Environmental Conditions and Winemaking Decisions

Although a variety of LAB strains may exist in the vineyard, relatively few survive in wine, as previously noted. Reasons for this lie in individual and collective inhibitory roles played by environmental challenges, chief among which are pH, alcohol, nutrient availability, temperature, and SO2. 

Wine pH plays a pivitol role in determining which species will survive and develop, their growth rate as well as rate (and extent) of malate conversion, and its sensory outcome. In terms of initiation and completion of MLF, wines of pH 3.3 generally exhibit litde problem, whereas at lower pH, difficulty may be experienced (Kunkee, 1967). Leuc usually represents the dominant species in wine below pH 3.5. At higher pH, spoilage LAB, such as Lactobacillus and Pediococcus sp. (and Leuc oenos itself), may survive and grow as well. 

Malate conversion in wines at pH 3.6 produces more acetic acid (from utilization carbohydrates) than at a lower pH (Peynaud and Domercq, 1961 Zeeman et al., 1982 Giannakopoulos et al., 1984). Other types of spoilage, including production of objectionably high level of diacetyl, are also more likely to be seen in higher-pH wines undergoing MLF (Rankine et al., 1969). 

The time frame for MLF generally shortens as pH increases. Typical observations are those reported by Bousbouras and Kunkee (1971), who reported completion of MLF by Leuc. oenos (MLr34) in 164 days at pH 3.15, whereas at pH 3.83, completion required only 14 days. 

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