Chaptalization in winemaking — What practice does this term specifically refer to when adjusting a must before or during fermentation?

Introduction / Context:
Chaptalization is a legally regulated adjustment used primarily in cooler regions where grapes may ripen with insufficient sugar. The goal is to increase potential alcohol without materially changing flavor by adding sucrose to the fermenting juice (must).

Given Data / Assumptions:

• Must sugar concentration influences final alcohol by volume.
• Laws differ by region; the technique is not permitted in some appellations.
• Chaptalization is distinct from back-sweetening or dosage.

Concept / Approach:
Added sucrose hydrolyzes to glucose and fructose, thereby boosting fermentable sugar pool. This raises ethanol yield after complete fermentation while keeping residual sugar unchanged if fermented to dryness. It is not intended for sweetness adjustment in finished wine.

Step-by-Step Solution:

Verification / Alternative check:
Regional regulations and oenology texts define chaptalization specifically as must enrichment with sugar prior to or during fermentation.

Why Other Options Are Wrong:

• b/d: Grape juice additions adjust composition but are not chaptalization.
• c: Dosage in sparkling production sweetens finished wine, not must; different purpose.
• e: Water addition is dilution, not chaptalization.

Common Pitfalls:
Confusing chaptalization with back-sweetening; they occur at different stages and have different objectives.

Final Answer:
Adding sucrose to must to raise potential alcohol