Model development and process optimization for solvent extraction of polyphenols from red grapes using Box-Behnken design.

The objective of the present study is to find out the optimum extraction conditions for extraction of polyphenols from red grapes using Box-Behnken design. Red grapes polyphenols were extracted using acid-ethanol solvent at various extraction temperature (40-60°C), extraction time (20-100 min) and different solid-liquid ratio (1:5-1:15 g:ml). The effect (main and interactive) of extraction conditions on total anthocyanin, phenolic and flavonoid content were studied using Box-Behnken design (three factors at three levels). The results showed that the contribution of the quadratic model was significant for all the responses. Second-order mathematical regression models were developed and were found to fit well with observed data. Derringer's desirability function methodology was performed to find out the optimal conditions based on both individual and combinations of all responses (extraction temperature: 57°C, time: 61 min, and solid-liquid ratio: 1:8.7 g:ml) were established. At this optimal condition, the anthocyanin yield, total phenolic and flavonoid content were 73.92 mg/100 g, 221.4 mg GAE/100 g, and 79.08 mg CE/100 g, respectively. A desirability value of 0.902 was achieved at this point.