Photo by: Denise M. Gardner
Better wine doesn’t always require better grapes. Sometimes it just requires a better process.
For many wineries across the U.S., pre-bottling operations are exactly where quality is won or lost, and small adjustments to this stage can make a significant difference in what ends up in the bottle.
Pre-bottling steps typically include:
- Final blending and sensory evaluation
- Cold stabilization
- Heat (protein) stabilization
- Preservative additions
- Filtration
These steps may seem straightforward, but the order and timing in which they’re executed matters more than most winemakers realize. Here are three habits worth adopting to make your pre-bottling process smoother, more consistent, and less stressful on bottling day.
Cold Stabilization: The First Step that Sets the Stage
For wines that require cold stabilization (i.e., whites, rosés, sweet wines, and many native or hybrid varieties), it’s worth deciding on a cold stabilization method before moving forward with any additional stabilization processes. Cold stabilization directly affects a wine’s pH, and that final pH value has far-reaching implications: it influences protein (heat) stability, the efficacy of sulfur dioxide, and even the wine’s overall flavor profile. Getting the sequence right sets a more reliable foundation for every stabilization step that follows.
Photo by: Denise M. Gardner
Traditional cold stabilization methods, whether natural cold stabilization or contact seeding, have a direct influence on a wine’s pH. Wines entering the process at or below a pH of 3.60 will see their pH decrease, while those above 3.60 will experience a continued rise. Because of this, winemakers using traditional cold stabilization techniques are encouraged to complete cold stabilization before moving onto protein stabilization. Doing so ensures the wine’s pH has reached its final value, allowing for a more accurate and reliable protein stability assessment. (Author’s note: the pH 3.60 is a rough approximation. It is not the pure pH cut-off for pH changes due to cold stabilization practices. However, it is around this pH where winemakers can start to see increases in pH due to cold stabilization processes, and sometimes that is unexpected.)
When tank chilling capacity is limited, traditional cold stabilization may not be feasible. Beyond infrastructure constraints, some winemakers may deliberately choose to avoid traditional methods, whether to protect a wine with a naturally higher pH, or to preserve a pH and titratable acidity (TA) balance that is already exactly where they want it. In any of these situations, a tartrate inhibitor is typically the go-to solution for achieving cold stabilization without compromising the wine’s quality.
Tartrate inhibitors used for cold stabilization, many of which are gum-based, can interfere with a wine’s colloidal chemistry. This disruption is often perceived as a haze, which is similar in appearance to a protein haze. As a result, the addition of a tartrate inhibitor may alter the wine’s protein stability properties, making it essential for winemakers to account for this effect through thorough bentonite fining trials. Currently, the most reliable way to determine the wine’s bentonite needs, accounting for both the protein and colloidal balance, is to run fining trials without and with the tartrate inhibitor addition in the wine samples. DG Winemaking Clients and Members can find the full testing protocol outlined in the Bentonite Fining & Colloidal Stability Trials Protocol.
The choice of cold stabilization technique has a direct bearing on the order of subsequent stabilization processes. With traditional cold stabilization, cold stability is completed first, followed by bentonite fining for heat stabilization. When a tartrate inhibitor is used, however, the sequence flips: bentonite fining for protein stability is typically completed before the tartrate inhibitor is introduced to the wine.
DG Winemaking Clients and Members can reference the newly released Decision Tree: Cold Stabilization Processing Decisions to verify the recommended processing order for stabilization based on their cold stabilization approach.
Let Protein Stabilization Set Your Bottling Timeline
Many winemakers reach for bentonite shortly after primary fermentation to improve wine clarity, but holding off until pre-bottling operations is almost always the better choice for wine quality. Here’s why timing matters.
Protein stability is not a static property in the wine. Bentonite fining manages protein stability, but protein stability is directly tied to a wine’s pH, and pH doesn’t stay fixed throughout the winemaking process. Blending, sweetness adjustments, and certain cold stabilization techniques can all shift a wine’s pH. Bentonite fining before these steps are complete means winemakers may be solving a problem that’s about to change. Waiting until all alterations are finalized ensures the winemaker is working with an accurate picture of what the wine actually needs.
Additionally, effective protein stabilization requires wine temperatures of 55°F or above. Yet coming out of fermentation, most wines are chilled to their ideal storage range of 45–50°F, which is just cold enough to compromise the fining process and the wine’s dissolved carbon dioxide and oxygen levels. By waiting until pre-bottling, when wines can be brought back up to the appropriate temperature without having to get adjusted back down, bentonite can do its job properly without sacrificing the quality benefits of cooler wine storage.
Finally, defaulting to a “standard” bentonite concentration is a missed opportunity. Bentonite needs vary considerably from wine-to-wine and vintage-to-vintage. A given variety might require as little as 2 lbs./1,000 gal one year and up to 16 lbs./1,000 gal (or more!) the next. Factors like switching the bentonite product can shift requirements further still. Running bentonite fining trials before treatment allows winemakers to dial in the right dosage for each individual wine, protecting both quality and efficiency in the processing step.
DGW Clients and Members can reference the Bentonite Fining and Colloid Stability Trials Protocol to determine accurate dosage rates for any wine.
Streamlining Filtration: Processing Order Makes All the Difference
Filtration is one of the more technically demanding steps in winemaking and even experienced winemakers can find it confusing. But much of the difficulty can be reduced by following a deliberate processing order. Here’s what that looks like in practice.
Photo by: Denise M. Gardner
One thing winemakers can easily do to improve filtration operations, is stop spreading filtration processes out across several weeks. While this practice usually has good intentions to improve time management or enhance wine clarity along the way, it can also cause more work or become detrimental to wine quality. The problem is that filtration isn’t a “complete and check” process. As we discussed in Avoid Filtration Frenzy, each filtration pass does two things: it removes particulates above a certain size, and it molecularly disrupts the wine to prepare it for sterile filtration. That disruption isn’t permanent. The wine does come back together, as anyone who has dealt with bottle shock knows firsthand. Spreading filtration out over time doesn’t compound the benefits; it just adds unnecessary handling.
Barring major winemaking issues, filtration should be the last processing step before bottling — full stop. DGW recommends breaking it into a focused two-day sequence:
- Day 1 (pre-bottling day): Pre-filtration steps (i.e., plate-and-frame, lenticular, or cross-flow filtration).
- Day 2 (bottling day): Sterile filtration immediately before bottling.
If your operation is filtering outside of this window, it’s worth asking why. You may be spending extra time and effort on steps that aren’t moving the wine forward and potentially creating more problems than you’re solving.
Another common source of filtration errors is the timing of final wine additions. Sweeteners, filtration enzymes, finishing tannins, and preservatives like sulfur dioxide and potassium sorbate should all be added at a defined point prior to filtration and given adequate time to stabilize before filtration begins. A wine that was sweetened the day before filtration is not ready to filter. Building a consistent timeline for these additions removes a major variable from your pre-bottling process and reduces the risk of unexpected filtration problems such as clogging.
For a complete guide to standardizing your pre-bottling operations, refer to the DGW Checklists / Timelines for Pre-Bottling Operations:
The views and opinions expressed through dgwinemaking.com are intended for general informational purposes only. Denise Gardner Winemaking does not assume any responsibility or liability for those winery, cidery, or alcohol-producing operations that choose to use any of the information seen here or within dgwinemaking.com.
