Abstract:
The article focuses on the optimization of the extraction process of biologically active compounds
(BAC) from grape marc—a by-product of the wine industry. The influence of temperature,
specifically 30 °C, 45 °C and 65 °C, and ethanol concentration in solutions, specifically 0–96% (v/v)
on the extraction yield of polyphenols, flavonoids, tannins and anthocyanins, were investigated.
The composition of individual polyphenols, anthocyanins and organic acids, antioxidant activity
(DPPH and ABTS) and CIELab chromatic characteristics of the grape marc extracts (GME), were
characterized. The microbiostatic and microbicidal effects in direct contact of GME with pathogenic
microorganisms, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, were
determined in vitro. The influence of extraction parameters on the total polyphenol content (TPC),
total flavonoid content (TFC), tannin content (TC), total anthocyanin content (TAC) and their interdependencies
were studied using information analysis. A mathematical model was developed on cubic
spline functions. The analysis of individual compounds showed the presence of a wide range of
flavonoids (procyanidin B2, procyanidin B1, hyperoside and quercetin), flavones (catechin), hydroxybenzoic
acid derivatives (gallic, protocatechuic, p-hydroxybenzoic acids, m-hydroxybenzoic acid,
syringic acid), hydroxycinic acid derivatives and ferulic acid methyl ester. The malvidol-3-glucoside
was the main anthocyanin identified in the extract. A high amount of tartaric acid was also found.
GME showed significant antimicrobial activity against Gram-positive bacteria and lower activity
against Gram-negative bacteria.
