Introduction. Any waste can become a raw material for new products. Therefore, waste should be considered as secondary material resources. Grape pomace is the basic waste of wine industry, and research in its chemical composition may allow for a more effective recycling of food industry waste. Study objects and methods. The research featured sweet and fermented pomace of white and red grapes, namely “Chardonnay”, “Sauvignon Blanc”, “Riesling”, “Pinot Blanc”, “Traminer Pink”, “Viognier”, “Morava” “Pinot Noir”, “Roesler”, “Cabernet Sauvignon”, “Merlot”, “Saperavi”, and “Rebo”. They were obtained in the production of wines at wineries in the Krasnodar region. Mass concentrations of organic acids and cations of alkaline and alkaline-earth elements were determined in extracts by capillary electrophoresis. The data was converted to dry matter. Moisture content was calculated as a percentage of the change in the mass of grape pomace. Results and discussion. The moisture content of sweet pomace varied from 49.33 ± 2.04 to 70.35 ± 0.60%, and in fermented pomace – from 47.49 ± 0.02 to 64.24 ± 0.60%. The varieties were studied for mass concentrations of tartaric, malic, succinic, citric, and lactic acids. Tartaric and malic acids proved to be the most abundant ones. The pomace of Riesling grapes had the greatest amount of tartaric acid (104.47 ± 4.16 g/kg). The “Chardonnay” variety proved rich in malic acid (19.40 ± 2.67 g/kg), while the “Morava” pomace had the biggest amount of citric acid (12.61 ± 1.12) and succinic acid (11.72 ± 1.23). The research also defined concentrations of alkaline and alkaline-earth elements. Their content ranged from 41.04 to 3.29 g/kg. Potassium appeared to be the main cation in the pomace samples. The share of potassium in the total mineralization of pomace was up to 94%. The “Riesling” variety grown near Novorossiysk had the largest amount of potassium (36.46 ± 4.65 g/kg). The samples demonstrated a significant correlation between the content of tartaric acid and potassium. Conclusion. The research revealed a significant variation in the concentration of the organic acids and cations of alkaline and alkalineearth metals, depending on the grape variety, the place of its growth, and processing. The grape pomace samples differed moisture content. It depended on the volume of the liquid fraction, i.e. wort or wine material selected during pressing.
The article is devoted to the research of the makeup of phenolic compounds and fatty acids of grape pomace. The phenolic compounds were identified in skin and seed extracts and in extracts of skin-and-seed mixtures; the fatty acids – in grape oil generated by direct pressing. It was established that anthocyanins were present mainly in the skins. Low concentrations of ten components of the anthocyanin complex were identified in the Saperavi seeds. Maximum amounts of anthocyanins were found in the Saperavi skins. The concentration of quercetin distinguished by a PP-vitamin activity was by 1.5 to 2.0 times higher in the skin-andseed mixtures, especially of Roesler grapes, than in the skin itself. Maximum amounts of flavan-3-ols, hydroxy-cinnamic and hydroxybenzoic acids and oligomeric procyanidins, as well as the highest antioxidant activity were observed in the skin-and-seed mixture. The highest value of the correlation factor was observed in cases of interaction of antioxidant activity and concentration of procyanidins (r = 0.83), antioxidant activity and concentration of anthocyanins (r = 0.78), and antioxidant activity and concentration of flavan-3-ols (r = 0.75). Among the flavan-3-ols, it was (+)-D-Catechin that prevailed in grape seeds, with its concentration in the Pinot Noir extract (OAO APF Fanagoria) reaching 468 mg/dm3. Maximum concentration of Epigallocatechin-gallate was observed in the Saperavi and Pinot Noir seeds. As regards the concentration of hydroxy-cinnamic acids in the seeds, n-coumaric acid (Ancellotta, Saperavi) stood apart among the others; gallic acid (Saperavi, Ancellotta) came forward among the hydroxy-benzoic acids. In the reviewed samples of grape seeds, procyanidins of groups В1 , В2 and В3 distinguished by high antioxidant activity prevailed. Prevalence of linoleic and oleic acids was established for grape oil extracted from the seeds of such red grape varieties as Cabernet Sauvignon, Pinot Noir and Saperavi. Maximum concentrations of oleic acid were found in the Pinot Noir and Riesling seeds. Palmitic and stearic acids were also available in rather high concentrations in the grape oil.
Experimental data on the content of biologically valuable components in grape pomace are presented. The presence of organic acids was revealed in an amount from 33.35 g/kg (Saperavi) to 108.2 g/kg (Rebo). The main acid is tartaric. Phenolic compounds have been identified: anthocyanins, flavones, flavan-3-ols, oxycinnamic and hydroxybenzoic acids, procyanidins. The main anthocyanins found in grape pomace are the 3-O-glycosides of malvidin, petunidin, cyanidin, peonidin and delphinidin. The highest total content of hydroxybenzoic acids was in the pomace of Pinot Noir grapes – 720 mg/kg, further in descending order of concentration followed by pomace from Saperavi grapes (708 mg/kg), Cabernet Sauvignon (681 mg/kg), Merlot (575 mg/kg) and Rebo (545 mg/kg). The highest total content of vitamins was found in the pomace of Rebo grapes – 639 mg/kg, the lowest – Merlot (471 mg/kg). In all samples, vitamin B1 prevails, then in decreasing order – ascorbic acid, vitamins B2, B3, B5, B7. Moreover, their concentrations vary significantly depending on the grape variety from which the pomace is obtained. The influence of the grape variety on the content of these biologically valuable components in the pomace has been established, which must be taken into account in the production of biologically active substances that increase the nutritional status of a person.
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