Sparkling Wine filtration

Hello new and faithful readers!

Welcome to the second installment of my now very delayed second (not yet monthly) newsletter. This month we’re looking at the impact filtration has on foam.

Filtration is a common practice for most commercially produced white/rosé wine to create a brilliantly clear product. There are two main reasons a winemaker will filter: clarity and microbial stability. A third reason to filter, unique to sparkling production, is colloids and particles. These can either have a positive (stabilization) effect, or negative (destabilization) effect on foam in sparkling wine.

A quick overview on foam stability: Foam is always working against gravity. In order for foam to resist gravity for as long as possible there needs to be some kind of matrix holding the bubbles together. Foam stability is influenced by three major components: viscosity, beneficial particles, and destructive particles. Foam stability is increased when viscosity is increased. Viscosity is influenced by temperature, colloids, and alcohol. Beneficial particles including proteins have electrical charges that push and pull each other creating a film in which bubbles can resist gravity for a longer time. Destructive particles (surfactants) can break apart the desirable film by spreading over the surface, causing the foam to collapse quickly. Having fewer of these destructive surface active components yields longer lasting foam.

Filtration is a VERY delicate process in sparkling production because of it’s effect on foam. The purpose of the filter is to remove many of these beneficial particles. Some producers choose to not filter their base wine to maximize the amount of particles and colloids in their wine. Some producers choose to lightly filter their wine to around 1 micron to clarify their wine and preserve some of the components for foam friendly matrices in the base wine. Lastly some producers will sterile filter the wine (0.45 micron or less), sacrificing some foam longevity for microbial stability.

Research has found that particles and colloids positively impact the longevity of foam and removing these reduces this benefit. With the exception of large particles (>3 micron). It has been found that large particles in base wines negatively impact foam stability due to their foam destructive characteristics.

Before you come to the conclusion that you’ll stop filtering your base wine to improve your foam. Keep in mind, there can be too much of a good thing. Large particles in your wine can become nucleation sites for carbon dioxide causing CO2 to rapidly leave the wine when there is a sudden change in pressure. This is affectionately known as gushing. Anyone who has opened a high pressure, cloudy pet nat, is familiar with this concept. Gushing can be problematic for both the disgorging crew and the consumer.

The research that I’ve read seems to acknowledge filtration for sparkling is incredibly impactful yet not entirely understood acedemically. Wine is a complex matrix and there are many variables impacting foam quality, including/especially filtration.

Resources used:

^{Kemp, Belinda, et al. “Chemical Compounds and Mechanisms Involved in the Formation and Stabilization of Foam in Sparkling Wines.” Critical Reviews in Food Science and Nutrition, vol. 59, no. 13, 7 Mar. 2018, pp. 2072–2094, https://doi.org/10.1080/10408398.2018.1437535.}

^{L. Viaux, et al. “The Impact of Base Wine Filtration on Champagne Foam Behavior.” American Journal of Enology and Viticulture, vol. 45, no. 4, 1 Jan. 1994, pp. 407–409, https://doi.org/10.5344/ajev.1994.45.4.407. Accessed 29 Dec. 2023.}

^{Marchal, Richard, and Philippe Jeandet. Macromolecules and Champagne Wine Foaming Properties : A Review. 2007.}