Malolactic fermentation (MLF) — consequence of skipping the conversion of malic acid to lactic acid If a winemaker elects not to carry out malolactic fermentation, which risk or outcome remains most concerning for wine stability and quality?

Introduction / Context:
Malolactic fermentation (MLF) is a secondary fermentation in which lactic acid bacteria decarboxylate malic acid to lactic acid and carbon dioxide. Besides softening acidity, controlled MLF stabilizes wine by reducing a substrate that could fuel spoilage in bottle.

Given Data / Assumptions:

• Primary alcoholic fermentation is complete.
• MLF has not been performed or inhibited/sterilized.
• Residual malic acid remains as a potential substrate for lactic acid bacteria.

Concept / Approach:

Without MLF or adequate stabilization (sterile filtration, SO2, low pH management), lactic acid bacteria may initiate spontaneous MLF in bottle, causing haze, off-flavors, carbonation, and packaging failures. MLF does not cause malic acid to precipitate as crystals (that issue pertains mainly to potassium bitartrate from tartaric acid).

Step-by-Step Solution:

Verification / Alternative check:

Winemaking SOPs recommend either completing MLF under control or preventing it via sterile filtration and adequate SO2—highlighting the stability rationale.

Why Other Options Are Wrong:

Crystals (option b) are from tartaric salts, not malic acid. Low acidity (option c) is the opposite—skipping MLF maintains higher, sharper acidity. Odd odor (option d) is not an inevitable immediate result. Alcohol drop (option e) is negligible during MLF and not “sharp.”

Common Pitfalls:

Confusing tartrate stability with MLF; both are separate stabilization practices. Also, believing MLF is always desirable—some crisp whites intentionally avoid MLF but then require sterile stabilization.

Final Answer:

The wine may be microbially unstable (spontaneous MLF later in bottle)