INTENSIFICATION OF ANTHOCYANIN EXTRACTION BY PULSE ELECTRIC DISCHARGE

Abstract

Physical methods for intensifying the extraction process are used to accelerate mass transfer in the "solid-liquid" system in order to more complete and faster extraction of dyes. The use of electric pulsed discharges, under the influence of which there is an intensive mixing of the mixture of plant materials and extractant, thinning or complete disappearance of the diffusion wall layer of the cell, and an increase in the convective diffusion coefficient, is promising. The article is devoted to the study of the process of extraction of dyes from frozen pomace of red grapes of the Vitis Vierul variety. The improvement of extraction was carried out due to the pretreatment of plant materials with a pulsed electric discharge. The degree of anthocyanins extraction was calculated according to the pH-differential method with measurement of the optical density of the obtained extracts on a Spekol 11 device. As a comparative experiment, we used the extraction of coloring matter from grape pomace with an aqueous solution of 1% by weight hydrochloric acid at pH 2.0 and a temperature of 60°C in several stages until the exhaustion of raw materials to determine the maximum possible amount of extracted anthocyanins. The optimal conditions for the process were chosen: extraction module, duration and number of stages. It was established that the optimal processing time for a raw material:extractant ratio of 1:100 is 30 s, for 3:100 and 5:100 – 60 s. When using a one-stage extraction (hydromodule 20 duration 30 s) with an aqueous solution with the addition of citric acid, the yield of anthocyanins is 51%, in three stages – 77%. The destruction of anthocyanins during storage of extracts at temperatures of 3 and 20ºC for three and six days and the contamination of hoods with products of erosion of metal electrodes were investigated. It was established that when extracts are stored in a dark room at 3ºС, anthocyanins are destroyed by 18% in 6 days, and by 57% at 20ºС.