Abstract
The diversity of procedures used for the analysis of polysaccharides in musts obtained at laboratory scale did not allow their accurate quantification and characterization. Soluble polysaccharides have been isolated from musts at the initial time of preparation of Sauvignon blanc and Ugni blanc cultivars and the influence of the mode of preparation has been investigated. Heat treatment, commonly used for the inactivation of endogenous glycosylhydrolases, led to an overestimation of polysaccharide contents. Consequently, the characterization of must polysaccharides requires their isolation from crushed and pressed grapes, a procedure representative of the typical process used for white winemaking. Glycosyl residue, determined by GC of their per-Otrimethylsilylated methyl glycosides, and glycosyl linkage, determined by GC of their partially methylated and carboxyl-reduced alditol acetates, composition analyses showed that polysaccharides were a complex mixture of pectic (galacturonans, type I and II arabinogalactans, arabinans), cellulosic and hemicellulosic (xyloglucans and mannans) polysaccharides. Type II arabinogalactan proteins, which are soluble proteoglycans, are the most abundant polysaccharides, whereas the others, that are structural components of cell walls, are present in lower amounts. The significant difference concerning the polysaccharide composition of musts and wines is discussed. Furthermore total polysaccharides were separated in calcium- and ethanol-precipitated polysaccharides. Their respective glycosyl-composition analyses, determined by GC of their per-O-trimethylsilylated methyl glycosides, revealed that neutral "gums" and acidic "pectins" could not be separated by specific precipitation.
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Claims 5
Claim · model-written summary
Heat treatment overestimated polysaccharide content.
Not reportedComparator
Verbatim
e0“Heat treatment, commonly used for the inactivation of endogenous glycosylhydrolases, led to an overestimation of polysaccharide contents.”
e1“crushed and pressed grapes”
Claim · model-written summary
Must polysaccharides comprised pectic, cellulosic and hemicellulosic polysaccharides.
Verbatim
e0“polysaccharides were a complex mixture of pectic (galacturonans, type I and II arabinogalactans, arabinans), cellulosic and hemicellulosic (xyloglucans and mannans) polysaccharides.”
e1“crushed and pressed grapes”
Claim · model-written summary
Type II arabinogalactan proteins were the most abundant must polysaccharides, while other structural polysaccharides were less abundant.
Verbatim
e0“Type II arabinogalactan proteins, which are soluble proteoglycans, are the most abundant polysaccharides, whereas the others, that are structural components of cell walls, are present in lower amounts.”
e1“crushed and pressed grapes”
Claim · model-written summary
Specific precipitation did not separate neutral gums from acidic pectins.
- Taxon
- grapese1
- Treatment
- specific precipitatione0
- Outcome
- neutral "gums" and acidic "pectins" could not be separatede0
- Comparator
- neutral "gums" and acidic "pectins"e0
Not reportedDirection
Verbatim
e0“neutral "gums" and acidic "pectins" could not be separated by specific precipitation.”
e1“crushed and pressed grapes”
Claim · model-written summary
The authors recommend isolating polysaccharides from crushed and pressed grapes to characterize must polysaccharides.
Verbatim
e0“the characterization of must polysaccharides requires their isolation from crushed and pressed grapes”
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