Abstract
In winemaking, non-Saccharomyces yeast species contribute important organoleptic complexity. Current interest focuses on abundant and dominant strains characteristically present in the early phase of spontaneous alcoholic fermentations. Non-Saccharomyces species are particularly relevant in Port wine production such that the fermentation is prematurely stopped, after the metabolism of only one half of the available sugar, through fortification with aguardente. This work aimed to isolate, identify and characterize non-Saccharomyces species present in spontaneously fermenting Port. To accomplish these goals, yeasts were isolated from a selection of frozen must samples (2012–2016 harvests), using a pre-screening process choosing only the best candidates based on the organoleptic quality of the corresponding fortified wine. From five hundred non-Saccharomyces isolates, twelve species were identified. The three most abundant species, Hanseniaspora uvarum, Lachancea thermotolerans, and Metschnikowia pulcherrima, representing 89% of the isolates, exhibited particularly high diversity with high growth performance variability when exposed to typical stress conditions associated with common enological parameters. Less abundant species included Issatchenkia orientalis, Torulaspora delbrueckii, Hanseniaspora vineae, Hanseniaspora osmophila, Candida zemplinina, Rhodotorula mucilaginosa, Hanseniaspora guilliermondii, Issatchenkia occidentalis, and Zygosaccharomyces bisporus. This is the first study providing insights into the identification and characterization of non-Saccharomyces species responsible for spontaneous Port wine production.
Highlights
IntroductionAlcoholic fermentation (AF) of grape juice into wine is a complex microbiological process involving various microorganisms, including mostly yeasts, and filamentous fungi and lactic acid bacteria
Alcoholic fermentation (AF) of grape juice into wine is a complex microbiological process involving various microorganisms, including mostly yeasts, and filamentous fungi and lactic acid bacteria.All these microorganisms leave their footprint depending on how long they are present and their dominance during the process [1]
568 Musts yeasts isolated from spontaneously fermented Port wine musts, 500
Summary
Alcoholic fermentation (AF) of grape juice into wine is a complex microbiological process involving various microorganisms, including mostly yeasts, and filamentous fungi and lactic acid bacteria. All these microorganisms leave their footprint depending on how long they are present and their dominance during the process [1]. Depending on their role in AF, yeasts are usually divided into two categories, the Saccharomyces and the non-Saccharomyces species. Non-Saccharomyces species may originate from the winery environment, including air, floor, and winery equipment [8,9,10]
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