How can malolactic fermentation be prevented?

• A. Temperature below 15C
• B. Moderate SO2
• C. Filtration
• D. Low pH

Answer: (A)

Malolactic fermentation is driven by lactic acid bacteria that convert malic acid into lactic acid, softening the wine. These bacteria are highly temperature dependent. Keeping the wine cold, around or below 15°C, slows their metabolism so much that malolactic conversion hardly occurs, effectively preventing the process from starting or progressing. Other factors can influence suppression—sulfur dioxide can inhibit bacteria to some extent, filtration can remove them if done before Malo begins, and lower pH makes the environment less favorable—but these are less reliable or practical than simply chilling the wine. So, the most consistent way to prevent malolactic fermentation is to maintain a cool temperature.