244 M. Luz Sanz and Isabel Mart ́ınez-Castro
in equilibrium with gluconic acid, and represent 5.8% and 4.1% of the acid level,
respectively (Barbe et al. 2002).
The origin of glucuronic, galacturonic, 5-oxogluconic and 2-oxogluconic acids
in musts and wines was showed by Sponholz and Dittrich (1985). They compared
healthy andBotrytis cynereainfected products and found that the production of
sugar acids was proportional to the number of infected berries. Application of pure
cultures demonstratedthat acetic bacteria (Gluconobacter oxydansandAcetobacter
xylinum) produced most of the sugar acids found in botrytized wines.
Sugar acids have been related to the binding of SO 2 in wines (Ribereau-Gayon
1973); gluconic acid appeared to be indirectly responsible for about 8% of the bind-
able SO 2 in musts from botrytized grapes (Barbe et al. 2002).
The presence of mucic acid in wine causes calcium mucate crystals which are
formed during prolonged storage when wine contains>0.1 g/L mucic acid. This
level is reached when 10–25% of the grapes used are infected withB. cinerea
(Wuerdig 1977).
7.7 Polysaccharides
Increased attention has been paid in the last few years to the study of polysaccha-
rides in wine and great advances in the knowledge of their structures and intrinsic
properties have been achieved (Vidal et al. 2003; Ayestar ́an et al. 2004).
Polysaccharides are considered those carbohydrates with a degree of polymer-
ization higher than 20. Their presence in wines is due to the contribution of the
cell walls of either microorganisms during alcoholic fermentation or grape berries
after degradation by pectic enzymes during grape maturation or during winemaking.
Polysaccharides constituteone of the main groups of macromolecules in wine and
contribute to increase its viscosity and stability. Moreover, polysaccharides have
been linked to the organoleptical qualities of wines (Vidal et al. 2003) because
their interactions with other constituents such as polyphenols (Riou et al. 2002),
aromatic compounds (Chalier et al. 2007), etc. The main polysaccharides coming
from berries cell walls (pectic polysaccharides) are rhamnogalacturonans II (RG-
II; Pellerin et al. 1996) and arabinogalactan-proteins (AGPs; Brilloue et al. 1990)
whereas those from yeast cell walls are mainly mannoproteins (MPs) and mannans
(Waters et al. 1994).
After their isolation by chromatographic techniques (anion-exchange chromatog-
raphy, size exclusion, etc.), different analytical methodologies have been used
to identify and quantify the polysaccharides in wine; the most commonly used
being the traditional methylation analysis followed by GC-MS (Doco and Bril-
louet 1993). Polysaccharides have also beendetermined after solvolysis with anhy-
drous methanol containing HCl by GC-MS of their per-O-trimethylsilylated methyl
glycosides (Vidal et al. 2003). Other techniques such as Fourier transform infrared
spectroscopy (FTIR) have been more recently proposed (Coimbra et al. 2002, 2005;
Boulet et al. 2007).