Exploring the behavior of alternatives to montmorillonite clays in white wine protein stabilization

Abstract

Visual clarity in wines is crucial for commercial purposes [1]. Potential protein haze in white wines remains a constant concern in wineries, commonly addressed using bentonite [2]. Despite its effectiveness, bentonite’s lack of specificity leads to several drawbacks [3], including negative impacts on aroma and phenolic compounds, product loss due to sludge formation after treatment [4], and health and safety concerns related to its production [5]. Thus, interest in alternatives to bentonite has grown in recent decades. In this study, we tested for the first time two alternative clays (sepiolite and palygorskite), comparing their effects, at an equivalent stabilizing dose, with two commercial bentonites and an experimental montmorillonite. The comparison was based on deproteinizing capacity (assessed via protein quantification using HPLC), basic parameters, CIELab color coordinates, volatile organic compounds (VOCs) analyzed by GC-MS, and phenolic compounds (assessed via spectrophotometric indexes) in a white wine from cv. ‘Moscato bianco’. The required stabilization dose with commercial bentonites and experimental montmorillonite was 10 g/hL, while the tested clays needed a sixfold higher dose. No significant differences were observed in pH, whereas slight differences were detected in total acidity. Regarding color, all treatments decreased absorbance at 420 nm compared to the control, except for one commercial bentonite. Significant differences were found among products, with the tested clays showing the lowest absorbance value. Although significant differences were found in CIELab coordinates, none of the treatments led to visual differences compared to the control. Among the 54 detected VOCs, only ethyl butanoate, methyl decanoate, octyl acetate, and dodecanoic acid showed significant differences, with no consistent trend. These results confirm that bentonite does not affect varietal compounds (terpenes and C₁₃-norisoprenoids), and that, at low doses, its negative effects on VOCs are minimal [6]. All treatments significantly reduced the total polyphenols index (TPI) compared to the control. Notably, a highly significant correlation (r² = 0.63) was found between removed proteins and the decrease in TPI, confirming protein-mediated phenolics removal [7].

These results highlight the challenges of finding viable alternatives to bentonite and suggest that bentonite, when used at low doses, can stabilize white wine without compromising its qualitative traits.

References

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