Re-investigation of the relevant factors affecting quantitative precipitation of wine polysaccharides: A GC-MS and HRSEC-RI characterization study using central composite design and response surface methodology.

Wine polysaccharides are abundant and complex macromolecules that influence wine's colloidal stability and quality. Although several precipitation methods have been proposed for their quantification, optimal conditions for quantitative recovery have not yet been systematically evaluated using central composite design and response surface methodology. In this study, six constitutional monosaccharides were quantified by gas chromatography-mass spectrometry to assess the effects of sample concentration, precipitation time, precipitation agent composition and their interactions on wine polysaccharide recovery, while high-resolution size-exclusion chromatography with refractive index detection complemented this assessment by providing polymer distribution data. All quadratic models were highly significant (p < 0.0001) and showed good predictive performance. Precipitation time had no significant effect, whereas moderate sample concentration coupled with mildly acidified ethanol enhanced the recovery and analysis of rhamnogalacturonans and polysaccharides rich in arabinose and galactose. Mannoproteins precipitated efficiently even in highly acidified non-concentrated samples, whereas galacturonic acid exhibited an opposite trend, indicating that homogalacturonans may require specific and less common conditions for full recovery. This work allowed a partial optimisation, highlighting the potential need for multi-step protocols to recover the full spectrum of wine polysaccharides.