Effect of Bentonite Fining on Odor-Active Compounds in Two Different White Wine Styles

Abstract

Bentonite fining is commonly used in the wine industry as a clarifying technique to remove proteins that are a potential source of haze in wines. Because of mutual flocculation with positively charged hydrocolloids and adsorption, bentonite interacts not only with proteins, but also with other molecules. Aroma depletion during fining is generally observed as a secondary, nonspecific effect of bentonite, but mechanisms and occurrence in white wines are not clear. The effect of fining on odor-active compounds of two white wines was examined using three samples of sodium bentonite applied at three different concentrations. Two Chardonnay wines were produced with different winemaking processes to obtain two wine styles. The period of aging on lees was adjusted to produce two different protein contents. Bentonite dose, bentonite sample, and wine style significantly affected the percent reduction of some odor-active white wine compounds during bentonite fining. Most of these volatiles were indirectly removed via deproteinization, as they can be fixed to macromolecules by weak bonds, and only a few odor-active molecules were directly removed by bentonite through adsorption. Moreover, low adsorbent amounts, useful to stabilize wine, did not significantly affect the concentration of the most odorous substances. Results suggested that the chemical nature, the hydrophobicity, initial concentration of wine odor-active compounds, and the abundance and nature of wine proteins are the “matrix factors” modulating the removal of wine odor-active compounds during bentonite fining.