Abstract: In order to study the malolactic fermentation (MLF) characteristics of Lactobacillus hilgardii Q19, isolated from the wine-producing area in the eastern foothill of Helan Mountain, at low temperature and its effect on the aroma components of wine, MLF was carried out in Cabernet?Sauvignon wine at 10, 15 or 20 ℃ after being inoculated with L. hilgardii Q19. Wine without MLF was set as the control. Bacterial growth, the consumption of L-malic acid and the aroma components in wine before and after MLF were tested and compared at different temperatures. The results showed that strain Q19 could start MLF and produce lactic acid at all temperatures. This strain had good fermentation ability at 15 and 20 ℃, and for the two temperatures, the concentration of malic acid in wines decreased to 0.27 and 0.15 g/L at 28 days after inoculation, respectively. However, the fermentation ability was weakened at 10 ℃, and the concentration of malic acid was 0.87 g/L at 28 days after inoculation. For each temperature, the bacterial density decreased during the first 8 days after inoculation and tended to be stable at 106–107 CFU/mL from day 24 onward. The contents of citric acid and total sugars decreased slightly at 28 days, while the content of total volatile acids increased but not significantly, with the smallest increase being observed at 15 ℃. The types and contents of aroma components produced during fermentation at 15 ℃ increased compared to those produced at 10 and 20 ℃. The increase in 1-octanol, ethyl heptanoate, ethyl nonanoate, ethyl lactate, undecanoic acid ethyl ester, decanal and terpenes (terpinene, β-pinene, inalol and citronellol) imparted unique floral and fruity aromas to wine, increasing the complexity of the aroma. L. hilgardii Q19 could complete MLF at 15 ℃ improving the aroma quality of wine, and thus it has good application potential in MLF in Northwest China with low temperature.

Key words: Lactobacillus hilgardii; low temperature; malolactic fermentation; aroma compounds