A new alcohol oxidase-peroxidase method of ethanol assay in fermented musts and wine products is described and compared to conventional methods routinely used in winemaking. The sensitivity, accuracy, and reliability of this method were determined. The results of ethanol determination in fermented musts and wines correlated well with the data obtained by refractometry (correlation coefficient R = 0.9595, p < 0.0001) and densitometry (correlation coefficient R = 0.9384, p < 0.0001). The proposed method is less time-and laborconsuming and allows simultaneous analysis of a series of wine samples.
The work presents the possibility of obtaining polyphenol concentrates from raw materials (pomace, seeds, cane, vines, leaves) of Crimean grapes of white varieties Aligote, Rhine Riesling, Rkatsiteli and grapes of red varieties Muscat Hamburg, Cabernet-Sauvignon, by vacuum concentration of alcoholic extracts of grape raw materials. An experimental assessment on the qualitative and quantitative structure of polyphenols, the basic functional ingredients of biological activity of grapes has been given. It has been established that by concentration of phenolic substances, the concentrates are distributed in the following sequence: seeds of grapes of white and red varieties, stalks of grapes of white and red varieties, pomace of grapes of red varieties, leaves of grapes, vine of grapes, pomace of grapes of white varieties. In grape concentrates, anthocyanins, flavones, flavan-3-ols, oligomeric and polymeric procyanidins, oxycinnamic and oxybenzoic acids and stilbenoids have been identified. The maximum quantitative evaluation of stilbenoid concentration obtained in grape concentrates was up to 5.0 g/L, which is by order of magnitude greater than in red wines. The antioxidant activity indicator (AOA), estimated in vitro in grape seed concentrate, ranged from 180.0 to 250.0 g/l, which is by order of magnitude greater than in red grape wines.
The paper experimentally assesses the characteristics of grape raw materials (vines, leaves) in terms of quantitative and qualitative composition of polyphenols - the main functional biologically active ingredients of grape processing products. For obtaining alcoholic extracts, vines and leaves of grape were pre-dispersed and extracted using the ethanol. The extraction was carried out at room temperature for several months until an equilibrium concentration of polyphenols was obtained. The extracts were separated by leaking off on a sieve. The qualitative and quantitative composition of polyphenols in alcohol extracts was determined by the HPLC method. The analysis of the obtained data shows that a broad array of polyphenols appropriate for grape pomace, seeds and stalks (flavones, flavan-3-ols, hydroxy-cinnamic, oxybenzoic acids, stilbenes, oligomeric and polymeric procyanidins) is present in vine and leaves.
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