture and oil content (p≤0.05).At the end of the study, it was concluded that drying of zucchini slices using pre-drying processes before frying limits the amount of oil absorption which is crucial point in terms of human health.