Often blamed for bringing green aromas and astringency to wines, the use of stems is also empirically known to improve the aromatic complexity and freshness of some wines. Although applied in different wine-growing regions, stems use remains mainly experimental at a cellar level. Few studies have specifically focused on the compounds extracted from stems during fermentation and maceration and their potential impact on the must and wine matrices. We identified current knowledge on stem chemical composition and inventoried the compounds likely to be released during maceration to consider their theoretical impact. In addition, we investigated existing studies that examined the impact of either single stems or whole clusters on the wine quality. Many parameters influence stems’ effect on the wine, especially grape variety, stem state, how stems are incorporated, when they are added, and contact duration. Other rarely considered factors may also have an impact, including vintage and ripening conditions, which could affect the lignification of the stem.

To date, there are no specific guidelines for the use of bioacidifying yeasts in winemaking. In this work, we aimed to characterize an oenological strain of Lachancea thermotolerans (Lt), a non-Saccharomyces lactic acid-producing yeast, and to test different sequential inoculation conditions with Saccharomyces cerevisiae (Sc). The results of bench scale vinifications showed that both the strategy of inoculating Sc 12 h after Lt and the mixing of Lt and Sc during fermentation delivered an acceptable increase in lactic acid (2 g/L) and a decrease in pH (about 0.15 units). Therefore, both strategies were implemented in winery experiments. Our results at the cellar scale showed no increase in acidity, which was likely due to the presence of indigenous yeasts. Overall, our experience shows the difficulty of translating laboratory protocols into cellar experiments and calls for further research into new strategies for implementing acidifying yeasts.

Interest in Metschnikowia (M.) pulcherrima is growing in the world of winemaking. M. pulcherrima is used both to protect musts from microbial spoilage and to modulate the aromatic profile of wines. Here, we describe the isolation, characterization, and use of an autochthonous strain of M. pulcherrima in the vinification of Chasselas musts from the 2022 vintage. M. pulcherrima was used in co-fermentation with Saccharomyces cerevisiae at both laboratory and experimental cellar scales. Our results showed that M. pulcherrima does not ferment sugars but has high metabolic activity, as detected by flow cytometry. Furthermore, sensory analysis showed that M. pulcherrima contributed slightly to the aromatic profile when compared to the control vinifications. The overall results suggest that our bioprospecting strategy can guide the selection of microorganisms that can be effectively used in the winemaking process.

The removal of stems prior to maceration during red winemaking is generally associated with an improvement in wine quality. However, in recent years, increased interest in the use of stems in winemaking has been observed among winegrowers. Different advantages of this practice have been listed in the literature. In order to better understand their role during winemaking, stems of ten red grape varieties from different winegrowing regions of Switzerland were studied to determine which minerals, acids and polyphenols are extracted under simulated alcoholic fermentation. The composition of the extracts revealed differences between the grape varieties. In addition, the growing conditions and the terroir seem to have an influence on the compounds extracted from the stems, especially the mineral composition such as potassium and copper. Among the extracted polyphenols, phenolic acids and proanthocyanidins were mostly found in the stem extracts, especially caftaric acid, catechin and procyanidin B1. Their concentrations were significant compared to the average values found in wines.

A growing interest in sustainable viticulture has led to the development of fungus-resistant grape (FRG) varieties, but their acceptance by consumers remains uncertain. This study explores Swiss consumers’ perceptions of wines made from FRG varieties compared to traditional grape varieties. Specifically, it investigates (i) potential differences in consumer acceptance of FRG wines and traditional wines, (ii) segmentation of consumers based on their appreciation of FRG wines, and (iii) the influence of information about FRG on consumer perception. To address these questions, we conducted a multi-phase study combining chemical wine analysis, expert sensory profiling and consumer blind tastings of FRG wines and traditional and commercial wines in three cities across Switzerland (Nyon (Vaud), Liebefeld (Bern) and Wädenswil (Zurich)). Half of the participants were informed that they were tasting wines made from FRG varieties, while the other half were not. The results indicate that FRG wines are, on average, as appreciated as traditional varieties. Furthermore, consumers can be segmented into three distinct preference groups. This study identifies three key drivers of consumer acceptance: organoleptic attributes, wine-knowledge of the targeted consumer cluster and prior awareness of FRG. While additional information on the environmental benefits of FRG wines did not influence overall consumer appreciation, one cluster of consumers was affected by the information provided. These findings have important implications for winegrowers, suggesting that marketing strategies should be tailored to different consumer segments, emphasising sensory qualities while strategically using information disclosure.

The monitoring of must fermentation in a bioreactor, in which the main physico-chemical parameters are tightly controlled, can provide useful analytical information transferable to winemaking on a larger scale. In this experiment, we followed the growth of Saccharomyces cerevisiae during the bioreactor-assisted alcoholic fermentation of a Chasselas must by means of flow cytometry. We used fluorescent dyes and volumetric counting to monitor cell viability and concentration for two weeks. Our study suggests that the use of flow cytometry during bioreactor-assisted alcoholic fermentation provides various types of information—viz., cell viability, number and function—in a timely manner, and that the process can therefore be used effectively to inform experimentation at this scale.