Physicochemical parameters of grape pomace subject to grape processing technology applied

Abstract

This article presents experimental data on physicochemical parameters (humidity, density, bulk density, effective viscosity) of grape pomace of various white and red grape varieties, subject to the processing technology applied. It was established that pomace humidity varies across a wide range of values, subject to the grape variety, grape processing technology and pressure equipment. A study of Chardonnay pomace was used to note the influence of pressure equipment and processing technology upon pomace humidity. The values of density and bulk density had a strong invert correlation with the humidity index. With increase of humidity, the values of density and bulk density lowered both for white and red pomace. It was shown that the value of effective viscosity of pomace of white grape varieties varied from 8.8 (Chardonnay) to 12.8 (Gewürztraminer) Pa·s; that of red grape varieties varied from 13.2 (Pinot Noir) to 15.8 (Saperavi, fermented pomace) Pa·s. Such variation may have been related to the varietal peculiarities of grapes, pomace humidity, and concentrations of high-molecular compounds. The highest total of phenolic compounds was observed in extracts of fermented Saperavi pomace. The total of pectic substances in grape pomace varied from 5.5 to 7.2% of dry weight for the white grape varieties, and from 4.4 to 5.9% for the red grapes. As for the concentrations of pectic substances, Riesling, Pinot Blanc and Sauvignon Blanc pomace were distinguished among the white grapes, and fermented Cabernet Sauvignon pomace – among the red grapes.