Malolactic fermentation (MLF) in wine: outcomes and sensory impact Which of the following correctly summarizes key results of malolactic fermentation in winemaking?

Introduction / Context:
Malolactic fermentation (MLF) is a secondary fermentation carried out mainly by Oenococcus oeni and related lactic acid bacteria. It is widely used in red wines and some whites (e.g., Chardonnay) to modify acidity, microbial stability, and flavor.

Given Data / Assumptions:

• MLF occurs after or near the end of alcoholic fermentation.
• Malic acid is converted to lactic acid and CO₂.
• Some metabolic by-products affect aroma (e.g., diacetyl).

Concept / Approach:
Biochemically, MLF decarboxylates malate to lactate, which has a softer taste. This conversion typically lowers titratable acidity and raises pH slightly. Flavor compounds like diacetyl may emerge, contributing buttery aromas in certain styles if not metabolized further by yeast or bacteria.

Step-by-Step Solution:

Verification / Alternative check:
Cellar monitoring tracks malate depletion by enzymatic assays or paper chromatography; sensory and analysis confirm reduced TA and presence/absence of diacetyl depending on management.

Why Other Options Are Wrong:

• Single components (a, b, or c) are each true but incomplete; all occur in MLF.
• “Increases malic acid concentration” is opposite to the defining reaction of MLF.

Common Pitfalls:
Assuming diacetyl is inevitable; it depends on timing, racking, and residual yeast metabolism. Also, MLF can compromise freshness in delicate aromatics if not intended.

Final Answer:
All of these