Comparison between Simultaneous and Traditional Consecutive Malolactic Fermentations in Wine
Successfully inducing malolactic fermentation in the production of grape wines can be challenging, especially in wines after finishing alcoholic fermentation with limited energy sources, low pH values and high ethanol concentrations. In this thesis, the kinetics of several chemicals of enological relevance were studied in a white wine (Chardonnay) and a red wine (Cab Franc) vinified by traditional, consecutive alcoholic (AF) and malolactic fermentations (MLF), and simultaneous AF/MLF, where bacteria were co-inoculated with yeast. The Chardonnay must was adjusted to four pH values (3.20, 3.35, 3.50 or 3.65), the cab Franc was kept as original pH value (3.56) and the concentrations of sugars, organic acids as well as acetaldehyde were followed throughout the fermentations. For Chardonnay the degradation of glucose and fructose was slower at the lowest must pH value (3.20) and independent from the time of bacterial inoculation. In all cases, malolactic conversion was faster after yeast-bacterial co-inoculation and was completed in simultaneous treatments at pH values of 3.35-3.65, and consecutive treatments at pH 3.50 and 3.65. No statistically significant difference was observed among the final acetic acid concentration, in all inoculation and pH treatments. For Cab Franc, it confirmed that co-inoculation shortened the fermentation periods while having minor effects on other parameters. Overall, simultaneous AF/MLF allowed for greatly reduced fermentation times, while the must pH remained a strong factor for fermentation success and determined the final concentration of various wine components. The time of inoculation influenced formation and degradation kinetics of organic acids and acetaldehyde significantly.