Sulfur dioxide, winemakers

During traditional winemaking in October, endogenous yeasts are very active and their action may need to be limited by appropriate additions of sulfur dioxide. Usually spontaneous fermentation begins with apiculate yeasts of the genus Hanseniaspora. However, their extended... 

Finally, as Martini and Martini (5) note, the selective pressures at work in the winery environment may influence the survivability of the indigenous yeasts with respect to ethanol or sulfur dioxide tolerance it is not clear, however, how such environmental pressures would be selecting for desired flavor production. Certainly few winemakers completely sterilize their wineries and scorch their vineyards when they obtain a wine with less than optimal flavor attributes ... 

In many countries, alcoholic fermentation is induced by inoculation with a yeast starter culture of Saccharomyces selected for its desirable winemaking qualities (Kunkee, 1984 Kunkee and Bisson, 1993 Rainieri and Pretorius, 2000 Reed and Chen, 1978 Reed and Nagodawithana, 1988). Starter cultures of S. cerevisiae strains are generally used because of to their increased ethanol and sulfur dioxide resistance and production of desirable aromas and flavors (Boulton et al., 1996 Ebeler, 2001 Nykanen, 1986 Reed and Chen, 1978 Reed and Nagodawithana, 1988). 

Edinger, W.D. 1986. Reducing the use of sulfur dioxide in winemaking. Part I. Vine. Wine. Manage 12, 24-27. 

Sugar molecules are predictably reactive due to their polyfunctional character, especially the presence of a carbonyl, aldehyde or ketone radical. A certain number of these reactions play a role in winemaking, especially in assaying sugar levels in wine. Addition reactions with sulfur dioxide are described elsewhere (Volume 1, Sections 8.3.2 and 8.4.4). 

This technique is particularly efficient when filtration may not be used directly, especially in white winemaking. It is a rapid method for obtaining wines that are clean, stable and ready to drink, without adding excessive amounts of sulfur dioxide. It also minimizes losses of lees wine, which... 

Hydrogen ion concentration plays a major role in the activity of various antimicrobial agents used in winemaking. As previously discussed and as seen in Figs 1.8, the percentage of molecular sulfur dioxide, increases with decreasing pH. This relationship also applies in the cases of sorbic and benzoic acids. 

The fermentation process can be artificially controlled and impeded by the addition of sulfur dioxide or potassium metabisulfite. The addition of this preservative poses a potential health hazard. The residual sulfites present in wine have been known to elicit urticaria, asthmatic reactions and respiratory failure. In the United States, since 1987, warning labels indicating the presence of sulfites must appear on wine bottles containing at least 10 ppm of sulfites (Fisher 1997)- In addition to their importance in wine making, sulfur dioxide and sulfites are used as food additives for their antimicrobial effect. Contact dermatitis to potassium metabisulfite has developed in a pharmaceutical worker (Nater 1968) and may also occur in bakers, from occupational exposure to flour (Apetato and Marques 1986), and in hairdressers to permanent wave solution, but has not been reported in winemakers. Sulfur dioxide has also been reported to cause contact urticaria (Maibach and Johnson 1975). 

Occupational dermatitis in winemakers must be a rare event in fact, no cases have been reported. With the exception of sulfur dioxide, very few chemicals are added during vinification. Juice and must failing to... 

Hood, A. (1983) Inhibition of growth of wine lactic-acid bacteria by acetaldehyde-bound sulfur dioxide. Aust. Grapegrower and Winemaker 232, 34-43. 

Presented here are general descriptions of preservatives and sterilants as well as filtration options that can be used at different stages during the winemaking process. A variety of additives may be used to control the growth of microorganisms. These include sulfur dioxide, lysozyme, dimethyl dicarbonate, and sorbic acid. The use of other additives such as fumaric acid, nisin, carbon monoxide, and particular plant extracts has also been explored. Additional antimicrobial chemicals that are used in a winery as sanitizers are discussed in Chapter 9. 

Sulfur dioxide is widely recognized in both the wine and food industries for its antioxidative and antimicrobial properties. The current legal limit for SO2 in wines in the United States is 350 mg/L, a concentration well above levels normally used by winemakers. Nevertheless, wines that contain greater than 10 mg/L must disclose this information on the label. Because SO2 is a metabolite of yeasts during fermentation (Section 1.5.2), wines will usually contain some sulfite even though additions were not made during processing. 

Chemical hazards also pose a concern for winemakers. These can be divided into naturally occurring, intentionally added, and unintentional/ incidental. Examples of naturally occurring chemicals that could pose a risk to human health are biogenic amines (Section 11.3.6), ethyl carbamate (11.3.2), and mycotoxins (Section 4.5.2). Intentionally added chemicals include sulfur dioxide (gas, sulfur wicks, or potassium metabisulfite), tartaric acid, Velcorin (Section 5.2.2), and microbial nutrient formulations (diammonium phosphate or proprietary blends). Finally, uninten-tional/incidental chemicals would include residues of agricultural chemicals that exceed approved levels, cleaners or sanitizers (Chapter 9), and the inadvertent transfer of lubricants from equipment. 

Sorbate has also been implicated as the precursor of a flavor defect in wine that has a geranium character. Sorbate may be added in the winemaking process as a secondary yeast inhibitor to reduce the amount of sulfur dioxide used. While sorbate is a good yeast inhibitor, it does not inhibit the growth of bacteria. Crowell and Guymon [144] have found that certain bacteria in wines can convert sorbate to 2-ethoxyhexa-3,5-diene, which has a geranium character. 

The addition of 20-30 mg/1 ascorbic acid prevents the formation of colloidal turbidity (called chill haze) in beer, and also prevents adverse changes in flavour due to the oxidation that occurs during pasteurisation and storage. The use of ascorbic acid in winemaking can reduce the amount of sulfur dioxide used for fumigation. 

The addition of thiamine is legal in several countries (EU, at a dose of 50 mg/hl) but it is rarely used to accelerate fermentation in winemaking. It effectively decreases significant ketonic acid concentrations by decarboxylation (pyruvic and a-ketoglutaric acid). Large quantities of these acids bind to sulfur dioxide in botrytized sweet wines (Section 8.4.2). 

The general use of sulfur dioxide (SO2) appears to date back to the end of the 18th century. Its many properties make it an indispensable aid in winemaking. Perhaps some wines could be made in total or near-total absence of SO2 but it would certainly be presumptuous to claim that all of the wines produced in the various wineries throughout the world could be made in this manner. It must also be taken into account that yeasts produce small quantities of SO2 during fermentation. In... 

Its various properties can make sulfur dioxide seem indispensable in winemaking. The goal of enology is not to eliminate this substance completely but rather to establish responsible... 

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