What is malolactic fermentation?

• A. A process of clarifying wine with fining agents.
• B. Primary fermentation converting sugar to ethanol.
• C. Secondary fermentation in which malic acid is converted to softer, lactic acid.
• D. A method of aging wine in oak.

Answer: (C)

Malolactic fermentation is a secondary fermentation carried out by lactic acid bacteria. After the primary fermentation finishes, these microbes transform malic acid, which is sharp and tart, into lactic acid, which is softer, plus they release carbon dioxide. This change lowers the wine’s perceived acidity and can add creamy or buttery notes through compounds like diacetyl. It’s not about clarifying wine with fining agents, not the primary fermentation where sugar becomes ethanol, and not oak aging. The description of a secondary fermentation in which malic acid is converted to softer, lactic acid matches what actually happens in malolactic fermentation, making it the best answer.