306 M.S. P ́erez-Coello and M.C. D ́ıaz-Maroto
formation of their corresponding alcohols and ethyl esters. On the other hand, oak
lactone, furfural, and ethylphenol contents increase, and the concentrations of still
other components like furfuryl alcohol and guaiacol do not change very appreciably
(P ́erez-Prieto et al. 2003). The increase of furfural during bottle aging has been
previously observed, since it does not originate exclusively from oak but can also be
formed from other hexoses and pentoses in the wine (Schreier 1979; P ́erez-Coello
et al. 2003).
8C.5 New Trends in Wine Aging
Oak barrel aging present some inconveniences, such as the high price of barrels,
the amount of time the wine has to be left in the barrels before it can be brought
to market, monitoring of the wine during aging, and others. This is especially true
for white wines, because oxygenation through the pores in the wood is undesirable
for these wines. Depending on the extraction conditions, results similar to those
achieved by conventional barrel aging can be achieved using oak chips and relatively
short contact times (Wilker and Gallander 1988).
Just a few years ago the use of oak chips was legal only in certain non-European
countries. However, for the reasons just stated, the European Commission has pro-
vided for the use of oak chips in the production of wines, obligating producers who
want to use this technique to write it in the labels (Regulation N. 1507/2006 of
October 11th, 2006). The said resolution has, nonetheless, given rise to additional
difficulties connected with wood chip use, namely, different oak origins, different
chip sizes, and different processing methods, all of which only increases the vari-
ability in the volatiles composition already observed in barrel aging, especially since
oak chip production is not standardized (Ducournau et al. 1999).
Oak chips were first used for white wines, to which they were added during
fermentation or afterwards, during a short period of aging. This method appears to
hold out special promise for neutral grape varieties with weak floral or fruity aro-
mas. Using wood chips imparts “oak”, “spicy”, and “vanilla” aromas to the wines,
improving their sensory impressions. Additionally, compared with barrel aging,
the fruity attributes intrinsic to the grape variety used are still expressed by the
wines, because the volatile components do not undergo oxidation while the wines
are in contact with the wood chips (Wilker and Gallander 1988; Guti ́errez Afonso
2002).
Fermentation rates have been observed to increase when fermentation is carried
out in the presence of wood chips, presumably because the oak chips act as carriers
for the yeasts, resulting in the formation of higher quantities of acetates and fatty
acid esters, which may help impart a morefruity aroma to wood chip-treated wines
(P ́erez-Coello et al. 2000b).
Wood chips are ordinarily used in amounts ranging between 2g/L and 8g/L for
white wines. Higher quantities cause the wines to lose consumer appeal because of
the intensity of the wood attributes (P ́erez-Coello et al. 2000a).