Aim: Among the most important factors influencing wine quality are yeast strains and fermentation temperature. Fermentation at low temperature is presently used in winemaking to improve both aroma formation and retention. In this study, we have analysed the oenological characteristics of Tempranillo wines produced at 12 and 28°C by different Saccharomyces species and hybrids. Methods and Results: Low temperature had a strong influence on yeasts fermentation kinetics, increasing fermentation times to more than 2 weeks. In some strains, glycerol production seemed to be positively influenced by low fermentation temperature. Analysis of the aroma composition of wines produced by different Saccharomyces species and hybrids revealed large differences depending on fermentation temperature. Conclusions: Higher alcohols production seemed to be dependent on the strain. Production of acetate esters seemed to be favoured at 28°C, whereas production of ethyl esters was apparently preferred at low fermentation temperatures. The best aroma producers at 28°C were Saccharomyces cerevisiae strains, whereas Saccharomyces uvarum and some hybrids excelled at 12°C. Significance and Impact of the Study: Our results suggest that fermentation temperature and yeast species are of crucial importance for production of metabolites influencing wine aroma.

Yeasts with a high fructose consumption capability are very important for winemakers to solve problems associated with sluggish or stuck fermentations causing undesirable sweetness in wines. In the present study, we analyze the kinetics of glucose and fructose consumption during wine fermentations performed at low (12 degrees C) and high (28 degrees C) temperatures by twelve different yeast strains belonging to the species Saccharomyces cerevisiae, S. bayanus var. uvarum, S. kudriavzevii as well as interspecific Saccharomyces hybrids. Different mathematical equations (sigmoid, exponential and linear decay functions) were used to fit, by means of linear and nonlinear regressions, the sugar degradation along the fermentative process. Temperature had an important influence on glucose and fructose consumption, and clearly different degradation profiles were observed at 12 and 28 degrees C. From the obtained equations, times to consume half and total of the initial glucose and fructose concentrations present in the must were calculated, allowing a quantitative comparison among yeasts in order to select the fastest fermentative yeast according to the fermentation temperature. In general, all yeasts assayed showed a slightly higher preference for glucose than fructose at both temperatures, confirming the glucophilic character of Saccharomyces wine yeasts. However, at low temperatures, some Saccharomyces yeasts showed a fructophilic character at the beginning of fermentation. This kind of studies can be very useful for the wine industry to select yeast strains with different glucose/fructose preferences.

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Higher alcohols and acetate esters are important flavour and aroma components in the food industry. In alcoholic beverages these compounds are produced by yeast during fermentation. Although Saccharomyces cerevisiae is one of the most extensively used species, other species of the Saccharomyces genus have become common in fermentation processes. This study analyses and compares the production of higher alcohols and acetate esters from their amino acidic precursors in three Saccharomyces species: Saccharomyces kudriavzevii, Saccharomyces uvarum and S. cerevisiae. The global volatile compound analysis revealed that S. kudriavzevii produced large amounts of higher alcohols, whereas S. uvarum excelled in the production of acetate esters. Particularly from phenylalanine, S. uvarum produced the largest amounts of 2-phenylethyl acetate, while S. kudriavzevii obtained the greatest 2-phenylethanol formation from this precursor. The present data indicate differences in the amino acid metabolism and subsequent production of flavour-active higher alcohols and acetate esters among the closely related Saccharomyces species. This knowledge will prove useful for developing new enhanced processes in fragrance, flavour, and food industries.

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