Effects of major enological variables on the evolution of the chemical profile in Schiava over the vinification: an experimental design approach

Abstract

Schiava cv. (germ. Vernatsch) is a group of grape varieties used for winemaking (e.g. Kleinvernatsch-Schiava gentile, Grauvernatsch-Schiava grigia, Edelvernatsch-Schiava grossa) historically reported in Northern Italy, Austria, Germany and Croatia. Beside common phenotypic traits, these varieties have been also hypothesized to share a common geographical origin in Slavonia (Eastern Croatia). Nowadays, Schiava cv. are considered historical grape varieties of northern regions of Italy such as Lombardy, Trentino and South Tyrol. Traditionally widely consumed locally and also exported, over the past decades there has been a steady drop in production of these grapes, although with a parallel increase in wine quality. In this report, the effects of three main enological variables on the chemical components of Schiava produced in South Tyrol (var. Schiava grossa) are investigated from grape to bottle. Employing a complete 2-levels/3-factors systematic experimental design (8 theses in triplicates), this study primarily aimed at evaluating the effects of 1) pre-fermentative grape freezing, 2) fermentative maceration, and 3) co-inoculum of yeasts with malolactic bacteria, on the Schiava chemical profile and its overtime evolution, considering also potential interacting factors. The measured parameters included basic enological determinations (e.g. residual sugars, organic acids and alcohol content, measured by specific enzymatic methods or by official methods), quantitative or semi-quantitative phenolic determinations (anthocyanins and derivatives, non-anthocyanins phenolics and condensed tannins – major and minor components – analyzed by LC-QqQ/MS [1]) and the volatile aroma profile (determined by HS-SPME-GCxGC-ToF/MS [2]). In particular, the effects of the applied treatments on the content of specific chemical markers (e.g. highly polar minor condensed tannins [3]) have been highlighted. Besides, a dependance of the ratio between the two main Schiava’s anthocyanins (peonidin-3O-glu and malvidin-3O-glu) on the applied pre-fermentative (e.g. grape freezing) and fermentative (e.g. co-inoculum with malolactic bacteria) conditions was observed [4,5]. Finally, the profile of the major and minor cyclic (high-polarity) condensed tannins was investigated over fining and stabilization steps.

References

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[3] Longo, E., Rossetti, F., Jouin, A., et al. (2019). Food chemistry, 299, 125125
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[5] Devi, A., Anu-Appaiah, K. A. (2020). American Journal of Enology and Viticulture, 71(2), 105-113