Abstract
In the current scenario of climatic warming, the over-ripening of grapes increases the sugar content, producing flat and alcoholic wines with low acidity, high pH and low freshness. Additionally, a high pH makes wines more chemically and microbiologically unstable, requiring a higher sulphite content for preservation. Some strains of Lachancea thermotolerans can naturally lower the pH of wine by producing lactic acid from sugars; this pH reduction can reach 0.5 units. The industrial performance of four selected strains has been compared with that of two commercial strains and with that of Saccharomyces cerevisiae. The yeasts were assessed under variable oenological conditions, measuring lactic acid production and fermentative performance at two fermentation temperatures (17 and 27 °C), and in the presence or absence of sulphites (25 and 75 mg/L). Lactic acid production depends on yeast populations, with higher concentrations being reached when the microbial population is close to or above 7-log CFU/mL. A temperature effect on acidification can also be observed, being more intense at higher fermentation temperatures for most strains. Ethanol yield ranged from 7–11% vol., depending on the fermentation conditions (temperature and SO2) at day 12 of fermentation, compared with 12% for the S. cerevisiae control in micro-fermentations. The production of fermentative esters was higher at 27 °C compared with 17 °C, which favoured the production of higher alcohols. Volatile acidity was moderate under all fermentation conditions with values below 0.4 g/L.
Highlights
In warm areas, Vitis vinifera L. usually produces mature grapes with an excessive sugar content, and a high potential alcohol together with low acidity and high pH values
The aim of this work was to compare the oenological potential of strain L3.1 with other selected L. thermotolerans strains from warm areas and with a Saccharomyces cerevisiae control strain 7VA
The S. cerevisiae 7VA (Sc) yeast strain fermenting at high temperature (27 ◦C) and at both total SO2 doses showed the fastest fermentative kinetics
Summary
Vitis vinifera L. usually produces mature grapes with an excessive sugar content, and a high potential alcohol together with low acidity and high pH values. This situation is made even worst because of global warming. The pH is a key parameter affecting wine stability and microbiological developments. The acidity has a strong influence on the sensory quality and freshness of the wine. To obtain a fresh wine, it is necessary to take into account parameters such as aroma, alcohol content, acidity, colour and more [1,2]. Aromatic freshness is related to the production of acetate esters, produced during fermentation from higher alcohols by the Ehrlich transamination pathway [3], and to some ethyl esters
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