Amino acids content in liquor wines of the port type made from grape varieties of interspecific origin
Amino acids are the most important group of organic nitrogenous substances in grapes. In the initial period of grape ripening there are few amino acids in grapes. During ripening their qualitative and quantitative composition noticeably changes. The amount of amino acids in grapes depends on variety, climatic conditions, soil composition, ripeness at harvest, method of processing, particularly the duration of contact of must with the hard parts of the bunch and many other factors. At the beginning of alcoholic fermentation there is an active consumption of amino acids by the yeast, and afterwards, as it dies off, the yeast enriches the wine with them. These compounds influence the formation of aroma and flavor of wines, as they are the precursors of many aromatic compounds. The purpose of the study is to establish the features of the biochemical composition of amino acids in liqueur wines of the port type prepared from white hybrid grape varieties. The objects of the study were liqueur wines of port type from white technical grape varieties of interspecific origin: Kristall, Platovskiy and Stanichnyi. Wine material prepared from Aligote variety was taken as a control. On the basis of the conducted studies, it was found that the total sum of amino acids in the experimental sample prepared from the Platovskiy grape variety was significantly higher compared to the other experimental wines (2692 mg/dm3). Proline dominates among the amino acids of all the test samples by mass concentration, its percentage of the total sum of amino acids in the studied wines was: Aligote (control) - 86,3 %; Kristall - 81 %; Stanichnyi - 51,4 %; Platovskiy - 83 %. The highest levels of amino acids arginine (162.5 mg/dm3), and leucine (4.88 mg/dm3) were observed in the wine made from Stanichnyi. The experimental variant of the variety Platovskiy had a fairly high content of ß-phenylalanine (23.67 mg/dm3) compared with other, and the highest amount of valuable amino acids: tyrosine - 63.07 mg/dm3; serine - 24.01 mg/dm3; threonine - 138.6 mg/dm3; ɑ-alanine - 26.61 mg/dm3. The highest glycine content was observed in the wines prepared from the varieties Kristall (7.24 mg/dm3) and Platovskiy (7.89 mg/dm3).