Must clarification

Removing sediment from white grape must clarification is excellent. It may even be excessive, leading to difficulties during fermentation. The technical and economic advantages of this technique have not been clearly demonstrated. 

Each QP program must include descriptions (criteria) at each step for acceptable fruit quality (sugar concentrations, titratable acidity, microbial contamination, etc.), SOg additions (when and how much), press times and pressures, must clarification procedures, yeast inoculation rates, concen-... 

Ferrando, M., C. Guell, and F. Lopez. 1998. Industrial wine making comparison of must clarification treatments. / Agric. Food Chem. 46 1523-1528. 

Williams, J.T., C.S. Ouch, and H.W. Berg. 1978. White wine composition and quality as influenced by method of must clarification. Am. J. Enol. Vitic. 29 92-96. 

In dry white and rose winemaking, excessive must clarification can also lead to the excessive production of volatile acidity by yeast. This phenomenon can be particularly pronounced with certain yeast strains. Therefore, must turbidity should be adjusted to the lowest possible level which permits a complete and rapid fermentation (Chapter 13). Solids sedimentation (must lees) furnishes long-chain unsaturated fatty acids (C18 l, C18 2). Yeast lipidic alimentation greatly... 

Must clarification before the initiation of fermentation has long been known to affect the quality... 

Must clarification also affects fermentation phenomena. It eliminates some of the wild yeasts, along with the natural vegetal sediment, but inoculation compensates for this loss, and is also often recommended to compensate for the small population present at the time of filling the tank. In this manner, fermentation is carried out by selected strains that best express must quality, without the development of olfactory flaws. 

Table 3.15. Analysis of the effect of different must clarification operations on fermentability loss (Rib eau-Gayon et al., 1975b)...

Must lees particles and even glucidic macromolecules, making up part of the colloidal turbidity of musts such as yeast hulls, can adsorb short-chain fatty acids (C8 and CIO) (Section 3.6.2) (Ollivier et al., 1987). In consequence, the level of must clarification should be controlled for each type of white winemaking by measuring must cloudiness or turbidity, expressed in NTU... 

Pre-fermentation practices at the winery destroy the structure of grape cells. Enzymes are placed in direct contact with abundant substrates, resulting in explosive enzymatic reactions. Laccase activity is the best-known reaction secreted by B. cinerea, it alters phenolic compounds in the presence of a sufficient amount of oxygen. Not all of the enzymes present are harmful to quality—pectinolytic enzymes, for example, favor must clarification by parietal constituent hydrolysis. For several years, enologists have sought to amplify these favorable reactions in using more active, industrially produced enzymes. 

In white winemaking, this deacidification should be effected after must clarification but before fermentation. Aromatic ester production by yeasts is facilitated by a moderate pH. Conversely, this treatment permits a more precise deacidification of red wines when performed at the end of alcoholic fermentation, at the time of running off. It can also help to trigger malolactic fermentation. 

Table 13.13. Influence of must clarification on Ce alcohols concentrations (hexanol - - hexenols) in wine (Dubourdieu et al., 1980)...

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