Unfiltered wines: what is the difference?

Putting the word “unfiltered” on a wine label instantly boosts the perception of superiority. Some wine consumers view the label “unfiltered” as a status symbol. It’s akin to photographers claiming that their Instagram pics are unfiltered. It gives a sense of authenticity and naturalness.

So why do we filter wine?

The whole point of filtration is not just to ensure that the wine is clear, but also to remove bacteria and yeast cells that may cause unwanted fermentations post-botteling. Wild yeasts or even Saccharomyces cerevisiae can cause off flavours to develop in the wine such as overt yeasty notes and vegetal notes. Brett yeast (Brettanomyces) can cause foul-smelling volatile phenols to develop in the wine, to the dismay of wine quality. These notes will, of course, develop over time and only if the wine contains microbial cells.

Does filtration affect the sensory profile of wine?

Studies have found that crossflow filtration method had some influence on red wine. The sensory panel perceived unfiltered red wines as less fruity and more earthy, oaky and smoky than filtered wine, especially after some bottle maturation. Another study on crossflow filtration showed that there were some minor differences in the flavour profiles of filtered and unfiltered wines, although no textural differences.

Pad filtration, on the other hand, had a limited effect on wine perception. A study done at the University of California, Davis have found a limited sensory effect between filtered and unfiltered red wines. The only attribute that differed significantly was a decrease in astringency in Merlot.

Another study touched on sterile filtration. Most winemakers are concerned that sterile filtration will strip their wines of colour, aroma and flavour. A study on white and red wine has shown some differences between the sensory profiles of white or red wine before and after sterile filtration, although limited. Like pad filtration, the most prominent difference was a decrease in astringency in red wine.

Overall, it appears as if filtration may have some effects on the sensory characteristics of wine and if so, the impact can be negative. The type of filtration affects to what extent wine perception will be impacted. But indeed, such effects are limited and subjective. All of this makes sense since the sensory molecules in wine are mostly larger than the 0.45-micron filter size that many (but not all) winemakers use to filter their wines.

Do not stop trying!

As always with new fashions, there is certain amount of unwarranted hype attached to unfiltered wines. Today, consumers are more aware of the benefits of natural, unprocessed foods and want to project such healthy features to wine. Whilst unfiltered wines undoubtedly undergo less processing and human intervention, for these very reasons are more difficult to get right. Unskilled wine makers can leave undesired particles in natural wine and spoil it. Moreover, as research shows, filtering itself does not necessarily remove the flavour and the texture from fine wines. Our recommendation is to explore filtered and unfiltered wines by ourselves, do not stop at the first sips…and keep enjoying the pleasures of wine discovery.

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