OTHER WINE-ASSOCIATED BACTERIA

The genus Bacillus is comprised of aerobic (catalase positive) endospore-producing Gram-positive bacteria. The bacilli are primarily soil-borne or- 

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We realize that there are a number of factors in addition to temperature that influence the % alcohol response of the wine sugar content, pressure, magnesium concentration in the fruit, phosphate concentration in the fruit, presence of natural bacteria, etc. Although we strive to keep as many of these factors as controlled and therefore as constant as we can (e.g., pressure), we have no control over many of the other factors, especially those associated with the fruit (see Section 1.2). However, even though we do not have control over these factors, it is nonetheless reasonable to expect that whatever the % alcohol response is at 23°C, the % alcohol response at 27°C should increase for each of the fruits in our study if temperature has a significant effect. That is, if we are willing to make the assumption that there are no interactions between the factor of interest to us (temperature) and the other factors that influence the system, the differences in responses at 27°C and 23°C should be about the same for each pair of experiments carried out on the same fruit. 

As well as fruity and buttery aromas, MLF has also been associated with other characteristic aromas such as floral, roasted, vanilla, sweet, woody, smoked, bitter, honey, etc. (Flenick-Kling 1993 Sauvageot and Vivier 1997). However, further studies are required to be able to relate the wine characteristics that are modified during malolactic fermentation with the production and/or degradation of a specific chemical compound by wine lactic acid bacteria. With this information, the winemaker can choose the best strain of lactic acid bacteria to obtain wine with a specific aroma or flavour. 

Bertrand, 1994 Allen, 1995) decanal and ( )-2-nonenal, on the other hand, are associated with sawdust or plank odour (Chatonnet and Dubourdieu, 1996 1998). The principal carbonyl compound formed in MLF is 2,3-butanedione (diacetyl), whose level can improve, or affect, the wine with its butter-like or fat note (Davis et al., 1985). Diacetyl and 3-hydroxy-2-butanone (acetoin, the reduced form of diacetyl) are produced by pyruvate metabolism of yeasts and lactic bacteria, and their levels may increase two or three fold with MLF depending on the lactic bacteria strain involved (Davis et al., 1985 Martineau and Henick-Kling, 1995 Radler, 1962 Fornachon and Lloyd, 1965 Rankine et al., 1969 Mascarenhas, 1984). For diacetyl in wine sensory thresholds ranging from 0.2mg/L (in Cbardonnay) to 0.9mg/L (Pinot noir), and 2.8 mg/L (Cabernet Sauvignon wine), are reported (Martineau et al., 1995). 

Bacteria are not affected by sorbic acid, and, in fact, several species can metabolize the acid to eventually yield 2-ethoxyhexa-3,5-diene, a compound that imparts a distinctive geranium odor/tone to wines (Section 11.3.5). Other odor/flavor-active compounds detected in spoiled wines treated with sorbic acid include l-ethoxyhexa-2,4-diene and ethyl sorbate (Chisholm and Samuels, 1992), the latter of which has been associated with off-flavors in sparkling wines (De Rosa et al., 1983). Whereas Chisholm and Samuels (1992) described ethyl sorbate as possessing a honey or apple aroma, De Rosa et al. (1983) thought the compound imparted a very unpleasant pineapple-celery odor upon short-term (6 month) storage. Based on this observation, De Rosa et al. (1983) recommended that sorbates should not be used in sparkling wine production. 

Additional yeast spoilage is induced by species of the genera Candida Mycoderma), Pischia and Hansenula (Willia). Other microorganisms are involved in the formation of viscous, moldy and ropy wine flavor defects. Bacterial spoilage may involve acetic acid and lactic acid bacteria. In this case vinegar or lactic acid souring is detectable. It has usually been associated with mannitol fermentation which may result in considerable amounts of mannitol. 

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