Abstract
The aim of the present study was to identify yeasts in grape, new wine “federweisser” and unfiltered wine samples. A total amount of 30 grapes, 30 new wine samples and 30 wine samples (15 white and 15 red) were collected from August until September, 2018, from a local Slovak winemaker, including Green Veltliner (3), Mūller Thurgau (3), Palava (3), Rhein Riesling (3), Sauvignon Blanc (3), Alibernet (3), André (3), Blue Frankish (3), Cabernet Sauvignon (3), and Dornfelder (3) grapes; federweisser and unfiltered wine samples were also used in our study. Wort agar (WA), yeast extract peptone dextrose agar (YPDA), malt extract agar (MEA) and Sabouraud dextrose agar (SDA) were used for microbiological testing of yeasts. MALDI-TOF Mass Spectrometry (Microflex LT/SH) (Bruker Daltonics, Germany) was used for the identification of yeasts. A total of 1668 isolates were identified with mass spectrometry. The most isolated species from the grapes was Hanseniaspora uvarum, and from federweisser and the wine—Saccharomyces cerevisiae.
Highlights
Yeasts naturally occur in wines and vineyards and are especially common on the grapes
Some species of parasitic fungi or environmental bacteria might be only found in grapes, while other microorganisms like yeast, lactic acid and acetic acid bacteria occur during the winemaking process [10]
A higher number of yeasts were detected in “federweisser” than in grape
Summary
Yeasts naturally occur in wines and vineyards and are especially common on the grapes. Population of yeast species on the grape is not constant and increases during the ripening process. Kloeckera apiculata is a lemon-like cell shape yeast, which colonizes the grape surface [1]. Kloeckera apiculata comprises more than 50% of the total healthy grape microbiota. Other yeasts like Kloeckera were isolated from the surface of the grapes, which included mainly genera Metschnikowia, Candida, Cryptococcus, Pichia, Rhodotorula, Zygosaccharomyces or Kluyveromyces [2]. All the yeasts associated with natural microbiota of grapes are wild yeast strains or non-saccharomyces. Despite the presence of those yeasts on the surface of grapes, the wine production consists of subsequent fermentation stages, Fermentation 2020, 6, 5; doi:10.3390/fermentation6010005 www.mdpi.com/journal/fermentation
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