Abstract
Nowadays commercial preparations of yeast polysaccharides (PSs), in particular mannoproteins, are widely used for wine colloidal and tartrate salt stabilization. In this context, the industry has developed different processes for the isolation and purification of PSs from the cell wall of Saccharomyces cerevisiae. This yeast releases limited amounts of mannoproteins in the growth medium, thus making their direct isolation from the culture broth not economically feasible. On the contrary, Schizosaccharomyces japonicus, a non-Saccharomyces yeast isolated from wine, releases significant amounts of PSs during the alcoholic fermentation. In the present work, PSs released by Sch. japonicus were recovered from the growth medium by ultrafiltration and their impact on the wine colloidal stability was evaluated. Interestingly, these PSs contribute positively to the wine protein stability. The visible haziness of the heat-treated wine decreases as the concentration of added PSs increases. Gel electrophoresis results of the haze and of the supernatant after the heat stability test are consistent with the turbidity measurements. Moreover, particle size distributions of the heat-treated wines, as obtained by Dynamic Light Scattering (DLS), show a reduction in the average dimension of the protein aggregates as the concentration of added PSs increases.
Highlights
The use of bentonite represents the most common method used worldwide for wine protein stabilization [1]
Due to the negative implications associated with bentonite, several alternatives to its use have been explored such as flash pasteurization [5,6], ultrafiltration [7,8], addition of proteolytic enzymes [9,10]
These results are in agreement with those previously observed with Sch. japonicus # UCD2489 during the alcoholic fermentation carried out using the same synthetic grape juice but containing a higher sugar concentration (220 g/L) [51]
Summary
The use of bentonite represents the most common method used worldwide for wine protein stabilization [1]. Bentonite acts as a cation exchanger and, by binding to proteins present in the wine through electrostatic interactions, forms complexes that can be removed by filtration. Silica gel, hydroxyapatite and alumina [11], zirconium oxide [12,13,14,15], natural zeolites [16,17], chitin and chitosan [18,19,20,21], carrageenan [22,23,24], and yeast mannoproteins [25,26,27,28,29,30] These last ones have recently found an increasing interest in the wine industry as a result of the multiple positive effects associated
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