Optimization of extraction parameters of phenolic antioxidants from defatted grape seeds flour by response surface methodology

Introduction. The optimization results of the conditions of liquid-solid extraction by wine industry waste water in the form of the defatted grape seeds flour in order to obtain the extract with high antioxidant capacity are conducted in this report. Materials and methods. Total antioxidant capacity (TAC) and total phenolic content (TPC) of the samples were determined by the method of galvanostatic coulometric titration with electrogenerated bromine and spectrophotometric method using Folin-Ciocalteu reagent, respectively. TAC and TPC experimental values were presented in terms of the equivalent of gallic acid content (GAE) per unit mass of dry powder (DW). Results and discussion. Response surface methodology (RSM) is used to search for optimal condition of solid-liquid extraction of phenolic compounds from defatted grape seeds flour under the influence of three factors: the temperature (60-100 degrees C), extraction time (90-150 min) and liquid to solid ratio (60-100). The result showed that the phenolic substances yield in the set ranges is 1.20-2.64% with total antioxidant capacity of 17.71-36.78 mg GAE/g DW. Due to optimization procedure, it was determined that under optimal conditions (the temperature of 100 degrees C; the extraction time is 131 min.; and the ratio of the extractive agent volume to the mass of the powder is 85) the maximum TAC of the extract of 37.04 mg GAE/g DW is achieved. The maximum yield of phenolic substances of 2.646% was obtained under the following conditions: temperature of 100 degrees C; extraction time is 117 min.; and the ratio of extraction agent volume to the mass of the powder is 93. When optimization is used with two TAC and YPC response functions, the following optimal conditions were obtained: the temperature of 100 degrees C, the extraction time is 123 minutes and the ratio of extractive agent volume to the mass of powder is 89, at which 36.91 mg GAE/g DW TAC and YPC values and 2.633% were obtained, respectively. The validation of obtained results showed their compliance within 3% with experimental values. Conclusion. The obtained results indicate the perspective of wine industry waste recycling in order to obtain the solid extract from defatted grape seeds flour as a source of biologically active substances of a phenolic nature with high antioxidant potential.