Effects of fermentation temperature on the strain population of Saccharomyces cerevisiae Ma. Jesu ´s Torija, Nicolas Roze `s, Montse Poblet, Jose ´ Manuel Guillamo ´n, Albert Mas * Unitat d’Enologia del Centre de Refere `ncia de Tecnologia d’Aliments, Dept Bioquı ´mica i Biotecnologia, Facultat d’Enologia de Tarragona, Universitat Rovira i Virgili, Ramo ´n y Cajal, 70, 43005 Tarragona, Spain Received 9 July 2001; received in revised form 2 December 2001; accepted 3 March 2002 Abstract The influence of fermentation temperature (from 15 to 35 jC) on a mixed strain population was studied. Mitochondrial DNA analysis was used to differentiate Saccharomyces cerevisiae strains and the frequency of each strain during the alcoholic fermentation was determined. The chemical analyses of resulting wines were carried out. The temperature determined how Saccharomyces strains developed and how effectively they fermented. Some strains performed better at high temperatures and others at low temperatures. The maximal population size was similar at all temperatures. At low temperatures, however, it was reached later though it remained constant throughout the alcoholic fermentation. On the other hand, viable cells decreased at high temperatures, especially at 35 jC. Obviously, the composition of the wines changed as the temperature of fermentation changed. At low temperatures, alcohol yield was higher. Secondary metabolites to alcoholic fermentation increased as the temperature increased. Glycerol levels were directly affected by temperature. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Glycerol; Ethanol; Yeast; Population dynamics; Wine 1. Introduction Alcoholic fermentation is a combination of com- plex interactions involving must variety, microbiota and winemaking technology. Obviously, some factors strongly affect alcoholic fermentation, and as a con- sequence, the quality of the wine. The most important ones are the clarification of grape juice, the levels of the sulphur dioxide, the temperature of fermentation, the composition of the grape juice, inoculation with selected yeasts and the interaction with other micro- organisms (Ribe ´reau-Gayon et al., 2000). One of these factors, the temperature of fermentation, directly affects the microbial ecology of the grape must and the biochemical reactions of the yeasts (Fleet and Heard, 1993). Several authors have suggested that some species of non-Saccharomyces have a better chance of grow- ing at low temperatures than Saccharomyces (Sharf and Margalith, 1983; Heard and Fleet, 1988) because they can increase their tolerance to ethanol (Gao and 0168-1605/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0168-1605(02)00144-7 * Corresponding author. Tel.: +34-977-250000; fax: +34-977- 250347. E-mail address: amb@fe.urv.es (A. Mas). www.elsevier.com/locate/ijfoodmicro International Journal of Food Microbiology 80 (2002) 47 – 53