Optimization and comparison of different techniques for extraction of flavonoids of Bulgarian Mavrud grape by-products

Abstract

In recent years, the interest in antioxidants in grape by-products has increased significantly as scientific research for the extraction and quantification of these compounds. In the present investigation was optimized the antioxidant yield of the grape pomace and seeds discharged as waste from the Bulgarian Mavrud winery, near to Trakiets village. There is a lack of information about extraction optimization and utilization of the selected grape by-products. The aim of the paper was studying the influence of some process parameters: effect of the degreasing pre-treatment of the material, effect of the extraction method and the extraction time on the yield of total flavonoid and anthocyanin contents and Trolox equivalent antioxidant capacity (TEAC). For this propose the extraction kinetics were obtained by using conventional and non-conventional extraction methods-magnetic stirring and ultrasound-assisted extraction (UAE) and using of degreased and non-degreased plant material. Degreasing was done by conventional Soxhlet extraction with n-hexane for an hour. All analyses were done using ultraviolet-visible (UV-vis) spectrophotometry. The results obtained show that the applied ultrasound power after the degreasing pre-treatment promoted optimal anthocyanin and flavonoid recovery for 180 minutes extraction time of both-grape pomace and seeds. The TEAC is not affected by applying UAE and degreasing pre-treatment technique. The optimization of the extraction conditions is important because it could alter an economic impact on the extraction evaluation of the Mavrud grape by-products. The grape pomace and seeds from Bulgarian Mavrud wine-making can be used to obtain secondary derivatives with high-added antioxidant value.