Odor-active Compound Adsorption onto Bentonite in a Model White Wine Solution

The mechanisms and occurrence of aroma depletion during wine fining is still not clear. Previous results of our group led to hypothesized that some odor-active compounds were removed through direct adsorption mechanism on the clays without the involvement of any wine macromolecules. This paper examined the adsorption isotherms at 17±1 °C of some volatile compounds, principally responsible of the fruity character of white wines, onto three bentonite samples. The bentonites were added in three different amounts to a model white wine “spiked” with eight odor-active compounds and in the absence of wine macromolecule. The elemental composition, the surface charge density, and the SSA of the clays were determined and differences were analyzed by Tukey’s test. The Langmuir and the Freundlich models were fitted to the adsorption data. The most experimental adsorption isotherms were robustly fitted by the Freundlich equation and evidenced differences in the adsorption intensity and capacity values for the tested odor- active compounds. The main interaction forces controlling adsorption appeared to be related more to the clay characteristics, than to the compounds properties: samples having a lower SSA value and a greater charge density per surface unit seemed to interact with most of the odor-active compounds primarily through physical mechanisms. Differently, the clay with a large SSA value and a low charge density per surface unit promoted stronger adsorptions that were probably driven also by chemical interactions especially for ethyl esters.