Effect of bentonite fining during fermentation on protein content in Macabeu wines: Comparison of pilot- and industrial-scale experiments

Aim: 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. Methods and results: 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. Conclusion: 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. Significance and impact of the study: The results obtained in pilot-scale fermentations are representative of industrialscale fermentations and therefore can be used reliably to study protein stability and stabilization in white wines.