Treating wine with cation exchange (CE) resin is an accepted method to reduce pH and decrease tartrate instability. However, it has been shown that a side effect of this process seems to be an inconsistent shift of volatile and organic compound concentrations in the final product. CE can be especially useful when the pH and titratable acidity (TA) are both high, as other methods for pH reduction will exacerbate the TA issue. CE treatments at various concentrations ranging from 0 to 333 g/l were applied to three different types of wine and to a model wine with a single volatile of interest in order to characterize and model the change in volatile concentration. Two primary effects on the volatiles present in wine were observed, a reduction of overall volatile concentration correlated with the quantity of resin used, and a reaction in which some volatiles change into others in the presence of the CE resin at low pH. Three distinct concentration responses to treatment emerged, a strict linear decrease, an initial increase followed by a decrease, or no observable change in concentration, depending on the compound in question. Ethanol decreased from control to the highest treatment level by 1.8% ABV in a local pinot grigio, and again by 0.75% ABV in a model solution. It demonstrated a linear decrease, which lead to the hypothesis that the resin may be acting to store certain volatiles. Treated wines were then separated and analyzed by GC-MS to determine what aroma volatiles may be affected by CE treatments and to what degree. In a local Norton, 1-Hexanol concentration decreased from 1292 parts per billion (ppb) to 570 ppb. This was repeated in isolation in a model solution and in triplicate, and a strict linear decrease was again observed, an initial 400 ppb sample fell to 137 ppb, or 34% of its original value at the 333g/l treatment level. Another important volatile, and known stable end product of multiple breakdown reactions, 1,1,6,-trimethyl-1,2-dihydronapthalene (TDN) was observed in a local Syrah from starting at 1.8 ppb and increasing to around 14 ppb at the first treatment level, before decreasing to around 8 ppb at the 333 g/l treatment. This is of note because it takes TDN from below sensory threshold to above as an effect of the CE treatment. This research aims to further characterize and develop models to predict concentration changes in wine for the purpose of employing CE treatments in commercial wine production.

Model development for aroma changes in wine following cation exchange treatments

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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