Effetto della matrice colloidale sulla stabilità tartarica dei vini

[Autom. eng. transl.] Tartaric acid is an organic acid naturally present in grapes and is found in must and wine in the form of potassium salt, calcium or as potassium hydrochlorate. Of these possible forms, the most abundant is that of potassium bitartrate which, as is known, has reduced solubility in alcoholic medium and, therefore, is susceptible to precipitation, with the formation of a salt deposit on the bottom of the bottle. Far from being positively perceived by the consumer, this natural aspect of wine is tackled in the phases prior to bottling, with techniques of crystallization induced in both continuous and discontinuous systems. This article reports the results and conclusions of a recent study aimed at understanding the role played by some elements of the wine matrix on tartaric precipitation mechanisms. The protective role of wine colloids on tartaric stability has long been known and is the main reason why fining treatments are conducted in the phase preceding the actual tartaric stabilization. However, there is little information on the relationships of the individual colloidal components of wine with potassium bitartrate. From the results gathered, it is clear that the quantitative relationship between proteins and tannins, in addition to influencing the organization of colloids in the solution, has a direct influence on the capacity of potassium bitartrate crystals to increase, to an extent and according to different mechanisms.