Alcoholic Fermentation Finished: Why a Winery Lot May Still Be Biologically in Process

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

The phrase fermentation finished can mean different things in a winery. Yeast converting grape sugar into alcohol is one process. Malolactic fermentation, usually called MLF, is another. When a buyer is considering wine inventory in a Sonoma winery acquisition, the distinction helps explain why a lot can have completed alcoholic fermentation while still requiring biological development and further cellar work.

This is more than terminology. It affects the production stage represented by the inventory and the use of winery production facilities during the period before packaging.

MLF changes an acid rather than repeating the first fermentation

The University of Minnesota’s 2016 explanation describes MLF as a bacterial conversion of malic acid into lactic acid. It distinguishes that process from primary yeast fermentation and describes analytical ways of assessing the remaining malic acid. The publication supplies a scientific explanation; its older kit prices are not used here.

Calling it secondary fermentation can obscure the difference if the reader imagines a second identical conversion of sugar into alcohol. The biological agent and the principal transformation differ. A statement that sugar fermentation is complete does not, by itself, establish the status of the malic-acid conversion.

Timing can overlap or follow

The AWRI’s August 2020 MLF fact sheet explains that the process can be managed at different times relative to alcoholic fermentation. It also discusses effects on acidity, stability and sensory development. Its description includes both sequential and overlapping approaches rather than a single mandatory production sequence.

That matters when interpreting a cellar calendar. Two lots harvested on the same day may follow different intended sequences. The elapsed time since harvest cannot independently establish that each lot has reached the same biological stage. A buyer needs to understand the process chosen for the product rather than assuming age alone determines readiness.

Wine style is part of the decision

MLF is not simply an instruction to make every wine taste buttery. The AWRI fact sheet describes several sensory influences and the role of different conditions and bacterial strains. The final perception belongs to the whole wine, not a single process label.

For an estate with several products, that creates a useful distinction between a lot intentionally undergoing conversion and a lot made under a different style objective. A product plan should explain the intended outcome. The presence or absence of one process is not a universal quality ranking across the portfolio.

Production stage affects the ownership calculation

Consider a hypothetical purchase including 10,000 liters described as finished with alcoholic fermentation. If additional biological processing, stabilization, blending and packaging remain, those liters are not equivalent to 10,000 liters of packaged wine ready for immediate sale. The difference concerns remaining work and time, not merely the wording of an inventory list.

A forecast that starts sales immediately after closing could therefore misstate cash timing. A more accurate model connects the actual lot status with the next production steps. It also recognizes that a vessel occupied by an in-process lot cannot simultaneously serve another planned use unless the operating sequence accommodates it.

Clear terminology makes the asset easier to understand

The useful acquisition narrative states which process is complete, which is intended and what evidence describes the lot’s current status. That gives the buyer a coherent picture of the wine and facilities being acquired. It avoids treating one broad word as proof that all remaining production costs have already been incurred.

Explore real estate and home for sale in Sonoma for the wider ownership setting. Contact Diamond Group Estates to discuss production-stage information in a winery acquisition.

Sources reviewed October 28, 2026: University of Minnesota’s October 2016 MLF explanation and AWRI’s August 2020 fact sheet. The inventory example is hypothetical; no inoculation, temperature, additive or completion threshold is prescribed.