Amanda Fleming and Renee Threlfall*
*University of Arkansas, 2650 N. Young Ave, Fayetteville, AR, 72704 (rthrelf@uark.edu)

Like many cultivars in the United States, Chambourcin (Vitis hybrid) grapes from warmer growing regions can have high pH at harvest, thus affecting wine quality. Acid additions or malolactic fermentation (MLF) can modify wine pH; however, non-Saccharomyces yeast, such as Lachancea thermotolerans, can modify pH, acidity, and other attributes during wine production. In 2021, 168 kg of Chambourcin grapes grown commercially in Arkansas were harvested and transported to the University of Arkansas System Food Science Department for wine production. The grapes were randomized into batches, crushed, and destemmed. Four inoculation treatments in duplicate were conducted using Saccharomyces cerevisiae (SC) with and without malolactic cofermentation (SC-MLF) and L. thermotolerans in a sequential inoculation with S. cerevisiae (LT-SC) with and without malolactic cofermentation (LTSC-MLF). Basic composition, sugars, and organic acids were evaluated daily during fermentation for 14 days at 21°C, with all inoculation treatments completing fermentation in six days (total sugars <0.3%). Prior to inoculation, soluble solids, pH, and titratable acidity (TA) were 18.78%, 3.51, and 0.73%, respectively, with the main acids as tartaric (0.31%) and malic (0.44%). Regardless of MLF, by fermentation day six, TA, lactic acid, and total organic acids were higher in LT-SC wines than in SC wines, while the pH of LT-SC wines was lower than SC wines. From fermentation day 0 to bottling, use of L. thermotolerans in Chambourcin wine production resulted in changes in acidity attributes, with reduced pH (~4%) and malic acid (~10%) but increased TA (~55%), lactic acid (64%), and total organic acids (~58%), regardless of MLF. Mixed fermentations with L. thermotolerans and Saccharomyces yeasts produced wines with lower pH and higher acidity, contributing to microbial and color stability while providing winemakers with options for producing more complex wines.

Funding Support: Lallemand, Inc