Experimental design, modeling, and optimization of high-pressure-assisted extraction of bioactive compounds from pomegranate peel

Pomegranate peels are very rich in bioactive compounds, particularly antioxidants, that when properly extracted, may be used for different applications such as food, cosmetics, and pharmaceutics. In this paper, we studied the effect of high-pressure extraction on antioxidant activity and bioactive compounds (total phenolics, tannins, flavonoids, and anthocyanins) of pomegranate peel, using a Box-Behnken design to evaluate the effects of pressure, extraction time, and ethanol concentration to estimate the optimum extraction conditions by response surface methodology (RSM). Individual phenolics, tannins, and anthocyanins were also identified and quantified using the optimum extraction conditions identified by RSM. The results indicated that a quadratic polynomial model could be used to optimize high-pressure extraction of bioactive compounds from pomegranate peel (R (2) higher than 0.90). Ethanol concentration was the variable with higher impact and high pressure increased in average 13% the extraction amount of bioactive compounds. The optimum extraction conditions were similar for all compounds (except for anthocyanins) ranging between 356 and 600 MPa, 32 and 56% of ethanol, and 30 min of extraction time. A pressure of 492 MPa, extraction time of 30 min, and an ethanol concentration of 37% were found to result in the highest amount of the quantified individual compounds. Analysis of variance indicated a high goodness of fit of the used models and adequacy of response surface methodology for optimizing high-pressure extraction. The pomegranate peels are industrial by-products that are rich in bioactive compounds and the results obtained in this work show that high pressure is a promising process for scale up of extraction processes. However, pilot plant tests at higher scale will be necessary to ponder the economic viability of the process.