Results and Discussion The effects of ultrasound, electric field strength, the time of applying the field and sonication time on a number of E. coli, and energy consumption of the process in mint distillate were investigated. As shown in Table (), the full quadratic model for the data had a significant effect on the reduction of E. coli in the samples of mint distillate. The adjusted determination coefficient, standard error and coefficient of variation (C.V) of the model were equal to 0.9984, 0.049 and 2.39, respectively. According to ANOVA (Table 1-4), with the exception of the electric field strength coefficient* sonication time and the time of applying the electric field * sonication time, other coefficients of the variables in the model …show more content…
the objective function was Equation (1-4). The goal of this optimization was to achieve a situation of independent variables (field strength, retention time, power of ultrasound and sonication time), in which with the lowest energy consumption, the amount of E. coli in the sample is equal to zero. Boundary conditions specified in optimization was that the values of the independent variables are in the range of the experiment. All independent and dependent variables by reason of the same importance, the weight of one was given, and at the end, minimizing the value of the objective function was selected (Table 4-2). The optimum values for field strength, retention time, power of ultrasound and sonication time were equal to 10 kv/cm, 35s, 185.90 w, 4.47 min, respectively. For the values above-mentioned, the number of remaining E. coli was equal to zero. Finally, to verify the optimal point, the independent variables were rounded down the nearest integer to have practical applicability. Accordingly, field strength, retention time, power of ultrasound and horn sonication time were equal to 10 kv/c, 35 s, 200 w and 5 min, respectively. The amount of reducing the number of E. coli in the laboratory was equal to zero, indicating the accuracy of the method of optimization and