Alcoholic Fermentation, Chemical Composition and Organoleptic Profile of Spontaneously Fermented White and Red Wines

Abstract

The development of viticulture and winemaking, including the preservation and cultivation of old local grape varieties, is an opportunity to preserve traditions and diversity of vine genetic resources in Bulgaria. This research was a part of the DIONYSOS project, investigated the biological diversity of local varieties grown in different regions of Southern Bulgaria. The subject of the current study were 10 grapes samples from 3 white (Dimyat, Red Misket, Tamyanka) and 3 red (Pamid, Mavrud, Gamza) autochthonous to Bulgaria wine grape cultivars grown in the region of Haskovo district. The aim was to determine the chemical composition and organoleptic profile of the experimental wines obtained after spontaneous alcoholic fermentation. After crushing, the fermentation of the grape pomace was run under the impact of wine yeast from the natural microflora of the grapes. The dynamics of the process was monitored by daily measurement of dry matter by refractometer. The yeasts showed different fermentation activity. The process onset was between the 48th and 72nd hours and proceeded dynamically and efficiently. The spontaneous fermentation was complete and ensured a high ratio of sugar conversion into alcohol. An exception was observed in both samples of the cv. Tamyanka. The content of residual sugars, alcohol, titratable acids, volatile acids, pH in the experimental wines were analyzed by generally accepted in winemaking practice methods. No deviations were found in the values of the studied indicators and metabolites formed were within acceptable limits for white and red wines. The organoleptic features of the samples were evaluated by a tasting panel of 7 oenologists. The sensory qualities of the variants were represented by radial diagrams using the method of principal characteristics. All samples had specific sensory profile, with a positive rating of the organoleptic criteria, according to the variety and the created experimental conditions for their making.