Addition of glutathione-rich inactivated yeasts to white musts: effects on wine composition and sensory quality

The wine spoilage caused by Brettanomyces bruxellensis is one of the global concerns for winemakers. Detecting the presence of B. bruxellensis using routine laboratory culture techniques becomes challenging when cells enter the viable but not culturable (VBNC) state. This study aims to investigate the impact of p-coumaric acid (a volatile phenol precursor) and micronutrients on B. bruxellensis’ culturability, viability, and volatile phenol production under sulfite stress. In red wine, exposure to a high sulfite dose (100.00 mg L-1 potassium metabisulfite) resulted in immediate cell death, followed by a recovery of culturability after two weeks.

Grapevine (Vitis spp.) is greatly influenced by climatic conditions and its economic value is therefore directly linked to environmental factors. Among these factors, temperature plays a critical role in vine phenology and fruit composition. In such conditions, elucidating the mechanisms employed by the vine to cope with heat waves becomes urgent. For the past few years, our research team has been producing molecular and metabolic data to highlight the molecular players involved in the response of the vine and the fruit to high temperatures [1]. Some of these temperature-sensitive genes are currently undergoing characterization using transgenesis approaches coupled or not with genome editing, taking advantage of the Microvine genotype [2].

The fungicidal effect of UV-C radiation (100-280 nm wavelength) is well known, but its applicability for the control of pathogenic molds of grapes is conditioned by its effect on the host and by the risks inherent in its handling[1].
As an alternative, the effect in vitro of UV-B radiation (280-315 nm) on the main pathogenic molds of grapes has been studied: Botrytis cinerea, Aspergillus niger, Penicillium expansum and Rhizopus stolonifer.

Recently, foliar treatments with mineral-based compounds have shown positive effects on grapevine production by protecting grape from thermal excesses and reducing the decoupling between technological and phenolic maturity caused by climate change. Unraveling the effect of mineral particle applications on grape-associated microbes is pivotal for successful wine processing, due to the influence of the microbiota on wine composition and stability. To our knowledge, this is the first work that comprehensively studied the effects of kaolin and chabasite-rich zeolitites treatments on grape-related microorganisms (by real-time PCR quantification of total fungi, Hanseniospora uvarum, Metschnikowia pulcherrima, plant-associated bacteria and lactic acid bacteria), the expression of genes related to the flavonoid biosynthesis (PAL1, CHS1, F3H2, DFR, LDOX, UFGT, MYBA1, GST4, FLS4 genes) and the berry composition (°Brix, pH, acidity and anthocyanin concentrations) in cv. Sangiovese during ripening in two growing seasons (2019 and 2020).

The yeast ecosystem in grape musts is quite broad and depends on the region and the health of the grapes. Within this, there are yeasts that can generate fermentative deviations and/or cause defects in the wine. It is very important to address this issue because there are significant economic losses in the wine industry when the fermentation process and/or the organoleptic characteristics of the wine are negatively affected, even more today since climate change has a marked effect on the composition of this ecosystem. The aim of this work is to characterize the behavior regarding detrimental oenological features of potential spoilage yeasts isolated from viticultural environments.