Wine Microbiology: Practical Applications and Procedures
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Winemaking from the vineyard to shipment of the bottled product is a series of challenges for winemaking staff. The introductory narrative of this book is designed to be an overview, from the wine microbiologist’s point of view, of those critical junctures in the process (CCPs) that are of concern in wine quality as well as intervention/control programs to address them. The second edition of Wine Microbiology builds upon the foundation of its highly successful predecessor with emphasis on modern molecular methods. It has been revised and updated with recent data and conclusions in all chapters.
Although Du Toit et al. (2005) suggested that a concentration of 0.8 mg/L molecular SO2 was needed to prevent the growth of Acetobacter pasteurianus, the authors further noted that this concentration did not completely eliminate the bacterium. Whereas some winemakers encourage non-Saccharomyces yeasts (Section 8.4), others desire to limit their growth due to synthesis of undesirable odors and ﬂavors. Although SO2 can suppress the non-Saccharomyces populations prior to alcoholic fermentation
of malolactic bacteria was suggested by Wibowo et al. (1988) who proposed that S. cerevisiae may inhibit O. oeni through the yeast production of antibacterial proteins/peptides. In support, Dick et al. (1992) isolated two proteins produced by S. cerevisiae that showed activity against O. oeni. Osborne (2005) was able to isolate a 96 6. Microbial Ecology During Viniﬁcation low-molecular-weight protein (3 to 6 kDa) that was inhibitory to O. oeni. Similar ﬁndings were reported by Comitini et al.
the particular amino acid, stage of growth, and activity of necessary transport enzymes, these amino acids may be (a) directly incorporated into proteins, (b) degraded for either their nitrogen or carbon components, or (c) stored in vacuoles or cytoplasm for later use (Bisson, 1991). Another “nutrient” important for yeast is the presence of oxygen. Without some initial oxygen, fermentation can slow because O2 is needed for sterol synthesis (Section 1.4.2). Owing to the activity of grape oxidases
expansion in the winery prior to inoculation. Media for preparing malolactic starter cultures frequently contain grape or apple juice supplemented with other nutrients like yeast extract, peptone, and Tween 80 (Pilone and Kunkee, 1972; Kunkee, 1974; Costello, 1988; Champagne et al., 1989; Krieger et al., 1990, 1993; Henick-Kling, 1993). One preculture method is to inoculate pH adjusted (4.5) grape juice that has been diluted 1 : 1 with water and contains 0.5% w/v yeast extract. Once the culture
3,5 Hexadiene-2-ol Ethanol CH 2 =CH-CH=CH-CH-CH3 OCH2 CH 3 2-Ethoxyhexa-3,5-diene Figure 11.5. Microbiological formation of “geranium” odor or tone. confused with geraniol, a monoterpene important for the odor of some grape cultivars. Edinger and Splittstoesser (1986) reported that all strains of O. oeni studied reduced sorbic acid to sorbic alcohol but noted that strains of Pediococcus and Lactobacillus could not. Based on these ﬁndings, winemakers wishing to stabilize juice with sorbate for