Aim: The aim of this study was to investigate the performance of ultrafiltration (UF) membranes to achieve a selective separation of macromolecules from Sauvignon blanc wine into stable and unstable fractions and to characterize the main compounds separated.
Methods and results: The macromolecules from two Sauvignon blanc wines (Curicó Valley and Casablanca Valley, Chile) were separated by a cascade of UF membranes into three nominal fractions (10-30, 30-100 and 100-300 kDa). These fractions were characterized by native and SDS electrophoresis and membrane performance was evaluated by protein rejection and transmission. Separation by UF allowed the concentration of thermally unstable proteins in the 10-30 kDa retentate fraction, increasing heat induced haze by 8.9 fold, while heat stable glycoproteins were concentrated into the 100-300 kDa retentate fraction, reducing heat induced haze by 5.3 fold compared to unfiltered wine. The retention of high macromolecular species by the UF membrane with a 100 kDa molecular weight cut-off contributed to increased protein aggregation in the filtered wines.
Conclusion: The concentration and purification of anti-hazing compounds by membrane filtration seem to be a new technology to improve the protein stability of white wines.
Significance and impact of the study: Specific wine proteins are responsible for wine instability, resulting in haze formation in white wines. On the other hand, glycoproteins prevent protein aggregation and precipitation, thereby improving wine stability. Fractionation of wine macromolecules by UF membranes may help us to improve our knowledge about the contribution of specific proteins and glycoproteins to the haze stability of white wines.
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