Influence of Native Saccharomyces cerevisiae Strains on Malvasia aromatica Wines.

BACKGROUND: In the search of tools to deal with climate change-related effects along with the aim of avoiding the loss of aromatic typicity in wine, two native yeasts strains of Saccharomyces cerevisiae (CLI 271 and CLI 889) were evaluated to determine their influence on white Malvasia aromatica wines aroma composition and sensory characteristics. METHODS: The strains were tested versus a commercial yeast strain (LSA). The fermentations were performed on grape must of the Malvasia aromatica variety previously macerated. Wine quality was studied by analysis of oenological parameters together with volatile aroma components using gas chromatography coupled to flame ionization detector (GC-FID) to quantify major volatiles compounds and headspace-solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) to determine terpenoids and C13-norisoprenoids. Sensorial analysis was also realized by an experienced taster panel. RESULTS: Wines from locally-selected yeasts strains used had lower volatile acidity levels and higher concentration of aromatic compounds compared to the commercial strain ones. The yeast strain S. cerevisiae CLI 271 provided wines with a higher concentration of esters related to fruity attributes, especially isoamyl acetate. The tasting panel highlighted the strong floral character of wines from S. cerevisiae CLI 889 fermentation. CONCLUSIONS: The use of microorganisms well adapted to climatic conditions can be used to produce quality wines of the Malvasia aromatica variety.

Quantification of Wine Mixtures with an Electronic Nose and a Human Panel.

In this work, an electronic nose and a human panel were used for the quantification of wines formed by binary mixtures of four white grape varieties and two varieties of red wines at different percentages (from 0 to 100% in 10% steps for the electronic nose and from 0 to 100% in 25% steps for the human panel). The wines were prepared using the traditional method with commercial yeasts. Both techniques were able to quantify the mixtures tested, but it is important to note that the technology of the electronic nose is faster, simpler, and more objective than the human panel. In addition, better results of quantification were also obtained using the electronic nose.

Effect of seasonal climate fluctuations on the evolution of glycoconjugates during the ripening period of grapevine cv. Muscat à petits grains blancs berries.

BACKGROUND: Temperature changes and rainfall fluctuations affect the winemaking industry by altering vine phenology, crop yield, must composition and wine quality. Here, the evolution of the varietal aroma potential during ripening over three consecutive seasons has been analyzed considering climate conditions. The effect of season, ripening date and climatic conditions on aroma precursor accumulation in grapes was studied by multivariate analysis and discussed in regard to the potential aromatic quality of the wine. RESULTS: In contrast to musts obtained from grapes harvested in warm and dry seasons (2014 and 2015), musts obtained from grapes harvested in the coolest and most humid year (2013) showed a lower pH, higher total acidity, higher varietal aroma potential index (IPAv), and higher aromatic potential of linalool, geraniol and nerol (typical of the Muscat flavor). CONCLUSION: Considering the three seasons, grapes synthesized and accumulated more precursors when milder temperatures and late rains throughout veraison were recorded. However, we observed a high fluctuation of aroma precursors during the ripening period, so choosing the correct harvesting date (according to grape aroma potential) may overcome some of the negative effects linked to climate conditions. © 2017 Society of Chemical Industry.

Yeast Monitoring of Wine Mixed or Sequential Fermentations Made by Native Strains from D.O. "Vinos de Madrid" Using Real-Time Quantitative PCR.

There is an increasing trend toward understanding the impact of non-Saccharomyces yeasts on the winemaking process. Although Saccharomyces cerevisiae is the predominant species at the end of fermentation, it has been recognized that the presence of non-Saccharomyces species during alcoholic fermentation can produce an improvement in the quality and complexity of the final wines. A previous work was developed for selecting the best combinations between S. cerevisiae and five non-Saccharomyces (Torulaspora delbrueckii, Schizosaccharomyces pombe, Candida stellata, Metschnikowia pulcherrima, and Lachancea thermotolorans) native yeast strains from D.O. "Vinos de Madrid" at the laboratory scale. The best inoculation strategies between S. cerevisiae and non-Saccharomyces strains were chosen to analyze, by real-time quantitative PCR (qPCR) combined with the use of specific primers, the dynamics of inoculated populations throughout the fermentation process at the pilot scale using the Malvar white grape variety. The efficiency of the qPCR system was verified independently of the samples matrix, founding the inoculated yeast species throughout alcoholic fermentation. Finally, we can validate the positive effect of selected co-cultures in the Malvar wine quality, highlighting the sequential cultures of T. delbrueckii CLI 918/S. cerevisiae CLI 889 and C. stellata CLI 920/S. cerevisiae CLI 889 and, mixed and sequential cultures of L. thermotolerans 9-6C combined with S. cerevisiae CLI 889.