Use of mathematical laws for optimizing the doses of swelled and dry bentonite during the fining of white wines. Part I: clarification and colloidal stability

Abstract

White wine clarity is of prime importance for the winemaker as a bottle showing haziness is likely to be rejected by the consumer. It is then important to ensure a perfect colloidal stability to the wine. This study concerns a Sauvignon white wine from the Touraine area (vintage 2000). We have determined the relationships existing between the dose of bentonite used, the manner for preparing the bentonite (the dry cristalites can be directly introduced in the wine; the bentonite can also be used after swelling in water), the decrease of wine protein haze and clarifying efficiency. Clarifying kinetics are identical for 10 g/hl swelled bentonite (SB) and 100 g/hl dry bentonite (DB). The difference of efficiency between SB and DB is all the more marked than the dose used increases. At the end of the kinetics, for identical treatments (the doses are between 10 and 100 g/hl), wines fined with DB have turbidity 2-3 times higher than the same wines fined with the same doses of SB. The mathematical law shows that the turbidity decreases by 17 % when the dose of dry bentonite is doubled. For this example, the relationship between these two parameters follows a power law. The decrease reaches 27 % when the wine is fined with SB. According to heat treatment, the wine must be treated with 30 g/hl SB and 60 g/hl DB to present a good colloidal stability. For this Sauvignon wine, fined with SB, haze risk decreases by 82 % each time the dose of bentonite increases by 10 g/hl. In this case, the relationship between these two parameters follows an exponential law. If an addition of oak tannins is made in the wine fined with 30 g/hl SB or 60 g/hl DB, any trouble appears. For heat treatment test and tannin addition test, the ratio is each time 2 DB for 1 SB to have a correctly fined wine. On the basis of these results, the use of dry bentonite seems to be less interesting than the use of swelled bentonite.