Tartrate Stabilization by the Contact Process

Abstract

Studies and observations in conjunction with reverse osmosis for tartrate stabilization indicated that the precipitation rate for potassium bitartrate (KHT) at a given temperature is predominantly a function of the quantity of KHT in solution above the saturation level. Precipitation can be greatly accelerated by increasing the concentration or by adding crystalline KHT. Found very suitable for monitoring KHT precipitation were conductivity measurements. KHT crystals are formed in two concentration-related phases: an induction phase to develop nuclei; and a crystallization phase. Adding crystalline KHT reduces the time factor since nuclei need not be induced. Further studies involved the theoretical KHT crystallization mechanism and the correlations between added KHT quantities as well as crystal size and precipitation rate. Tartrate stability is attained by chilling the wine to a desirable stability temperature well above conventional coldstabilizing temperatures, followed by KHT addition and holding for about 90 minutes. The KHT crystals removed can be used again, although they must be subjected to periodic or partial wet grinding in a bypass arrangement.

The contact or seeding process can be carried out on a small scale by simple sedimentation, or on a large scale in which the crystals are separated with the aid of special filters.

The analytical data indicate that it is now possible to determine whether a wine is tartrate stable by using the tables elaborated by Berg and Keefer (1) and by additionally calculating the activity product and the relative supersaturation.