White wine bentonite fining

Minerals, particularly Bentonite, ate used to remove proteins that tend to cause haze in white wines. The natural tannin of ted wines usually removes unstable proteins from them. Excess tannin and related phenols can be removed and haze from them prevented by addition of proteins or adsorbents such as polyvinylpyttohdone. Addition of protein such as gelatin along with tannic acid can even be used to remove other proteins from white wines. Egg whites or albumen ate often used to fine ted wines. Casein can be used for either process, because it becomes insoluble in acidic solutions like wines. 

Duncan, B. (1992). Varietal differences in white grape protein Implications for bentonite fining. Aus. New Zealand Wine Ind.. 7,189-193. 

Fining is a winemaking technique used to enhance sensory or clarity properties of the wines. Common fining agents used with North Coast white wines are bentonite (a clay), casein (milk protein), gelatin (animal protein),... 

Protein levels in white wine have been reported by several authors and have been shown to differ by variety. Lee (1986) reported a range of protein concentration from 18 to 81 mg/L in 14 wines from different Australian regions and made from different varieties. Some of these wines appeared to have been fined with bentonite prior to analysis. Pocock et al. (1998) reported concentrations in unfined Australian wines up to several hundred mg/L. Hsu and Heatherbell (1987b) found a range of 19 4 mg/L in four different unfined white wines from Oregon, while a very large variation (20—260 mg/L) was noted by Bayly and Berg (1967). 

Pocock, K.F., Waters, EJ. (2006). Protein haze in bottled white wines how well do stability tests and bentonite fining trials predict haze formation during storage and transport . Aust. J. Grape Wine Res., 12, 212-220... 

In general, the effect of bentonite on red wines is comparable to that of protein fining. After flocculation and sedimentation, wines treated with doses of 25-40 g/hl of bentonite remain stable at low temperatures, staying brilliant and free of turbidity, even after several months. This treatment may be even more effective than gelatin (12 g/hl) or blood albumin (18 g/hl). It should, however, be taken into account that bentonite fixes anthocyanins, not only in discolored white wines but also in roses and young red wines. 

As bentonite flocculates in wine, with a behavior analogous to that of protein fining agents, experiments have been made in using it to clarify wine. In fact, its effectiveness in clarification depends on the type of bentonite and the composition of the wine. The only wines that may be properly clarified are reds or whites with low concentrations of polysaccharides and other protective colloids (Section 9.4.1), as these inhibit the flocculation and settling of the bentonite particles. In some winegrowing areas, bentonite is well suited to clarifying dry white wines, but elsewhere white wines may be more turbid after bentonite treatment than before. 

As noted previously, lysozyme complexes with and is partially inactivated by red wine phenolics and bentonite. In red wines, utilization may have an indirect sensory impact on palate structure similar to that of proteinaceous fining agents. In white wines, potential protein instability may result from its utilization. Thus, treated wines should be evaluated and treated with bentonite as appropriate. As of this writing, lysozyme is in the process of approval for winemaking purposes. 

Fining with casein, gelatin, or bentonite may be helpful in clarifying the must (Flanzy, 1998), especially when the grapes are botrytized, taking care to use small enough doses not to affect the flavor of the finished wine. Settling residues may be clarified in the same way as those from white must are clarified (Section 13.5.5). 

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