Optimised extraction and preliminary characterisation of mannoproteins from non-Saccharomyces wine yeasts

The use of non-Saccharomyces yeast species for the improvement of wine technological and oenological properties is a topic that has gained much interest in recent years. Their application as co-starter cultures sequential to the inoculation of Saccharomyces cerevisiae and in aging on the lees has been shown to improve aspects such as protein stability and mouthfeel.

These contributions have frequently been associated with higher levels of polysaccharides, specifically the cell wall-derived mannoprotein. Furthermore, mannoprotein structure and composition has been shown to vary between yeast strains, which in turn may influence their behaviour in the wine matrix. However, non-Saccharomyces yeasts are typically weak fermentors and are frequently out-competed in the fermentation medium.

An alternative strategy to their use as co-starter cultures is the isolation of the compound of interest for exogenous application to wine. Indeed, the addition of exogenous mannoprotein-containing products derived from the cell wall of the wine yeast S. cerevisiae is a fairly common winemaking practice. Nevertheless, the extraction of mannoproteins from non-Saccharomyces yeasts has not yet been well described.

This study aimed to optimise the extraction of mannoproteins from four non-Saccharomyces strains, and to perform a preliminary investigation into the compositional differences of the mannoproteins obtained from the different species.

Find out which combined methods with varied parameters of ultrasound and enzymatic extraction with β-glucanase to optimise mannoprotein yield were adopted and gave the highest yield of mannoproteins from all species, as well which differences in carbohydrate/protein ratios between species were identified. Is their impact on the carbohydrate/protein ratio in particular an important factor to consider for applications such as wine protein haze reduction and tartrate stabilisation?

Video of the seminar held during Macrowine virtual (June 23-30, 2021)

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