Optimizing the Extraction of Antioxidant Components from Grape (Vitis vinifera L.) Skin by Ultrasonic Pre-treatment in Response Surface Method

Abstract

Grapes are one of the most important agricultural products which could be used either as fresh fruit or processed food. In Iran, grapes are very crucial agricultural and commercial products. Every year, a massive volume of grapes waste is made by the units of grape Doshab producers, so the producers are engaging with many problems of waste disposal. Grapes waste is a valuable source of natural pigment and antioxidant compounds specifically polyphenols compounds. Extracting antioxidant compounds from cheap primary materials like grapes waste is a suitable method for various food and pharmaceutical industries. This research aims to find the optimum state of extracting phenolic compounds from Shani grapes skin with 3 independent variables (extraction time using ultrasonic bath, liquid to solid phase ratio and ethanol solvent concentration), by utilizing the response surface method (RSM), and central composite design (CCD). The optimum condition for extraction of this compound was 59.06% concentration of ethanol, 16.08 ml/g liquid to solid phase ratio and 24.12 min extraction time. The phenolic compounds concentrations were measured by high-performance liquid chromatography (HPLC). The research results have shown that the extract of Shani grapes skin contains 8 different phenolic compounds, of which, epigallocatechin and catechin had the highest concentration. Consequently, by finding the optimum condition of phenolic compounds extraction, these compounds could be produced on a pilot scale for utilization in the food and pharmaceutical industries.