Abstract
The alcohol content in wine has increased due to external factors in recent decades. In recent reports, some non-Saccharomyces yeast species have been confirmed to reduce ethanol during the alcoholic fermentation process. Thus, an efficient screening of non-Saccharomyces yeasts with low ethanol yield is required due to the broad diversity of these yeasts. In this study, we proposed a rapid method for selecting strains with a low ethanol yield from forty-five non-Saccharomyces yeasts belonging to eighteen species. Single fermentations were carried out for this rapid selection. Then, sequential fermentations in synthetic and natural must were conducted with the selected strains to confirm their capacity to reduce ethanol compared with that of Saccharomyces cerevisiae. The results showed that ten non-Saccharomyces strains were able to reduce the ethanol content, namely, Hanseniaspora uvarum (2), Issatchenkia terricola (1), Metschnikowia pulcherrima (2), Lachancea thermotolerans (1), Saccharomycodes ludwigii (1), Torulaspora delbrueckii (2), and Zygosaccharomyces bailii (1). Compared with S. cerevisiae, the ethanol reduction of the selected strains ranged from 0.29 to 1.39% (v/v). Sequential inoculations of M. pulcherrima (Mp51 and Mp FA) and S. cerevisiae reduced the highest concentration of ethanol by 1.17 to 1.39% (v/v) in synthetic or natural must. Second, sequential fermentations with Z. bailii (Zb43) and T. delbrueckii (Td Pt) performed in natural must yielded ethanol reductions of 1.02 and 0.84% (v/v), respectively.
Highlights
Global climate change has caused an increase in the alcohol content of wines in recent decades [1,2,3]
These strains belonged to the species Hanseniaspora uvarum (2), Issatchenkia terricola (1), Lachancea thermotolerans (2), Metschnikowia pulcherrima (2), Saccharomycodes ludwigii (1), Starmerella bacillaris (1), Torulaspora delbrueckii (3), and Zygosaccharomyces bailii (2)
We focused on the selection of non-Saccharomyces yeasts with low ethanol yield by performing two short-term trials in 5 days
Summary
Global climate change has caused an increase in the alcohol content of wines in recent decades [1,2,3]. If grapes are harvested when phenolic compounds are mature, the grape must will have high concentration of sugars and low acidity, which produces wines with a high ethanol content. If the harvest occurs before that point, when sugar accumulation and pH are appropriate, wines will present a reduction in several characteristics (aroma, taste, and astringency) due to insufficient phenolic maturation. A high concentration of ethanol may lead to sluggish and stuck fermentations [4,5,6]. It can break the balance among acids, sugars, and tannins and develop unpleasant characteristics due to the enhancement of bitterness and burning sensation during tasting [7]. There are other reasons to achieve a lower ethanol content in wines, from their reduction in aromatic profile to the tax increase that will impact the final price of wines
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