Effects of winemaking variables on the chemical and sensory quality of Schiava wines up to one year storage in bottle

Abstract

The interactive effects of three major enological variables were evaluated on the quality of Schiava wine up to one year of storage in bottle. Differing from most red varieties, ‘Schiava’ grapes contain peonidin-3-glucoside as the main anthocyanin; together with other factors (e.g. low tannin content, high pH), the loss of peonidin-3-glucoside is thought to be a main cause for discolouration in the derived wines [1,2]. A primary objective was to test specific variables (e.g. grape freezing), for their possible ability to increase the extraction of pigments from the grapes, or to increase the colour stability in wine. Secondarily, potential interactive effects of variables such as grape freezing and the malolactic fermentation were targeted, as it previously showed to cause differences in the phenolic and volatile profiles of white wines made with other grape varieties [1]. The evaluated variables were: (1) grapes frozen or not for 2 weeks at -20 ^oC; (2) fermentation with or without fermentative maceration; (3) inoculum with Saccharomyces cerevisiae, or co-inoculum with S. cerevisiae and Oenococcus oeni. The storage in bottle was conducted in darkness at 4 ^oC for one year. Basic oenological parameters, colour, spectroscopical parameters [3,4], volatile profile, and polyphenols were monitored overtime. The sensory analysis was conducted after storage. The fermentative maceration was here excluded as a factor to use for comparison. The major trends associated with the grape freezing and the co-inoculum manifested in differences in the volatiles, condensed tannins, and colour profiles. Wines made without fermentative maceration presented a neat effect from the grape freezing; this was not so clear for wines made with fermentative maceration. In wines made without fermentative maceration, the grape freezing factor was associated to distinctive visual sensory attributes such as ‘light pink’ and ‘pink salmon’, and aroma descriptors such as ‘nutty/almond’ and ‘tropical/banana’. Despite the higher initial content of peonidin-3-glucoside extracted from frozen grapes, no significant difference was found after bottle storage in relation to grape freezing. Interestingly, the colorimetric and visual parameters were instead positively impacted by grape freezing; this was attributed to the extraction from the frozen grapes of more chemical components participating in the colour stabilization. Overall, these factors greatly influenced the wine quality, offering the winemakers strategies to modulate the colour of Schiava wine even after one year of storage.

References

[1] Darnal, A., Poggesi, S., Ceci, A. T., Mimmo, T., Boselli, E., & Longo, E. (2023). Interactive effect of pre-fermentative grape freezing and malolactic fermentation on the anthocyanins profile in red wines prone to colour instability. Eur. Food Res. Technol., 249(8), 2045-2065

[2] Darnal, A., Poggesi, S., Merkytė, V., Longo, E., & Boselli, E. (2024). South-Tyrolean pinot blanc identity: Exploration of chemical and sensory profile changes ascribed to vineyard locations and winemaking variables. Food chem: X, 24, 101824

[3] Boulton, R. B. (1996, June). A method for the assessment of copigmentation in red wines. 47^th annual meeting of the American Society for Enology and Viticulture, Reno, NV (Vol. 97)

[4] Heras-Roger, J., Alonso-Alonso, O., Gallo-Montesdeoca, A., Díaz-Romero, C., & Darias-Martín, J. (2016). Influence of copigmentation and phenolic composition on wine color. J. Food Sci. Tech., 53, 2540-2547