Characterization and emulsifying properties of extracts obtained by physical and enzymatic methods from an oenological yeast strain.

Background: Glycosylated compounds are one of the main fractions of the yeast cell wall. Thanks to their amphiphilic structure, they have been studied as stabilizers in food emulsions over a broad range of pH conditions with encouraging results. Nevertheless, extraction costs still represent an important limit for their application in the food industry.

Results: In this research, four extraction methods were applied to yeast cells exploiting both physical (heating and sonication) and enzymatic approaches (use of three industrial enzyme preparations, namely Glucanex®, Sur Lies and Elevage). A fifth method involving a pure β-glucanase enzyme (Zymolyase) was taken as reference. These extraction methods were applied to the oenological strain Saccharomyces cerevisiae EC1118, and their extraction yields and chemical properties (quantitative and qualitative determination of sugars and proteins) were studied. Emulsifying activities were determined at three different pH values (3, 5 and 7). Extractions with Physical, Glucanex and Sur Lies methods were the most successful approaches to obtain relevant amounts of yeast compounds with good emulsifying activities for 2:1 oil-in-water emulsions at pH 3 and 7 over 48 h.

Conclusions: These results indicate that there is the potential for the extraction approaches here proposed to become viable tools for the recovery of yeast compounds to be used as emulsifiers in foods. This approach can be considered as the starting point to explore the possibility to exploit yeast by-products from the fermentation processes (e.g. fermentation lees from wine and beer making) as valuable compounds for food applications. © 2019 Society of Chemical Industry.