Effect of low temperature fermentation on the yeast-derived volatile aroma composition and sensory profile in Merlot wines

Highlights

• Merlot fermentation was done with different S. cerevisiae strains at low temperature.

• Wines with increased aroma were obtained by low temperature fermentation.

• Low temperature fermentation was correlated with high esters and low terpene wines.

• Higher alcohols and fatty acids concentration were yeast strain-dependent.

• Thermomaceration combined with low temperature fermentation improve red wine quality.

Abstract

Different winemaking practices have been tried to improve wine quality and differentiate wine styles. Low temperature fermentation has been proposed to enhance the aroma profile in young red wines. The aim of this work was to study how fermentation temperature affects the chemical composition, the concentration of yeast-derived volatile aroma compounds and the overall quality of young red wines. Thermomacerated Merlot grape must was fermented at 15 °C and 25 °C using five different Saccharomyces cerevisiae strains. Wines fermented at 15 °C displayed higher ethanol concentration, whereas differences in volatile acidity and colour were more related to the yeast strain used than the fermentation temperature. Sensory analysis could discriminate the wines fermented at two temperatures for each yeast tested. Low temperature fermentation produced wines with higher ester and lower terpene content compared to fermentation at 25 °C, whereas the fatty acids and higher alcohol concentraions were more associated to the yeast strain employed. In general, wines produced at low temperature were perceived as more aromatic, although this effect was strain-dependent. In summary, we were able to obtain red wines whit improved organoleptic characteristics, by combining thermomaceration and low temperature fermentation with cold adapted autochthonous yeast strains.

Introduction

Wine technology is continuously updating in order to produce wines with high quality to satisfy current consumer preferences. Wine quality is not easy to define, but ideally, involves intrinsic visual, taste, and aroma characters that are perceived above the expected average for that particular type of wine (Ilc, Werck-Reichhart, & Navrot, 2016). For consumers, the aroma profile generally determines acceptability and value of a wine (Van Wyk, Grossmann, Wendland, Von Wallbrunn, & Pretorius, 2019). Wine aroma is extremely complex and it is the cumulative effect of a diverse group of volatile compounds such as alcohols, aldehydes, esters, acids, terpenes and other minor components present in varying concentrations. According to their origin, wine aroma compounds are classified in three categories: primary or grape aroma; secondary or fermentation aroma; and tertiary or maturation aroma (Styger, Prior, & Bauer, 2011). The nature and amount of fermentative volatile compounds that make up the wine flavour are related with multiple factors such as the nitrogen content of the must, the fermentation temperature and the yeast strain (Dzialo, Park, Steensels, Lievens, & Verstrepen, 2017; Rollero et al., 2015; Styger et al., 2011).

Red wine is a macerated wine. The maceration facilitates the extraction of nutrients, phenolic compounds and other constituents from the pulp, skins and seeds to the grape juice. Traditionally, red wines include a long maceration step that occurs simultaneously with the alcoholic fermentation carried out at 20–28 °C (Casassa, Beaver, Mireles, & Harbertson, 2013). Some studies suggest that low temperature fermentation (10–15 °C) can result in wines with improved flavour (Kanellaki, Bekatorou, & Koutinas, 2014). Whereas fermentation at low temperature is a common practice for white and rosé wines, it has only recently been introduced to enhance the aromatic profile in young red winemaking. Nevertheless, fermentation at low temperature has some disadvantages like a slow diffusion of the phenolic compounds from the skin and pulp to the juice, and slower yeast growth and fermentation rate, which increases the risk of stuck and sluggish fermentations (Sacchi, Bisson, & Adams, 2005). One alternative way to overcome such limitations is the use of thermomaceration, where the maceration and the fermentation processes are dissociated (Baiano, Scrocco, Sepielli, & Del Nobile, 2016). Basic thermomaceration involves the heating of the skins to 60–70 °C for 10 min, followed by a short maceration at 45 °C for 6–10 h. The damages produced by heat on the grape's hypodermal cell membranes, result in a quick release of chemical compounds during subsequent maceration. Afterwards, the red must is pressed and the juice is cooled to begin the alcoholic fermentation (Casassa & Harbertson, 2014).

When fermentation is carried out at low temperature, changes in the yeast metabolism occur affecting the fermentation rate as well as the microbial ecology (Kanellaki et al., 2014). For example, some non-Saccharomyces species grow faster than Saccharomyces cerevisiae at low temperatures, increasing their ability to compete for nutrients in the medium (Maturano et al., 2015). Therefore, to prevent the growth of some undesirable non-Saccharomyces species, it is desirable to inoculate with cold-adapted S. cerevisiae strains, which allow for faster imposition and better control of the alcoholic fermentation (Kanellaki et al., 2014; Van Wyk et al., 2019). In a previous work, several S. cerevisiae strains were regionally selected for red must fermentation at low temperature and wines with improved colour and aroma intensity were obtained (Massera et al., 2012).

The aim of this work was to evaluate the effect of low temperature on the fermentation performance, the physicochemical composition and the synthesis of yeast-derived volatile aroma compounds in a Merlot juice fermented with autochthonous cold-adapted and commercial S. cerevisiae strains.