‘Unfiltered and unpasteurised’ if a phrase often used on the packaging of craft beers and sake. As the words suggest, this means the product has not undergone filtration, nor has it been subjected to heat pasteurisation. Consequently, microorganisms, particularly yeast, remain alive within it.
In sake terms, this corresponds to “nama-zake” (unpasteurised sake), which is akin to freshly pressed sake. It retains the sweetness of the rice and a fresh aroma, with a rich, robust flavour profile. Similarly, in beer, the “unpasteurised, unfiltered” production method allows the malt's umami, the delicate aromas and flavours of the hops, and the fruity, lively character derived from the yeast to be fully realised. So how detrimental is this filtration process to beer? We'd like to delve a little deeper into the advantages and disadvantages of filtration, and explore a modern alternative production method known as “centrifugation”.
For many brewers in the craft beer industry, attitudes towards “filtration” can be somewhat complex. This is because many brewers, who wish to preserve as much of the beer's aroma and flavour as possible, view filtration as something that robs the beer of these qualities. And this isn’t incorrect, although filtration hasn’t always been treated as the enemy in such a way.
In the early days of craft beer, filtration was common for most beer styles, including IPAs. The prevailing view at the time was that cloudiness in beer was often a defect, and indeed, it frequently was. However, as time passed, hop usage increased, IPA recipes evolved, and consumer preferences shifted. Cloudiness came to be welcomed as a unique characteristic.
Yet, when traditional filtration methods were applied unchanged to modern styles, many brewers began to feel that the filtered beer lost the very flavours they were desiring, making the beers cleaner but more muted. The reason was that the filtration media commonly used at the time worked by removing even the most minute particles. In essence, while highly advanced filtering technology produced beautifully clear beer, it also stripped away the very hop oils and flavour compounds that contribute to beer's appeal.
This is particularly true for IPAs: increased hop usage means higher levels of hop oils in the beer, which are the source of aroma and flavour. These hop oils not only cause cloudiness but also have a tendency to bind with yeast, proteins, and hop-derived particulates. Removing these solids during filtration, therefore, simultaneously strips away the hop oils and flavour compounds.
Consequently, it is understandable that some brewers believe ‘filtration ruins beer’.
However, there are are two sides to the story.
This ‘removal’ process is in many ways beneficial for beers like lagers and Kölsch, which demand a clean, crisp taste. While unfiltered versions of these styles exist, and they have their own benefits, filtration does indeed make these styles cleaner and crisper. Perhaps even more significantly, removing organic matter from beer is crucial for its shelf life. Residual organic matter decomposes over time, causing unpleasant odours and off-flavours. The quantity and types of organic matter in beer vary by style, significantly influencing its best-before date and storage stability. In countries where lagers are a mainstay of the beer culture, like Germany and the Czech Republic, refrigerated distribution is rare, and the choice is therefore a very high turnover or increased shelf stability.
So, how can we remove unwanted organic matter while retaining the aroma and flavour compounds without filtration? Enter the centrifuge!
Centrifuges themselves are devices long used by major brewers, employed to preliminarily clarify beer before final filtration. The mechanism involves spinning a conical disc at high speed within a container, flinging heavier solids to the periphery to separate them from the liquid.
Modern brewers, especially with the growth of craft beer, have learned to finely control the degree of centrifugation to determine how much solid matter is removed from the beer. In other words, the same equipment can be used to produce everything from sparkling, crystal-clear lagers to hazy IPAs with a touch of cloudiness, and even Hefeweizens that retain their yeast.
It is no exaggeration to say that this centrifuge is one of the most important investments for a growing brewery. By efficiently processing the hop and yeast residues that accumulate at the bottom of the tank, it not only reduces losses during production, but also increases the stability of the beer by reducing organic matter, enabling it to maintain its quality over a long period of time. And, of course, it does all this while maximising the aroma and flavour of the beer, which is something that filtration alone could not achieve.
Kyoto Brewing Company introduced this centrifuge last year. This coincided almost exactly with the start of our new KBC 2.0 initiative, where we began brewing many hop-forward beers. Using this centrifuge allows us to control the condition of a wide variety of beer styles more precisely and maintain the intended flavour profile for longer.
Fun fact: I (James) was fortunate enough to be on the front line in the early adoption of centrifuges into craft beer, and making hazy beers with a centrifuge was a foreign idea even to the centrifuge manufacturers themselves. I was often told “you can do that it will make the beer hazy” in which case I replied, “I know that is the point!” which was greeted by a funny slightly disapproving look in return as they thought I was crazy. Since then, these manufacturers have made modifications to centrifuges in be able to better handle high hop loads and are marketed in craft brewers making hazy IPA’s!
