 IVES 9 IVES Conference Series 9 Tuning the pH during the fermentation has a strong effect on the wine protein composition and the stability of the resulting white wines

Tuning the pH during the fermentation has a strong effect on the wine protein composition and the stability of the resulting white wines

Abstract

AIM: Previous results have shown the impact of the pH on the stability of white wine proteins. In a context of global warming that implies increases in ethanol content and pH, we wanted to compare for the same initial must (given composition in polysaccharides, polyphenols, ions, _) the impact of the pH on the protein composition after fermentation. Several white wine varieties were considered.

METHODS: Vinifications were carried out using musts from Sauvignon, Muscat, Sylvaner, Riesling, Gewurztrminer, and Pinot Gris). The pH of the initial musts was adjusted to 3.0, 3.3, 3.6 and 3.9. For each wine thus obtained, heat tests (heating at 40°C for 4 hours) were carried out and proteins were analyzed and quantified by gel electrophoresis.

RESULTS: On the whole, protein concentrations in wines decreased during fermentation. However, this decrease was more marked for the lowest pH (3.0 and 3.3), as well as for some proteins (chitinases, b-glucanases). Thus the total concentration of proteins was higher at pH 3.9. The turbidity measured after heat tests evolved differently: a maximum was observed at pH 3.6 in the present experimental conditions (40°C- 4h).

CONCLUSIONS

This study confirms that the pH has a decisive impact on the protein composition in white wines, with higher pH favoring their conformational stability during winemaking. However, haze formation due to heat-induced denaturation of proteins is higher at high pH. This trend was observed whatever the studied variety, but with more or less haze intensities. This indicated also an impact of non-protein compounds, whose composition strongly depends on the grape variety.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Céline Poncet-Legrand

INRAE,Eric MEISTERMANN, IFV Aude VERNHET, Institut Agro, Montpellier SupAgro Philippe COTTEREAU, IFV Frédéric CHARRIER, IFV Patrick CHEMARDIN, INRAE Céline PONCET-LEGRAND, INRAE

Contact the author

Keywords

white wines, haze formation, proteins, pH

Citation

Identification of 4-hydroxy-2-nonenal, a gamma nonalactone precursor in must and wine from Bordeaux cultivars

Various molecular compounds are responsible for the complex mixture of fragrances that give wine its aroma. In particular, the ‘cooked fruit’ aroma found in red wines from hot and/or dry vintages or from the vinification of late harvested grapes has been intensively investigated in recent years. Lactones and especially γ-nonalactone were found to be responsible for the ‘cooked fruit’

Influence of climatic conditions on grape composition of Tempranillo in La Mancha DO (Spain)

The aim of this work was to analyze the variability in grape composition of the Tempranillo cultivar related to climatic conditions, in La Mancha Designation of Origin. Grape composition (sugar content, total acidity, pH, malic acid, and total and extractable anthocyanins) recorded during ripening, were analysed for the period 2000-2019. The weather conditions at daily time scale, recorded during the same period, were also evaluated. The relationships between grape parameters with climatic variables related to temperature and to water deficits, referring different periods between phenological events along the growing cycle, were evaluated using regression analysis. High variability in grape composition was observed in the period analysed. Total acidity varied between 3.7 and 7.3 gL-1 while malic acid varied between 1.2 and 4 gL-1. The extractable anthocyanins ranged between 526 and 972 mgL-1, and total anthocyanins ranged between 922 and 1388 mgL-1, being the lowest values recorded in the hottest year (2017). Total acidity decreased 0.77 gL-1 for an increase of 100 GDD, while malic acid decrease in 0.42 gL-1 for the same GDD increase, being the period between veraison and harvest the one that seemed to have higher influence on acidity. In addition, it was confirmed that increasing water deficits decreased acidity. Total and extractable anthocyanins increased in about 210 and 105 mgL-1, respectively, with an increase of 100 GDD from veraison to harvest, and the increase in water deficits favour the increase of anthocyanins, both total and extractable anthocyanins. Total and extractable anthocyanins concentration increased in 35 and 22 mgL-1 per an increase of 10 mm in the water deficit. These results can be of interest to understand the potential changes that grapes composition may suffer under future warmer climates.

Aroma and quality assessment for vertical vintages using machine learning modelling based on weather and management information

Wine quality traits are usually given by parameters such as aroma profile, total acidity, alcohol content, colour and phenolic content, among others

Lactiplantibacillus plantarum – A versatile tool for biological deacidification

Malolactic fermentation (MLF) is a secondary wine fermentation conducted by lactic acid bacteria (LAB). This fermentation is important in winemaking as it deacidifies the wine, converting L-malic acid into L-lactic acid and carbon dioxide, and it contributes to microbial stability. Wine pH is highly selective, and at pH below 3.5 generally only strains of O. oeni can survive and express malolactic activity, while under more favorable growth conditions above pH 3.5, species of Lactobacillus and Pediococcus may conduct the MLF. Among the LAB species Lactiplantibacillus plantarum strains have shown most interesting results under hot climate conditions, not only for their capacity to induce MLF, but also for their homo-fermentative properties towards hexose sugars, which makes them suitable for induction of MLF in high pH and high alcohol wines, when inoculated at the beginning of alcoholic fermentation.

Influence of grapes origin and yeast strain on aroma profile of corvina and corvinone dry passito wines

Valpolicella is a wine region characterized by a wide use of the technology of grape drying for the production of two red passito wines, recognized as PDOs, “Recioto della Valpolicella” and the most famous “Amarone della Valpolicella”. Geographical origin of the grapes can influence wine composition by grape chemical composition yeast behaviour during fermentation. This study investigates the impact of different commercial yeast strains on aroma profiles of wines produced with withered grapes of different origins. In addition, the influence of spontaneous fermentation is also considered. METHODS: Experimental red wines were produced with a standard winemaking protocol with withered Corvina and Corvinone grapes obtained from two different geographical areas within the Valpolicella region. Fermentations were carried out with four different commercial yeasts plus a spontaneous fermentation. Wines were analysed by means of SPE- and SPME-GC-MS techniques and sensory analysis (sorting task).