La Crescent is a cold-hardy hybrid white wine grape bred for cold tolerance and disease resistance. As with many other North American hybrid cultivars, its high concentration of proteins leads to unwanted haze in wine. There is anecdotal evidence based on winemakers’ observations, and limited experimental support, for improved protein stability in wines with oak contact. However, previous work has focused on Vitis vinifera varieties, which typically have significantly lower protein concentrations than hybrid cultivars. The goal of this work is to reduce the need for high rates of bentonite treatment in cold-hardy hybrid white wine varieties using commonly available, traditional winemaking techniques.
Trial results indicate that barrel fermentation is a promising strategy for cold-climate winemakers to reduce protein haze in cold-hardy hybrid white wines. In year 1, fermentation of La Crescent in a used oak barrel reduced turbidity from heat-sensitive protein haze by 56% compared to La Crescent fermented in a glass carboy. In year 2, fermentation of La Crescent in a used oak barrel reduced turbidity from heat-sensitive protein haze by 18% compared to La Crescent fermented in a steel tank.
While the amount of protein haze was reduced in the barrel-fermented wines, those wines still showed some protein instability when subjected to a heat test. In order to achieve full protein stability, treatment with bentonite would likely still be needed. However, the amount of bentonite required would be significantly reduced, and the contact time required would likely be cut down as well. By bringing the protein concentration into a lower range, better predictive additions of bentonite could be made, and there would be a lower risk of significantly over- or under-adding bentonite.
Using previously-used, “neutral” oak allows winemakers to continue producing La Crescent in a fresh, fruit-forward, aromatic style. Furthermore, by leaving the wine in contact with the barrel only for the length of the fermentation, winemakers can maintain the same quick-release timeline typical for that style of white wine when fermented in steel, while also minimizing the need for bentonite treatment. Using a neutral barrel would allow wineries to avoid purchasing new barrels for this purpose, the barrel would be freed up for re-use with other wines after the approximately two-week fermentation, and it could be re-used repeatedly with no additional cost and no risk of over-treatment. An important consideration is that storing and caring for used barrels requires labor and space, even if it does not require any new purchase.
The relative protein contents of other cold-climate white grape varieties are not well-studied, so future work should investigate the usefulness of barrel fermentation for protein stability in other North American hybrid white grape cultivars.