8F Interactions Between Wine Matrix Macro-Components and Aroma Compounds 421
Other methods to determine the interactions between aroma compounds and
wine matrix components do not involve gas phase measurements. For example, the
equilibrium dialysis methodhas been applied for determining interactions between
yeast macromolecules and some wine aroma compounds (Lubbers et al. 1994a) and
more recently to study the interaction of aroma compounds and catequins in aqueous
solution (Jung and Ebeler 2003). While this method can be set up in different ways,
a simple approach is to fill a dialysis cell (two chambers separated by a semiper-
meable membrane) with an aromatizedliquid. A non-volatile component of wine
can be added to one chamber of the cell and then the system allowed to come to
equilibrium. If the added non-volatilecomponent binds the aroma compound, the
other chamber will be depleted by this binding. Quantification of this change in
concentration permits calculating the quantity that is bound to the added substrate.
The above-mentioned methods can be used to demonstrate the existence of
molecular interactions between aroma compounds and other wine macromolecules;
nevertheless, they do not provide any insight into the nature of this interaction.
Determining the nature of an interaction typically involves the use of spectroscopic
methods; unfortunately, this methodology has not been extensively applied to study-
ing wine flavour interactions.
Among the few works published determining mechanisms of flavour interactions
in wines, the work of Dufour and Bayonove (1999b) is notable in that they studied
the interactions between wine aroma compounds and polyphenols using exponential
dilution analysis and H-1 NMR spectroscopy. They calculated the dissociation con-
stants confirming the weak capacity of catequins to bind aroma compounds. Jung
et al. (2000) also used NMR techniques to explore the mechanisms of interaction
between some typical winepolyphenols (gallic acid and naringin) and two aroma
compounds (ethyl hexanoate and 2-methylpyrazine).
8F.2 Interactions Between Aroma Compounds and Specific
Wine Matrix Components
8F.2.1 Wine Matrix Composition
Wine is a complex mixture consisting of indigenous components and those obtained
by chemical and biochemical transformations by wine microorganisms and/or dur-
ing wine aging. Wine composition varies widely and is influenced by the grape
(variety, quality) and by the winemaking conditions.
Many of the wine macro-components (e.g. carbohydrates, proteins, polyphe-
nols), come from the skins and the pulp of grapes and from the cell walls of
the yeast. Although this varies, the molecular weight of the majority of macro-
molecules is over 10,000 D and their final concentration ranges from 0.3 to 1 g/L
(Voilley et al. 1991). Most macromolecules will be eliminated by clarification and
stabilization treatments of the wine. Because of their interactions with wine aroma