Winemaking: Cloudy with a Chance of Wine

Stabilizing wines for heat stability is something most winemakers consider, especially for white and rosé wines.  Why do we care and what exactly is heat stability or more accurately, instability?  Grapes naturally contain proteins that survive the fermentation process.  When those proteins are exposed to heat, they can denature and form a haze or precipitate in the bottle.  There is nothing wrong with the wine and it is perfectly safe to drink; it might just look a bit cloudy.  We are less concerned about heat stability in red wines because 1) you can’t visually see the protein haze as easily, and 2) tannins tend to bond to proteins, causing them to precipitate out of the wine prior to bottling.

slightly hazy bottle of Sauvignon blanc with light sediment on bottom of bottle.

So, what can we do make a wine heat stable?  There are a handful of ways a winemaker can go about heat stabilizing a wine, the most common is fining with bentonite.  Bentonite is a negatively charged clay that binds very easily with the positively charged proteins and forces them to precipitate out of solution.  We typically achieve this by simply adding bentonite to the fermentation.  We select the lowest dose we think will achieve stability because bentonite is great at fining other beneficial parts of the wine like flavors and aromatics.

What happened with our 2024 Sauvignon Blanc?  During the 2024 harvest, we fermented our white wines and rosé on the same low dose of bentonite that we have always used.  We chose not to do any extra fining post-fermentation to avoid removing the lovely aromatics and flavors that had developed during fermentation.  Unfortunately, this vintage of Sauvignon Blanc had a higher protein level than previous vintages, but we didn’t realize it until after the wine had been bottled.  What does this mean?  Your bottles of Sauvignon Blanc should look clear, however, if the bottles are exposed to heat (for example, left in a hot car), you might notice a slight haze or cloudy appearance in the wine.  There is nothing wrong with the wine, it is perfectly safe to drink.  Our decision to do the most minimal intervention possible during fermentation resulted in a wine that is unfortunately not heat stable.

In general, Sauvignon Blanc tends to have heat stability problems because it naturally contains a higher concentration of heat-sensitive proteins compared to other varietals.  As a winemaker, the tough decision is deciding how much to fine the juice/wine for aesthetic purposes vs avoiding over fining of aromatics and flavors.   We hope you enjoy our 2024 Sauvignon blanc, and if you end up with a slightly hazy bottle, appreciate all the challenges of winemaking and the knowledge you're supporting a small, boutique winery.