Abstract
Narince is a native white grape variety of Vitis vinifera L grown in Tokat and produces rich and balanced wines often with a greenish yellow tint and delicate fruity flavour. Fermentation by indigenous yeasts may produce wines with complex oenological properties that are unique to specific region. In this study yeast population during alcoholic fermentation of Narince was investigated. Yeasts were identified by PCR-RFLP analysis of the 5.8 ITS rRNA region and sequence information for the D1/D2 domains of the 26S gene. Eight different species belonging to nine genera were identified as: Hanseniaspora uvarum , Hansenispora guilliermondii , Pichia kluyveri , Metschnikowia spp., Pichia occidentalis , Torulaspora delbrueckii , Candida zemplinina , Lachancea thermotolerance and Saccharomyces cerevisiae . Hanseniaspora guilliermondii, Metschnikowia spp., Pichia occidentalis and Pichia kluyveri were identified only in the early stage of fermentation. Selected yeasts tested for their physiological traits, ethanol, SO2 , temperature, pH tolerance, H2 S production, killer and enzymatic activity, fermentation rate, flocculation characteristic, foam, volatile acid and volatile compounds production. Among the yeasts, one,Lachancea thermotolerance and four Saccharomyces cerevisiae strain showed remarkable technological properties and results were compared with those obtained by using commercial starter culture.
Highlights
At the beginning of the spontaneous fermentation a total yeast count on YPD medium was 5 log cfu/mL and they increased to 6.7 log cfu/mL at the middle of fermentation
S. cerevisiae and Hanseniaspora uvarum were the dominant species at the beginning and Metschnikowia spp, Pichia kluyveri, Hansenispora guilliermondii, Pichia occidentalis and Candida zemplinina were isolated with less extend at the beginning of fermentation
At the middle of fermentation, S. cerevisiae, Hanseniaspora uvarum, Candida zemplinina started to overcome yeasts and others were not isolated from middle of fermentation with the exception of Lachancea thermotolerance and Torulaspora delbrueckii which were not observed at the beginning
Summary
Narince grape is one of the most important native white varieties grown in North-east Anatolia Region of Turkey. Narince produces rich and balanced wines that often have a greenish yellow tint and delicate, fruity aromas. Because of their balanced acidity, these wines are suitable for ageing and acquire a rich and complex bouquet over time [1, 2]. One of the important factors affecting wine quality is yeast. Grape must harbour indigenous NonSaccharomyces spp. and Saccharoyces yeasts. Many studies state that production of wines by indigenous yeasts isolated from its terroir can contribute to the regional character of wines, especially wine flavour [3,4,5]. Winemakers usually prefer to use Saccharomyces (S.) cerevisiae strains unique to the region because those strains adapt to regional conditions and can readily dominate must during alcoholic fermentation [6]
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