Validation of a Standard Protocol to Assess the Fermentative and Chemical Properties of Saccharomyces cerevisiae Wine Strains

Abstract

This paper reports on a common experiment performed by 17 Research Units of the Italian Group of Microbiology of Vine and Wine (GMVV), which belongs to the Scientific Society SIMTREA, with the aim to validate a protocol for the characterization of wine strains of Saccharomyces cerevisiae. For this purpose, two commercial S. cerevisiae strains (EC 1118 and AWRI796) were used to carry out inter-laboratory-scale comparative fermentations using both synthetic medium and grape musts and applying the same protocol to obtain reproducible, replicable, and statistically valid results. Ethanol yield, production of acetic acid, glycerol, higher alcohols, and other volatile compounds were assessed. Moreover, the Fourier transform infrared spectroscopy was also applied to define the metabolomic fingerprint of yeast cells from each experimental trial. Data were standardized as unit of compounds or yield per gram of sugar (glucose and fructose) consumed throughout fermentation, and analyzed through parametric and non-parametric tests, and multivariate approaches (cluster analysis, two-way joining, and principal component analysis). The results of experiments carried out by using synthetic must showed that it was possible to gain comparable results from three different laboratories by using the same strains. Then, the use of the standardized protocol on different grape musts allowed pointing out the goodness and the reproducibility of the method; it showed the main traits of the two yeast strains and allowed reducing variability amongst independent batches (biological replicates) to acceptable levels. In conclusion, the findings of this collaborative study contributed to the validation of a protocol in a specific synthetic medium and in grape must and showed how data should be treated to gain reproducible and robust results, which could allow direct comparison of the experimental data obtained during the characterization of wine yeasts carried out by different research laboratories.

Role of Yeasts on the Sensory Component of Wines

“…The PCA plot revealed that the wines obtained from the same must fermented by the thirty different indigenous strains differed significantly in terms of their aromatic profile as they were located in different quadrants. This result confirms the effective impact of yeast strains on the aroma properties of the wines produced, starting from the same grape must [48].…”

“…The PCA plot revealed that the wines obtained from the same must fermented by the thirty different indigenous strains differed significantly in terms of their aromatic profile as they were located in different quadrants. This result confirms the effective impact of yeast strains on the aroma properties of the wines produced, starting from the same grape must [48]. In this perspective, the selection of new S. cerevisiae strains, able to impart specific sensorial and aromatic features, could be a useful tool to increase the gamma of products present on the market.…”

“…The variability in the formation of volatile compounds during grape must fermentation depends on several factors, including, in particular, the inoculated yeasts, which, transforming the precursors initially present in the must, determine the final organoleptic characteristics of the wine [47]. Recently, a study has reported that wines obtained by different research units, using the same S. cerevisiae strains, were generally characterized by different qualitatively volatile molecule profiles in relation to the must employed but also in the function of the inoculated strain [48].…”

The Riboflavin Metabolism in Four Saccharomyces cerevisiae Wine Strains: Assessment in Oenological Condition and Potential Implications with the Light-Struck Taste

“…Two laboratory growth media were prepared on the base of synthetic grape must composition (SM; glucose 115 g/L, fructose 115 g/L, tartaric acid 5 g/L, malic acid 3 g/L, citric acid 0.2 g/L, l -arginine 2 g/L, pH = 3.5) [ 30 , 31 ], modified as follow: (i) SMV, not containing RF, supplemented with essential vitamins and salts for yeast growth as described in Verduyn et al 1992 [ 32 ]; (ii) SMV containing 125 µg/L RF (SMV+RF). Concentrated stock solutions of each additional compound were prepared, filtered through 0.22 μm nitrocellulose membranes (Millipore filter, type GSWP, Billerica, MA, USA) and added in adequate amounts.…”

Impact of Two Commercial S. cerevisiae Strains on the Aroma Profiles of Different Regional Musts

“…The differential impact of two commercial S. cerevisiae wine strains, EC1118 and AWRI796, commonly known among oenologists and yeast producers, was assessed on the aroma profile of five different regional grape musts. To limit the variables in the fermentation process and obtain more reliable results, interlaboratory scale comparative fermentations of five different regional red grape musts were carried out by five different research units (Rus) under identical conditions and following the same protocol during the entire process [38].…”