9D Influence of Phenolics on Wine Organoleptic Properties 559
In general, the effectiveness of carbohydrates to prevent protein-tannin aggregation
increase with their ionic character (Luck et al. 1994; Carvalho et al. 2006b; de Fre-
itas et al. 2003): neutral carbohydrates practically do not affect aggregation.
Ionic polysaccharides are present in wine, and are expected to affect mouth
feel properties and mainly astringency acting on the interaction between tannins
and salivary proteins. The major wine polysaccharides are arabinogalactan proteins
(AGP) and rhamnogalacturonan II (RGII), pectic polysaccharides which originate
from grape cell walls, and mannoproteins (MP) produced by yeast during wine
fermentation (Doco et al. 2000). Vidal et al. (2004c) have demonstrated that pro-
cyanidin astringency decreases in the presence of RGII, while MPs and AGPs
decrease bitterness (Vidal et al. 2004c). Escot et al. (2001) have demonstrated
that the wine structure was modified by the addition of mannoproteins and that
this addition reduces astringency of redwine due to a higher tannin/mannoprotein
condensation level.
Recently, Carvalho et al. (2006b) studiedthe influence of wine polysaccharides
(AGP, RGII and MP) on salivary protein-tannin interactions. The results showed that
the most acidic fractions of AGPs and MPs have the ability to inhibit the formation
of aggregates between condensed tannins and two different salivary proteins ( -
amylase and IB8c). The concentrations tested are below to those present in wine
which means that they could have an influence in wine astringency.
On the other hand, it has also been foundthat polysaccharides present in wines
interfere with the self-aggregation of proanthocyanidins (Riou et al. 2002). The
change in the proanthocyanidin colloidal state in wines could also affect their ability
to complex with salivary proteins and thereby their sensory properties.
9D.3.7 Experimental Studies of the Interactions Between Proteins
and Tannins, and Astringency
Beside sensorial analysis, several other experimental techniques have been used to
study the interaction between tannin and proteins, a characteristic that is involved
in astringency. The development of new techniques that only require small amounts
of compounds, the elucidation of new polyphenol structures and proteins engaged
in astringency perception, and the improvement of the preparative techniques to
isolate these compounds have contributed importantly to the advances in this field.
These techniques include NMR, microcalorimetry, enzyme inhibition, microscopy
techniques, radioactivity measurements, HPLC, fluorescence, electrophoresis, ESI-
MS, infrared spectroscopy, marker utilization, molecular modeling and light scat-
tering measuring techniques such as dynamic light scattering (DLS) and neph-
elometry (Chapon 1993; de Freitas and Mateus 2002; Edelmann and Lendl 2002;
Hagerman and Butler 1980; Sarni-Manchado and Cheynier 2002; Beart et al.
1985; Kandra et al. 2004; Papadopoulou et al. 2005; Soares et al. 2007; Con-
delli et al. 2006; Kallithraka et al. 1998; Siebert et al. 1996; Simon et al. 2003;
Wroblewski et al. 2001).