MONOSACCHARIDE COMPOSITION AND POLYSACCHARIDE FAMILIES OF LYOPHILISED EXTRACTS OBTAINED FROM POMACES OF DIFFERENT WHITE GRAPE VARIETIES
The recovery of bioactive compounds from grape and wine by-products is currently an important and necessary objective for sustainability. Grape pomace is one of the main by-products and is a rich source of some bioactive compounds such as polyphenols, polysaccharides, fatty acids, minerals and seed oil. Polysaccharides contained in the grape cell wall can be rhamnogalacturonans type II (RG-II), polysaccharides rich in arabinose and galactose (PRAG), mannoproteins (MP), homogalacturonans (HG) and non pectic polysaccharides (NPP). The aim of this study was to evaluate the monosaccharide composition and polysaccharide families of extracts obtained from pomaces of different white grape varieties.
Twelve grape pomaces from 9 different white grape varieties of Castilla y León region were analysed after destemming and pressing the grapes. The polysaccharide extraction was carried out with the method previously developed by Canalejo et al. (2021). The lyophilised extracts were analysed by gas chromatography with mass spectrometry detector following the conditions developed by Guadalupe et al. (2012). An ANOVA and a principal component analysis (PCA) were carried out to determine the differences between grape varieties using the RStudio program.
Statistically significant differences were found between the white grape pomaces studied and even within the same grape variety. The Verdejo and Puesta en Cruz varieties showed the highest polysaccharide content due to the highest content in glucose and galacturonic acid. In addition, the Puesta en Cruz variety stood out for its higher rhamnose and galactose content. On the other hand, the Viura grape variety with highest maturity degree and the Sauvignon Rytos presented the lowest polysaccharide concentration. Considering the percentage of the different polysaccharide families, the PCA selected two components with an eigenvalue greater than 1, which explained 92.3% of the total variance. The Verdejo, Viura, Rufete Serrano and Soreli were more associated to the percentage of NPP, while the Malvasía, Puesta en Cruz and Sauvignon Blanc were more correlated with the HG and PRAGs.
ACKNOWLEDGEMENTS: The authors would like to thank the Agencia Estatal de Investigación (AEI) and the Ministerio de Ciencia e Innovación (MICINN) for the funding provided for this study through the project PID2021-123361OR-C21 (with FEADER funds). M. C-F. also thanks the MICINN and AEI for funding her predoctoral contract (PRE2020-094464, with FSE funds).
Issue: OENO Macrowine 2023
Contact the author*
white pomace, monosaccharides, grape polysaccharides, by-products