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.
Highlights
Grape pomace is the natural solid waste left over from winemaking activity
Grape pomace is a source for such valuable substances as polyphenols, organic acids, grape oil and pectin [18]
It is necessary to acquire new knowledge on physicochemical parameters and properties of grape pomace resulting from processing of various grape varieties with the use of new technological patterns and equipment
Summary
Grape pomace is the natural solid waste left over from winemaking activity (pressing grapes into wine). Grape pomace is a source for such valuable substances as polyphenols, organic acids, grape oil and pectin [18]. The quantity of pomace varies widely depending upon the grapes’ varietal peculiarities, and processing technologies applied. The average composition of grape pomace is the following: skins – 37 to 39%; pulp – 30 to 32%; seeds – 28 to 30%; stalks – 1.1 to 1.5%; grapevine leftovers – 0.2 to 0.3% [11,12]. It is necessary to acquire new knowledge on physicochemical parameters and properties of grape pomace resulting from processing of various grape varieties with the use of new technological patterns and equipment. The objective of our work was to obtain new data on physicochemical properties and chemical composition of high-molecular compounds of grape pomace, depending upon the grape variety and processing technology applied
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