POTENTIAL OF PEPTIDASES FOR AVOIDING PROTEIN HAZES IN MUST AND WINE

Abstract

Haze formation in wine during transportation and storage is an important issue for winemakers, since turbid wines are unacceptable for sale. Such haze often results from aggregation of unstable grape proteinaceous colloids. To date, foreseeably unstable wines need to be treated with bentonite to remove these, while excessive quantities, which are often required, affect the wine volume and quality (Cosme et al. 2020). One solution to avoid these drawbacks might be the use of peptidases. Marangon et al. (2012) reported that Aspergillopepsins I and II were able to hydrolyse the respective haze-relevant proteins in combination with a flash pasteurisation. In 2021, the OIV approved this enzymatic treatment for wine stabilisation (OIV-OENO 541A and 541B).

Herein, we aimed to gain an improved understanding of the influence of this peptidase treatment on the colloids and the quality of must and wine. For this purpose, naturally present colloids were removed from a must and wine by ultrafiltration and replaced by protein-rich, well-characterized must and wine colloids, respectively. Subsequent enzymatic treatments were performed in duplicate on technical scale (ca. 60 L for must, 16 L for wine) by adding two aspergillopepsins separately to the musts and wine followed by a brief heating to 80 °C. Control batches were treated identically, except for enzyme addition. Aliquots (each 30 L) of the treated musts were fermented. The composition and concentration of the colloids in the treated musts and wines were determined chromatographically. Haze forming potential was assessed by the heat test. The influence of the peptidases on the quality of the resulting musts and wines was investigated by sensory trials (triangle tests).

Size exclusion chromatography showed a reduction of the proteins in the musts by the enzyme treatment of about 80% as compared to a 15% reduction for the heat treatment without enzyme. Fermentation of the enzyme-treated musts resulted in stable wines, while the wines from the must without enzyme addition were unstable. The treatment of the wine showed only minor reductions of proteins (19%) in all wines. An effect of the enzyme treatment on the carbohydrates or sensory differences were not observed in comparison to the treatment without enzyme.

In brief, we provide new insights into the influence of the OIV-approved peptidase treatment with aspergillopepsin on colloids and wine quality, which will help achieve greater acceptance from wine makers.