ROUND TABLE #4 Yeast, bacterial and plant resources for sustainable winemaking processes

During the ROUND TABLE #4 – Yeast, bacterial and plant resources for sustainable winemaking processes, held at Macrowine 2021 there were six interesting presentations from across the world.

ROUND TABLE #4.1 – Rocio ESCRIBANO VIANA – ICVV, Instituto de Ciencias de la Vid y el Vino, University of La Rioja (Spain) – Bioprotective effect of non-Saccharomyces yeasts in wines made without SO₂

The objective of this work was to evaluate the bioprotective effect of a mixed inoculum of non-Saccharomyces  yeasts (Torulaspora delbrueckii and Lachancea thermotolerans 70/30) in two consecutive vintages (2018 and 2019). Three strategies were carried out in triplicate: spontaneous fermentation in sulphited must, spontaneous fermentation in non sulphited must and inoculated fermentation (non-Saccharomyces mixed inoculum) in non sulphited must. In all cases, after 72 hours of fermentation the vats were seeded with a commercial  Saccharomyces cerevisiae yeast. The presence in the medium of lactic and acetic bacteria and the chemical composition of the wines were evaluated. What did the obtained results indicate? Was the bioprotective effect of non-Saccharomyces yeasts inoculation determined by the success of the implantation?

ROUND TABLE #4.2 – Vasileios ENGLEZOS – University of Turin, DISAFA (Italy) – Effect of environmentally friendly vineyard protection strategies on yeast ecology during fermentation

This study evaluated the effect of a wide range of environmentally friendly products applied in the vineyard on grape yeast ecology at harvest, as well as during spontaneous and inoculated fermentations in winery and laboratory scale conditions. Yeast ecology was investigated using culture-dependent (plate counts) and -independent (Next Generation Sequencing) methods. Main oenological parameters and volatile compounds were monitored during spontaneous and inoculated fermentations. Spearman’s correlation was used to assess associations between ASVs changes and chemical composition observed over fermentation. Which significant differences were observed among the alternative and conventional treatments, compared to the controls, in terms of yeast population and biodiversity? Could yeast ecology in fermenting musts be correlated to specific antifungal products and inoculation protocol employed?

ROUND TABLE #4.3 – Ana Belén BAUTISTA-ORTÍN – University of Murcia (Spain) – Effect of plant fining agents in the must flotation process. Functional characterization

Flotation is one of the most used processes for clarifying white grape must after the pressing process. To date, gelatine is the more used fining agent, its action being improved when combined with bentonite and silica sol. However, in recent years, there is a growing commercial interest in replacing this animal origin protein with plant proteins, due, on the one hand, to the problems associated with allergies and, on the other hand, also thinking in the vegan wine consumers. However the efficiency of plant proteins as floculating agents are lower than gelatine and varies among them, the reason behind the different behaviour being unknown. The objective of this work was to compare the flocculating efficiency of a commercial gelatine, a pure pea protein and the same pea protein chemically modified and to relate this efficiency  to their amino acid composition and protein functions.

ROUND TABLE #4.4 – Fernando SALAZAR – Laboratorio de Fermentaciones Industriales, Facultad de Ciencias Agronómica y de los Alimentos, Pontificia Universidad Católica de Valparaíso (Chile) – Application of UV-LED in wine as an alternative to sulphur dioxide

Sulfites (SO₂) are commonly used in the wine industry to preserve products during storage for antiseptic and antioxidant purposes. However, the presence of sulfites at varying concentrations has been linked to allergic reactions in some consumers, such as dermatitis, urticaria, abdominal pain, among others. UV-LED irradiation has been is an attractive technology of non-thermal nature and is an alternative to partially or totally replace the addition of SO₂ to wine, due to its antimicrobial effect. In this study, the effect of the UV-LED irradiation on the activity of Acetobacter aceti ATCC 15973 of white wine (Sauvignon blanc) and red wine (Pinot noir) was evaluated. A laboratory scale static UV LED irradiation system was designed, composed of four diodes with wavelengths of 278 nm (8-12 mW), 275 nm (3-5 mW) and 265 nm (1-3 mW) and irradiation times of 10, 20 and 30 min. What di the results indicate? Could this technology  be an advantageous alternative to avoid the excessive use of sulphites in wine products?

ROUND TABLE #4.5 – Chantal MAURY – Impact of electrolyzed water applied as an alternative treatment in vineyard on grape and wine quality

