Fungal diversity during fermentation correlates with thiol concentration in wine

Abstract

Background and Aims: Agricultural products deriving from the same genotypic clone often have different physical and sensory properties that influence their overall quality and value. Microorganisms may play key roles throughout the production of many crops, affecting plant and fruit health and modifying plant materials to produce socially and economically important commodities. Following this idea, we investigated whether fungal diversity both prior to and during fermentation was correlated with the concentration of three volatile thiols important to Sauvignon Blanc aroma and flavour. Methods and Results: We used molecular and metagenomics approaches to quantify yeast populations and GC/MS to quantify thiols and analysed these using random forest statistical approaches. The species of Saccharomyces yeasts present at the end of fermentation are significantly correlated with the concentration of 4-mercapto-4-methylpentan-2-one, while several other fungal species present in the must, which are known to be associated with vine and fruit health, are also correlated with thiol concentration. Conclusions: These data highlight the relationship between the presence of Saccharomyces uvarum and the production of 4-mercapto-4-methylpentan-2-one, while some members of the fungal community correlate with thiol concentration generally. Thus, components of the fungal community may potentially affect the accumulation of odourless precursors in grape via pathogenic effects during fruit ripening, but further research is required to confirm such speculation. Significance of the Study: This work emphasises the need for a better understanding of the interactions between microbial populations and agricultural products, and has implications for the management of fungal diversity and disease in these systems.

The molecular biology of fruity and floral aromas in beer and other alcoholic beverages

“…This observation is consistent with the finding that an S. uvarum strain produces high levels of thiols compared to S. cerevisiae wine strains (Knight et al. 2018). The level of subtelomeric silencing may therefore play an important role in interspecies hybrids, such as S. pastorianus .…”

Taxonomic and Functional Characterization of the Microbial Community During Spontaneous in vitro Fermentation of Riesling Must

“…For example, we found that several Saccharomyces species besides S. cerevisiae were mapped in our data, namely, Saccharomyces paradoxus and Saccharomyces pastorianus (Supplementary Table S4B). Since previous studies have reported that S. paradoxus is rarely found in wine fermentations (Sicard and Legras, 2011; Knight et al, 2018), and there is a close evolutionary relationship between S. cerevisiae and S. paradoxus (Borneman and Pretorius, 2015), it is possible that our mapping to S. paradoxus is an artifact driven by close sequence homology (Naumova et al, 2005). In order to overcome the database problems, we applied functional analysis and binning strategies to metagenomic data, to make the results less dependent on only a single database.…”

Analytical impact of Metschnikowia pulcherrima in the volatile profile of Verdejo white wines

“…In recent years, some studies have determined the contribution of particular non-Saccharomyces yeasts to wine composition, showing that some strains can be used to improve thiol concentration in wines. Furthermore, Knight et al (2018) suggest that the yeast diversity in spontaneous wine fermentations can be directly correlated with the final thiol concentrations in wine, highlighting the contribution of Saccharomyces uvarum strains on it.…”