Today, bentonite continues to be one of the most used products to remove proteins in white wines in order to avoid their precipitation in bottles. However, excessive use of bentonite has negative effects on the aroma of final wine, so the optimization of the dose and the time of its application are important for winemakers. This paper analyzes how applying an equal dose of bentonite at different stages (must clarification; beginning, middle, and end of fermentation) affects the macromolecular profile, protein stability, physical-chemical characteristics and aromatic profile of the wine obtained. The results showed the addition during fermentation (especially in the middle and at the end) reduced the total dose required for protein stabilization of Albariño wines and maintained the sensory characteristics of this variety.

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Summary The bentonite use to remove proteins from white wine is a widespread practice that prevents protein haze formation after bottling. However, an excess of bentonite can have negative effects on both the aromatic profile of young white wines and the quality of the foam of sparkling wines. Therefore, the optimisation of bentonite amount to be used and the moment of its application during winemaking to minimise wine quality losses are of great interest for winemakers. This paper analyses how applying an equal bentonite dose at different stages (must clarification; beginning, middle and end of fermentation) on two scales (industrial and pilot) affects the protein content and stability, physical–chemical characteristics, aromatic profile and foam quality of the obtained wines. No important differences in the oenological parameters were observed between industrial and pilot scales, whereas the scale of the experimental treatments affected protein stability, aroma composition and foam quality of the wines.

<p style="text-align: justify;"><strong>Aim</strong>: This work is aimed to study the effectiveness of the use of bentonite at different stages of the vinification process (pilot and industrial scales) in relation to wine protein stability. The effect of wine storage and ageing on protein content and stability is also studied.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The experimental trials were made with a Macabeu wine (vintage 2011) and included the following treatments : bentonite addition to must only, bentonite addition during fermentation (beginning, middle and end), and no treatment (control). The results show no effect of scale in fermentation kinetics. At both scales, the wines treated with bentonite during fermentation had lower total protein concentrations as compared to the control wines (10-17 %) and the wines obtained from must treated with bentonite (7-14 %), which were the most unstable.</p><p style="text-align: justify;"><strong>Conclusion</strong>: This study shows that the fermenter size (industrial and pilot scale) has no significant effects on alcoholic fermentation, indicating that, from a practical point of view, pilot-scale fermentations satisfactorily reproduce those performed at industrial scale. Moreover, all the wines treated with bentonite during fermentation present a lower protein concentration and a higher stability.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results obtained in pilot-scale fermentations are representative of industrial-scale fermentations and therefore can be used reliably to study protein stability and stabilization in white wines.</p>

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