 IVES 9 IVES Conference Series 9 Identification of riboflavin low producer yeasts to prevent the light-struck taste in white wines

Identification of riboflavin low producer yeasts to prevent the light-struck taste in white wines

Abstract

AIM: Wine quality maintenance during the storage is a fundamental aspect for both wine producers and consumers. Nowadays, great attention has been given to the light effect, causing detrimental changes of wine; indeed, light can induce off-flavours associated to the light-struck taste (LST)(1). This fault is due to photochemical oxidation processes in which riboflavin (RF) and methionine (Met) play an important role generating methanethiol (MeSH) and dimethyl disulphide (DMDS)(2), responsible of the unpleasant cabbage and onion-like odours that make wine undrinkable. Although it is well-known the contribution of yeasts in the final amount of these compounds in wine, microbiological strategies against the LTS defect limiting their release are not yet available. This study is part of the project “Innovative and sustainable approaches for the prevention of photo-induced defects in white wines and sparkling wines (Enofotoshield)” and in particular it aims at providing wineries with alternative microbiological approaches to counteract the LST.

METHODS: Four Saccharomyces cerevisiae strains of oenological interest (EC1118, IOC18, LS2 and AWRI796) have been compared to investigate the RF release during their growth in synthetic media (SMY and SMV) and Chardonnay must, simulating oenological conditions. Then, the RF release (including the derived flavones) was estimated by UPLC (Ultra-Performance Liquid Chromatography) analysis.

RESULTS: Results of this study revealed that RF production is influenced by the growth medium composition. Indeed, if the medium contains RF, the vitamin concentration increases over time while that of flavones remain constant; on the contrary, the opposite situation is verified in absence of RF. Moreover, investigations on other factors that could influence the RF release are still in progress (such as cell inoculum density, temperature, oxygen-limiting conditions, availability of nutrients). Taking in consideration that a lower concentration than 80-100 μg/L could limit the LST development, the best identified condition in terms of RF release was the growth on the Chardonnay must (12,8 μg/L) compared to the two synthetic media SMY and SMV (102,4 μg/L and 316,5 μg/L, respectively).

CONCLUSIONS

This study paves the way for the development of new approaches that limit the impact on the wine aromatic profile. Indeed, the choice of the growth cultural medium is a relevant factor in terms of RF and Met production. The next steps of the study will be the analysis of the Met release and of the intracellular content of both RF and Met.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Alessandra Di Canito

University of Milan,Ileana Vigentini – University of Milan Daniela Fracassetti – University of Milan Antonio Tirelli – University of Milan Roberto Foschino – University of Milan

Contact the author

Keywords

wine microbiology, light-struck taste, yeasts

Citation

Soil quality in Beaujolais vineyard. Importance of pedology and cultural practices

A pedological study was carried out from 2009 to 2017 in Beaujolais vineyard, to improve physical and chemical knowledge of soils. It was completed in 2016 and 2017 by the current study, dealing with microbial aspects, in order to build a reference frame for improved advice in soil management. Microbial biomass was measured on representative plots of the six most common soil types identified in Beaujolais and, for each soil type, on plots with different levels of the main impacting parameters: total organic carbon, pH, cation exchange capacity, extractable copper. A total of 59 soil samples were collected. Confirming the results of various trials carried out in Beaujolais over the past 20 years, the results of the present study showed that the soils were still alive, but exhibited a large variability of biological parameters, which appeared dependant on both pedological and anthropic factors. Therefore, a good interpretation of biological parameters and advice for vine growers must rely on a pedologically-based referential with differentiated main driving factors. For example, the control of pH is of primary importance in granitic soils and in no way organic matter addition can improve soil quality if pH is too low. Conversely, in calcareous soils, biological parameters are more directly affected by direct or indirect (cover crops for example) inputs of organic matter. The use of biological parameters, such as microbial biomass, is of great potential value to improve advice on agro-viticultural practices (soil management, fertilization, liming, etc.), basis of a sustainable wine production on fragile soils.

Application of a low-cost device VIS-NIRs-based for polyphenol monitoring during the vinification process

In red wine production, phenolic maturity is becoming increasingly important. Anthocyanins, flavonoids and total polyphenols content and availability significantly influence the harvest time of wine grapes while, during vinification process, their extraction strongly affects wine body, color and texture

Molecular approaches for understanding and modulating wine taste

Wine consumers generally demand wines having a perception of softer tannins and less ripe, having a heaviness and richness on palate (full-body wine) with a limpid and stable color. However, polyphenol
(tannins)-rich wines have been also correlated with unpleasant taste properties such as astringency and
bitterness when perceived at high intensities. Modulating these unpleasant properties could be important for consumer’s approval of wines.

The future of pesticide regulation in the EU – between precaution and proportionality

The article analyzes current developments in European pesticide regulation.

Nutrient absorption in vines (Vitis vinifera L., cv. Tempranillo blanco) under two water management approaches in a semiarid region of the north of Spain

Two treatments were studied in vines of cv. Tempranillo blanco (Vitis vinifera L.) during the 2012-2018 period in an experimental plot located in Rincón de Soto (La Rioja, Spain). Rainfed treatment (R0) was compared with respect to an irrigation treatment (R2) equivalent to 30% of the crop evapotranspiration (ET0) from fruitset to harvest phenological stages. Pre-veraison irrigation ranged from 43 (2014) to 66 mm/m2 (2018) while post-veraison irrigation ranged from 37 (2017) to 115 mm/m2 (2012).The normalized difference vegetation index (NDVI) was assessed by measures of reflectance, nutrients were determined by analysis of petioles sampled at veraison, grape production was determined at harvest as well as renewable wood weight was assessed at pruning time.