Optimal operational variables of phenolic compound extractions from pistachio industry waste (Pistacia vera var. Kerman) using the response surface method

Abstract

San Juan is a leading pistachio producer in Argentina. Pistachio industrial processing generates biowastes that can be reused. These biowastes can be used as a precursor of bioactive components of interest as the phenolic compounds. Therefore, the aim of this work is to optimize the conditions of stirring extraction (SE) and ultrasonic-assisted extraction (UAE) of phenolic compounds (PC) using response surface methodology (RSM). A central composite design (CCD) was used to analyze the effects of the independent variables: ethanol:water ratio and extraction time. The optimal conditions for extraction of phenolic compounds from pistachio industry biowaste through UAE method were a volumetric ratio of ethanol:water ratio about 0.5 and an extraction time between 0.7 and 0.94 h. For SE, the optimal conditions were a volumetric ratio of ethanol:water ratio about 0.6 and an extraction time between 2 and 2.7 h. Longer period of extraction, for both extractions UAE and SE, produces degradation reactions and therefore a radical capture activity loss. SE had optimal values of volumetric proportion solvents comparable with those corresponding to UAE. But SE requires more time to produce breaks in the cell, and dissolution and diffusion of bioactive compounds in the extracts.