Modeling and Optimization of the Effect of Osmo-Ultrasonic Pretreatment Followed by Hot Air Drying of Black Cherry Fruit

Response Surface Methodology (RSM) was employed to determine the optimum processing conditions leading to maximum anthocyanin، phenolic compound and antioxidant activity during osmo-ultrasonic pretreatment followed by hot air drying of black cherry fruit. Temperature (40، 50 and 60ºC)، sucrose content (40، 50 and 60% w/v) and ultrasound frequency (0، 65 and 130 kHz) were the factors investigated with respect to anthocyanin، phenolic compound and %Ec50 during osmo-ultrasonic pretreatment followed by hot air drying of fruit. Experiments were designed according to Central Composite Design with the three factors each at three different levels. The experiments were conducted with solution to sample ratio of 10/1 (V/W). With respect to the dependent variables، both linear and quadratic effects of all the three independent variables on anthocyanin، phenolic compound and %EC50 were found to be significant (P<0. 05). For each response، second order polynomial models were developed using multiple linear regression analysis. Analysis of Variance (ANOVA) was performed to check the adequacy and accuracy of the fitted models. Optimization procedure was done using RSM to maximize polyphenol and anthocyanin content and as well to minimize Ec50. Optimum conditions for the process were obtained as: 40°C for temperature، 40% for sucrose concentration and 1. 31 kHz for frequency. Predicted values for phenolic compounds، total anthocyanins and Ec50 were recorded as 1. 189 mg eq. galic acid/100g dry matter، 2837. 82 μg/100g dry matter and 0. 0245/mg of dry matter، respectively. The proposed model for the prediction of dependent variables was in very closed match with the experimental results.