Wine Chemistry and Biochemistry

8F Interactions Between Wine Matrix Macro-Components and Aroma Compounds 425

More recently, Le Berre et al. (2007) observed reduced volatility of whisky

lactone in hydroalcoholic solution compared to that in water, but not for isoamyl

acetate. The same authors found a synergic effect of the woody note on the fruity

odour in the aqueous solution, which disappeared with the addition of ethanol. They

also observed that the woody note (for the highest woody odour concentrations) was

masked by the fruity odour, in both aqueous and dilute alcohol solutions.

8F.2.2.2 Phenolic Compounds

Polyphenols, major non-volatile components in wine, have been reported to interact

non-covalently with aroma compounds in solution. These interactions could affect

the release of wine aroma compounds. Some of the changes in wine flavour result-

ing from using different grapes or wine making practices may in fact be due to the

effect of these factors on the composition of the polyphenol fraction. For example,

the removal of polyphenols through filtration or fining treatment and precipitation

induced by increasing polymerization during wine aging has been suspected to pro-

duce flavour balance modifications (Voilley et al. 1991).

Early studies carried out by King and Solms (1982) documented interactions

between phenolic compounds and aroma compounds in water systems. They sug-

gested that hydrophobic interactions between aroma compounds and phenolic com-

pounds increased solubilityof aroma compounds thereby decreasing the activity

coefficient of the aroma compounds.

Using exponential dilution analysis and an NMR technique, Dufour and

Bayonove (1999) confirmed the existence of weak interactions between catequins

and aroma compounds in model wine systems and they also agreed that mutual
hydrophobicity was the driving force for this interaction. They also showed a differ-

ent type of interaction depending on the type of polyphenols (catequin or tannin),

and on the nature of the aroma compound.

There is substantial literature reporting the reaction of aldehydes (mainly acetal-

dehyde) with wine polyphenols such as flavanols and anthocyanidins (Fulcrand

et al. 1996; Dallas et al. 1996; Saucier et al. 1997; Timberlake and Bridle 1976;

Escribano-Bail ́on et al. 1996; Es-Safi et al. 1999,etc.). One of these reactions

involves a Bayer acid-catalyzed condensation, giving rise to a condensation product

composed of two flavanols, two anthocyanidins, or one flavanol and one anthocyani-

din linked by an ethanolic bridge (formed from an aldehyde). A second type of

reaction involving aldehydes is produced by adding the aldehyde to the anthocyanin

molecule, forming an additional ring in theanthocyanin. All of these condensation

products are directly related to the development of color and astringency during

wine aging (Fulcrand et al. 1996; Atanasova et al. 2002; Mateus et al. 2002, etc.).

This condensation mechanism could explain why Escalona et al. (2001) found that

the flavanol (+)-catequin in hydroalcoholic solution (10–20 mL/100 mL) had little

effect on the activity coefficient for ethyl hexanoate while octanal was significantly

affected.

Recently Nonier et al. (2007) studied the reaction kinetics at different pH (3 and

3.5) of (+)-catequine and representative oak wood furans (furfuraldehyde [FA],