UC Davis Researchers Unveil Faster Wine Clarification Method

Researchers at the University of California, Davis say they have developed a faster and more sustainable way to keep white and rosé wines clear, a step that could reduce waste, water use and product loss in a process that has changed little in more than a century.

The work, led by Ron Runnebaum, a professor of chemical engineering and viticulture and enology, and Ece Goktayoglu, a doctoral student in chemical engineering, focuses on removing the proteins that can make wine turn cloudy after it is shipped or stored. The haze does not make the wine unsafe to drink, but it can hurt sales because consumers often see it as a defect.

Their study, published in ACS Food Science & Technology, describes a flow-through system that uses a non-swelling ion-exchange resin to pull out haze-forming proteins from wine. Unlike bentonite, the clay now widely used in wineries, the resin can be cleaned and reused. The researchers say that could cut down on solid waste and reduce the amount of water needed for treatment.

White wines such as chardonnay, sauvignon blanc and pinot grigio are especially vulnerable to protein instability. Temperature changes during transport or storage can cause proteins to unfold and clump together, creating the cloudy appearance that wineries try to prevent before bottling. Runnebaum said the issue affects producers well beyond California and noted that about half of white and rosé wines worldwide require some kind of protein stability treatment.

Bentonite has long been the standard fix. Wineries mix the clay with water to form a slurry, add it to wine, then wait for the proteins to bind to the clay before removing the mixture through settling and filtration. But the process can take days, requires extra filtration and can lead to as much as 10% wine loss because of bentonite’s swelling properties. It also creates waste that must be handled after each use.

Goktayoglu said the goal was to find an alternative that would avoid losing wine and would be more sustainable. In the new system, wine passes through a column packed with resin. The proteins bind to the material as the treated wine flows out the other side. The researchers said the method worked across a range of conditions in model wine solutions designed to mimic white wine chemistry.

Because the resin does not swell like bentonite, the system could allow wineries to process wine continuously and potentially send it straight to bottling. Runnebaum said treatment time would likely be measured in minutes or hours rather than days. He said producers would also be able to treat only part of a large tank if needed instead of handling an entire batch at once.

The resin has a higher upfront cost than bentonite, but the researchers expect savings over time from lower labor needs, less product loss and reduced water use. Goktayoglu is now working on a techno-economic analysis to measure those factors more precisely. She is also studying how much protein must be removed before wine becomes stable, since the aim is not to strip out all proteins.

The UC Davis team said its approach could give wineries more flexibility at a time when producers are under pressure to cut waste and use fewer resources while still delivering wines that stay bright and clear from production through sale.