Danye Zhu, Armando Alcazar Magana, Yongsheng Tao, and Michael. C. Qian*
*Oregon State University, 100 Wiegand Hall, Corvallis, OR 97331 (michael.qian@oregonstate.edu)

Polysaccharides are the main macromolecule components in wine. Polysaccharides are of interest because they can interact with wine aroma and flavor compounds to affect sensory quality. The primary polysaccharides in wine are derived from yeasts and grapes. Understanding the structural characterization of polysaccharides from different sources is extremely important for wine organoleptic quality. In this study, the sugar composition, molecular weight, and other physicochemical properties of polysaccharides were characterized systematically. Polysaccharides from Saccharomyces cerevisiae (RC 212) were sequentially extracted with hot water (20% yeast cells aqueous solution, 121°C, 3.5 hr) and alkali (3% sodium hydroxide solution, 80°C, 6 hr), named Y1 and Y2. The mixtures were centrifuged and the precipitates were extracted again. The obtained supernatants were neutralized, concentrated, and centrifuged again to remove any precipitates. Absolute alcohol was added to the supernatants overnight to precipitate polysaccharide. The polysaccharides were harvested and dried under vacuum. Sugar purity was analyzed. The polysaccharides were measured using a phenol-sulfuric acid assay and the results showed high purity for isolated yeast polysaccharides. Size exclusion liquid chromatography was performed using an Agilent 1100 liquid chromatography coupled to a RID detector operated in positive polarity. Separation was performed at 30°C in a Superde 200 increase 10/300 (10mm × 300 mm) GL column. Certified polysaccharides standards (1, 5, 25, 50, 150, 270, 410, and 670 KDa) were used for molecular weight calculation. The sugar com- position of polysaccharides was analyzed by gas chromatography-mass spectrometry after metholysis (0.5 M HCl/MeOH at 85°C for 18 hr) and silylation 1-(trimethylsilyl) imidazole (TMSI). Structural characterization results showed polysaccharides vary greatly in composition. Y1 was composed mainly of mannose, glucose, and xylose; Y2 was composed mainly of mannose and glucose.

Funding Support: American Vineyard Foundation (AVF)