Colloidal color stabilization in wine: A comparative study of Saccharomyces and non-Saccharomyces mannoproteins

Abstract

Structure-function relationships between the polysaccharide part of S. cerevisiae Mannoprotein Pools (MPs) and their potential to interact with anthocyanins and Protein-Tannins aggregates was previously assessed [1,2]. Herein, MPs from nine yeast strains including Saccharomyces and non-Saccharomyces species were evaluated by their potential to stabilize Colloidal Coloring Matter (CCM) of red wines. β-glucanases extraction procedure preserved mannoproteins native structure to their uttermost extent. The strains comprised a wild-type (MP-WT) S. cerevisiae strain and its mutants ΔMnn2 (MP-Mnn2) and ΔMnn4 (MP-Mnn4) – linear N-glycosylated backbone and absence of mannosyl-phosphate groups, respectively; non-Saccharomyces strains of 3 different species: Hanseniaspora vineae (MP-Hv), Torulaspora delbrueckii (MP-Td), and Schizosaccharomyces japonicus (MP-Sj) all grown in anaerobiosis; and three enological Saccharomyces cerevisiae strains grown in different metabolic conditions: MP-C1 (anaerobiosis), and MP-IC1 and MP-IC2 (aerobiosis). MPs colloidal stabilization properties were evaluated at first by their capacity to stabilize K₄[Fe(CN)₆] (Prussian Blue) in presence of CaCl₂ [3], then by their capacity to inhibit turbidity increases (ΔNTU) of young Merlot and oxidized Marselan wines stored for 2 days at 4 °C. Wine samples after cold test were centrifuged and the color parameters of the supernatant were assessed.

Prussian blue control samples lost complete absorbance at 750 nm 24 hours after CaCl₂ addition at 0.8 g.L_-1. MP-Sj and MP-IC2 accelerated blue color loss. Other MPs had a stabilization effect whose efficiency depended on the MP. MP-Mnn2/MP-Mnn4 stabilized 90-100% of color followed by MP-Hv/MP-WT (~80%), and MP-C1/MP-IC1 (~60%). Increases in MP concentration did not systematically led to an increase in stability, which indicates that several physico-chemical interactions were taking place simultaneously.

Concerning the stability tests in real wine conditions, MP-Sj and MP-IC2 had the same effect as in model conditions (Prussian blue) while, the positive impact on colloidal stability was dependent on the wine matrix and MP concentration. In Marselan wines, MPs had a mild impact on ΔNTU at concentration of 1 g.L_-1 whereas in Merlot wines, at the same concentration, MP-Hv, MP-Td, and MP-IC1 reduced ΔNTU of 2 to 3-fold in comparison with control samples.

Associated with the characteristics of each MP polysaccharide moiety, our findings help discover the interaction mechanisms involved in CCM and how MPs can improve its stability. The net negative charge of mannoproteins seems to have a negative impact on color stability. Other molecular characteristics counter-balance this instability effect such as compactness and the protein mass percentage.

References

[1] Assunção Bicca, S., Poncet-Legrand, C., Williams, P., Mekoue, J., Doco, T., Vernhet, A. (2022). Carbohydrate polymers, 277. https://doi.org/10.1016/j.carbpol.2021.118758

[2] Assunção Bicca, S., Poncet-Legrand, C., Roi, S., Mekoue, J., Doco, T., Vernhet, A. (2023). Food Chemistry, 422. https://doi.org/10.1016/j.foodchem.2023.136160

[3] Michaël, N., Apolinar-Valiente, R., Iturmendic, N., Williams, P., Doco, T., Moine, V., Massot, A., Jaouen, I., Sanchez, C. (2019). Food Hydrocolloids, 97. https://doi.org/10.1016/j.foodhyd.2019.105176