Chantal MAURY, USC 1422 GRAPPE, INRAE, Ecole Supérieure d’Agricultures, SFR 4207 QUASAV, 55 Rue Rabelais,
BP 30748, 49007 Angers CEDEX 01, FRANCE
Mario GABRIELLI, USC 1422 GRAPPE, INRAE, Ecole Supérieure d’Agricultures, SFR 4207 QUASAV, 55 Rue Rabelais,
BP 30748, 49007 Angers CEDEX 01, FRANCE
Philippe CHRETIEN, Institut Français de la Vigne et du Vin – Pôle Centre Val de Loire, 42, rue Georges Morel – BP 60057, 49070 Beaucouzé, FRANCE
Dominique LE MEURLAY, USC 1422 GRAPPE, INRAE, Ecole Supérieure d’Agricultures, SFR 4207 QUASAV, 55 Rue Rabelais, BP 30748, 49007 Angers CEDEX 01, FRANCE
Christophe GRELIER, Institut Français de la Vigne et du Vin – Pôle Centre Val de Loire, 42, rue Georges Morel – BP 60057, 49070 Beaucouzé, FRANCE
Vanessa LANÇON-VERDIER, USC 1422 GRAPPE, INRAE, Ecole Supérieure d’Agricultures, SFR 4207 QUASAV, 55 Rue Rabelais, BP 30748, 49007 Angers CEDEX 01, FRANCE
Luca ROLLE, Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Paolo Braccini 2, 10095 Grugliasco, TO, ITALY
Email contact: c.maury[@]groupe-esa.com

The main issues in viticulture are to highly decrease the use of phytochemicals. Electrolyzed water (EW) is one of the possible alternative when illness pressure is not too high. The objective of that work was to characterize the impacts on grape and wine quality when using EW compared to those obtained from organic and conventional production.

Trials were performed in real vintner parcels of Cabernet franc and Chenin Blanc in the Loire Valley. The control treatment (VITI) was the usual practices of the vintners and the EW treatment was 50% of VITI treatment and 50% of EW for logistic reasons. Grapes were harvested at the date selected by the vintners.

Microvinifications (about 40L each) were realized with a standardized. Grapes and wines were analyzed with usual analyses in addition with hyperspectral imaging for grapes and TCA analyses for wines.

The results showed that the total polyphenol content and in particular the total anthocyanin content was higher when the grapes were treated by the electrolyzed water. The most important change in the composition was linked to the concentration of peonidine-3-O-glucoside. The oenological ripeness was slightly or not modified depending on the vintage. If the differences between the modalities were not easy to comprehend with classical methods, hyperspectral imaging and Raman spectroscopy allowed a very good classification of berries depending on the vineyard treatments. However, after vinification, differences observed in grapes about sugar content were also found in wine just after the alcoholic fermentation. But differences were reduced in wines after malolactic fermentation or after bottling suggesting that wine quality was not really impacted by the EW treatment. Moreover, analyses showed that the use of electrolyzed water in the vineyard did not add a risk of developing trichloroanisoles in wine during fermentation.

Thus, the use of electrolyzed water is possible in light of impact of grape and wine quality. Its use has now to be validated by its efficency at a moderate level of illness pressure in vineyards.

ROUND TABLE #4.6 – Guilherme Martin – Bacterial community structure in different wine appellations – biotic and abiotic interaction in grape berry and its impact on Botrytis cinerea development

Guilherme Martins^1,2, Candela Baquero³, Pauline Mazeau¹, Audrey Barsacq¹, Laurence Geny¹, Isabelle Masneuf-Pomarède^1,2 , Miren Andone Recalde³, Iratxe Zarraonaindia^3,4.
¹ Université de Bordeaux, ISVV, Unité de Recherche Oenologie ea 4577, USC 1366 INRAE, Bordeaux inp, 33140 Villenave D’Ornon, France
² Bordeaux Sciences Agro, 33170 Gradignan Cedex, France
³ Department of Genetics, Physical, Anthropology & Animal Physiology, Faculty of Science and Technology, University of the Basque Country (upv/ehu), Leioa, Spain
⁴ Ikerbasque, Basque Foundation for Science, Bilbao, Spain.
Email contact: guilherme.martins[@]agro-bordeaux.fr

AIM: An in-depth knowledge on the conditions that trigger Botrytis disease and the microbial community associated with the susceptibility/resistance to it could led to the anticipation and response to the Botrytis emergence and severity. Therefore, the present study pretends to establish links between biotic and abiotic factors and the presence/abundance of B. cinerea.

METHODS: Several grape varieties from 4 different wine appellations in France and Spain have been studied at different maturity stages to analyse: 1) B. cinerea abundance (established by qPCR), 2) grape composition parameters (comprising water activity measuring, exudates composition, phenologic stage, gluconic acid, calcium, etc), and 3) grape berries microbial community diversity and composition (using 16S rRNA and ITS amplicon sequencing).

RESULTS: Preliminary analysis of the results obtained through 16S rRNA Next Generation Sequencing revealed differences in microbial richness and bacterial composition between the vineyards. Both alpha and beta diversities correlated with fruit maturity, where grapes at harvest stage showed significantly higher richness and a dissimilar bacterial composition. In addition, bacterial community structure differed between wine appellations.

CONCLUSIONS: The study will increase significantly our understanding of the ecology of microbial associated to different grape varieties and viticulture areas. Additionally, it will generate knowledge about the factors and microbiota contributing to the incidence of the Botrytis disease, helping identify areas under higher/lower risk of infection within a vineyard. The later is of high interest in order to conduct targeted preventive strategies and the reduction or more controlled number of chemical treatments, minimizing costs and ensuring obtaining wines of higher quality.

Videos of the round table held during Macrowine virtual (June 23-30, 2021)