Wine Thermosensitive Proteins Adsorb First and Better on Bentonite during Fining: Practical Implications and Proposition of Alternative Heat Tests

Abstract : Bentonite fining is the most popular treatment used to remove proteins in white and rose wines. The usual heat test used to adjust the bentonite dose consists of heating the wine during 30 min at 80 degrees C. At this temperature, all of the proteins are unfolded, and this can lead to an overestimation of the dose. We have shown that proteins adsorb on bentonite in a specific order and, more importantly, that the proteins responsible for haze formation adsorb first. Fluorescence spectroscopy showed that this is due to the structural properties of proteins, which can be classified as hard and soft proteins. Alternative heat tests were performed at a lower temperature (40 degrees C) and showed a better correlation with accelerated aging. These tests were also less dependent upon the wine pH.