TARTARIC STABILIZATION MAY AFFECT THE COLOR AND POLYPHENOLIC COMPOSITION OF TANNAT RED WINES FROM URUGUAY

Abstract

Tartrate precipitation affects the properties of wines, due to the formation of crystals that cause turbidity, even after being bottled. The forced tartaric stabilization is carried out frequently for young wines, through various physicochemical procedures. The traditional treatment for tartaric stabilization is refrigeration, but it can have a negative effect on wine’s sensory properties, and particularly on the color of red wines. The aim of this study was to evaluate the effect of different tartaric stabilization options on the color and phenolic composition of Tannat red wines from Uruguay. Cold treatment (C: 14 days at 4 ° C), mannoproteins (M: 100 mL / HL), arabic gum (AG: 200 g / HL), carboxymethylcellulose (CMC: 10 g / HL) and carboxymethylcellulose + arabic gum (AG CMC + 10 g / HL + 200 g / HL) were tested. The chromatic properties, basic composition, polyphenolic indexes, and anthocyanins and derived-anthocyanin pigments contents were analyzed. The initial impact of the cold treatment was significant, but differences with the other wines were attenuated over time. At 15 days of the start of the essay, C wine had significantly lower color intensity and was much brighter and less red than control wine. C had too the lowest anthocyanin and proanthocyanidin contents. Anthocyanin profile of this wine shows an increase in the proportion of non-acylated glucosides and malvidin, and a decrease in the percentages of delphinidin, cyanidin and coumaryl-glucosides. Anyway, the typical anthocyanin profile of the variety was slightly modified. All wines showed low differences in color and polyphenolic composition at five months from stabilization. However, the contents of free anthocyanins were decreased by all stabilization treatments in relation to the control wines. CMC+GA wines had the highest color intensity and proanthocyanidin levels while M and CMC wines had the highest catechin contents. At this time, it was verified that the contents of free anthocyanins were diminished by all treatments in relation to the control wine. At 14 months, CMC+GA wines had the highest colour intensity, and the lowest luminosity (L*). Colour intensities of C and CMC wines had not differences respect to those of control wines. However, all wines showed precipitation of tartaric salts at 5 and at 14 months from stabilization. Therefore, the tested options (products and doses) do not stabilize red wines adequately.