Re: how does temperature affect fruit fermentation?

How does temperature affect fruit fermentation?

There are many fermented drinks made from fruit. These include drinks made from bananas, grapes and other fruit. Grape wine is perhaps the most economically important fruit juice alcohol. It is of major economic importance in Chile, Argentina, South Africa, Georgia, Morocco and Algeria. Alcoholic fruit drinks are made from many other fruits including dates in North Africa, pineapples in Latin America and jack fruits in Asia.

Temperature plays a major role in any fermentation process. It is one of the important parameters that can affect the fermentation process and final quality of product. Temperature has an impact on the growth and enzyme activity of different strains of microbial cultures used in fermentation. In case of wine, at temperatures of 10 to 15° C, the non-Saccharomyces species have an increased tolerance to alcohol and therefore have the potential to contribute to the fermentation. Ethanol decreases with increasing fermentation temperature. 2,3-butanediol increases with increasing temperature of fermentation. Acetoin also increases greatly at the higher fermentation temperatures. Other impurities also vary depending upon the temperature.

The traditional fermentation process uses Saccharomyces cerevisiae or natural yeast present on fruit. Presently many bacterial cultures are used in the fermentation process. Yeasts are active in a very broad temperature range - from 0 to 50° C, with an optimum temperature range of 20 to 30° C. The temperature of fermentation is usually from 25 to 30° C, and the duration of the fermentation process may extend from a few days to two weeks. Red wines are fermented at 20 to 30º C for about seven days. This higher temperature is necessary to extract the pigment from the grape skins.

White wines are fermented at low temperature, and slow fermentation favours the retention of volatile compounds. This approach produces a wine of generally expected taste and quality. During storage, wines are prone to non-desirable microbial changes. Yeasts, lactic acid bacteria, acetic acid bacteria and fungi can all spoil or taint wines after the fermentation process is completed. This can be controlled by favorable temperature conditions for preservation and enzyme activity. Temperature should be controlled, since alcohol content vaporizes at a temperature of 75 to 78° C.

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References:

http://www.ajevonline.org/cgi/content/abstract/18/3/157

http://www.fao.org/docrep/x0560e/x0560e08.htm