456 M. Monagas and B. Bartolom ́e
charcoal but that the adsorption mechanism is based on weak and reversible interac-
tions. The adsorption capacity of yeast cell was limited by the partition equilibrium
between the anthocyanins to be adsorbed and the fraction remaining free in solution
and at the same time was affected by the temperature, anthocyanin initial content
and concentration of yeast lees employed. The amount of anthocyanin adsorbed
was also influenced by the ethanol concentration, SO 2 , pH and pigment structure
(Vasserot et al. 1997). Anthocyanins were absorbed in proportion to their polar-
ity as follows: delphinidin>cyanidin>petunidin>peonidin>malvidin. In contrast,
Mazauric and Salmon (2005), by analyzing the remnant polyphenols in the medium
in experiments carried out in model wine solution, recently found that the adsorption
of anthocyanins on yeast lees was unrelated to their polarity. Desorption experiments
indicated that the acetyl derivatives remained more adsorbed than the remaining
ones (Mazauric and Salmon 2006). These findings were partly in accordance with
the results obtained in a recent study performed in model solutions with fresh yeast
(Medina et al. 2005). Morata et al. (2003, 2005) demonstrated that the yeast strain
largely influenced the anthocyanin adsorption capacity of yeast cell walls during
fermentation ofV. viniferaCabernet Sauvignon and Graciano musts. However, in
contrast to the results obtained by Vasserot et al. (1997) on yeast lees, the less polar
acylated anthocyanins, in particular the cinnamoyl derivatives were more strongly
adsorbed than the more polar non-acylated ones on the cell walls of fermenting
yeasts. Discrepancies between these studies could be attributed to the use of model
solutions vs must and to different physiological status of the yeast used in the
experiments.
AcknowledgmentsThe authors are grateful to the AGL2006-04514 project (Ministerio de Edu-
caci ́on y Ciencia) for financial support of this work.
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