The organoleptic properties of red wine are among the essential wine quality parameters. Besides volatile aroma compounds, the nonvolatile has seen a growing interest in the last decades, comprising taste molecules as well as substances evoking a broader range of mouthfeel sensations. The influence of polysaccharides on wine organoleptic qualities is associated with their ability to interact and aggregate with tannins and to decrease perceived tannin astringency in wine. Also, wine polysaccharides have been shown to interact with aroma compounds. The interaction of polysaccharides with tannin and aroma compounds depends on the polysaccharides’ chemical structure and composition. This work aims to isolate and characterize polysaccharides from Pinot noir wine and study their interaction with wine aroma compounds.
From yeast, polysaccharides were sequentially extracted with hot water (20% yeast cells aqueous solution, 121°C, 3.5 h) and alkali (3% sodium hydroxide solution, 80°C, 6 h). Grape polysaccharides were isolated from Pinot noir grapes with hot water (90℃, 2 h) and alkali solution. Polysaccharides in wine were obtained via membrane ultrafiltration with molecular weight cut-off of 2-100 kDa and over 100 kDa. All the polysaccharides were precipitated with ethanol and dried under a vacuum oven.
The isolated polysaccharides were analyzed for purity, and all isolated polysaccharides have high purity. The polysaccharides isolated from yeast have the highest purity. Size exclusion liquid chromatography was used to analyze the isolated polysaccharides’ molecular distribution. Matrix-assisted laser desorption/ionization and time-of-flight mass spectrometry (MALDI-TOF) was used for partial sugar sequencing.
The sugar composition of the isolated polysaccharides was analyzed by gas chromatography and gas chromatography-mass spectrometry after derivatization. The results showed that sugar composition differed greatly depending on the polysaccharides’ source and the methods used for polysaccharide isolation. Water extracted polysaccharides from yeast mainly consist of mannose, glucose, xylose, and alkali extracted yeast polysaccharides mainly consisting of mannose and glucose. In comparison, water extracted grape polysaccharides are mostly glucose, arabinose, rhamnose, galactose, mannose, galacturonic acid, and xylose. Alkali extracted grape polysaccharides are composed primarily of arabinose, galactose, glucose, rhamnose, galacturonic acid, xylose, and mannose. The polysaccharides isolated from the wine with molecular weight 2- 100 kDa are composed mainly of galacturonic acid, mannose, rhamnose, glucose, galactose, and arabinose. Polysaccharides with a molecular weight of over 100 kDa are composed mainly of arabinose, mannose, galactose, rhamnose, galacturonic acid, and glucose.
Our next step is to understand how the sugar composition, structure, molecular weight will interact with wine aroma compounds and alter aroma perception.