SMALL CRAFT ADVISORY: Shaping Craft Brews with Filters

While overall U.S. beer sales have dropped 1% in 2018, craft brewer sales grew by 4%, reaching 13.2% of the total market. As well, retail sales of craft brews increased 7% up to $27.6 billion, accounting for more than 24% of the $114.2 billion U.S. beer market. And recently, 134 brewers, brewery owners and employees climbed the steps of Capitol Hill in support for the recently expired Craft Beverage Modernization and Tax Reform Act, which lowered federal excise taxes on breweries, wineries, and distilled spirits producers for a period of two years. Brewers said the saved money was reinvested in their businesses, undoubtedly accounting for a large portion of the craft beer industry growth. More growth is likely, as the legislation currently has the support of 160+ members in the House and more than half in the Senate. 

With over 7,000 small and independent breweries in the United States—about half of which are brewpubs with the other half microbreweries serving local or regional markets—opinion concerning proper beer filtering no longer battles it out in myth, but in the marketplace. Most of these debates are over one, evergreen brewing point which some may argue is the only point worth debating: flavor. Traditional thinking splits on filtering and its affect on many elements of brewing — from safety and clarity to carbonation and aging. But in terms of filtering removing flavor in favor of longer shelf life and heavily reduced yeasty finishes, myth has given way to style. 

Beers are filtered to three basic levels—rough, fine and sterile—and involve a number of steps. The first is clarification following the fermentation process, when yeast is used to convert sugars from grain to alcohol. Generally this is accomplished utilizing a plate and frame filter with a pad or cloth along with a pre-coat of diatomaceous earth (DE). An alternative to this step is lenticular technology such as the Graver GSTACK. The cellulosic filter provides for outstanding dirt loading necessary at this stage as well as the absorptive characteristics of DE. When a filter press is utilized, the risk of DE unloading or bypassing exists, therefore a 5 micron trap filter is used as precaution. This filter can vary from a nominal melt blown to a high-efficiency pleated. As such, opportunity exists for Stratum C, QXL or PMA, depending upon price point desired, as well as quality of the plate and frame equipment. 

Removing yeast, however, alters the balance of the beer and affects a secondary fermentation process that adds carbonation, albeit at much reduced concentrations. When artificially carbonated—as in the case with commercial brewers and kegging—the residual yeast is less important yet always informs flavor. Yeast adds a smooth body to beer which is considered desirable in most ales. However, too much yeast can mask hoppiness, aroma and maltiness, and remove proteins that give beer its "head". Some brewers remove the filtering process altogether to produce a more artisanal taste, but their product is not for bottling and is most often sold at the place of production. For most cases, the rule is simple: err on the side of less yeast, but select your filtering to produce the specific style of beer you want.

Beer process filtering is also essential in terms of microbial stabilization prior to bottling. While most regional and large breweries utilize flash pasteurization in the bottling process, these processes are typically too costly for a craft brewer. Instead, they use membrane filters that have bioburden reduction claims along with a suitable prefilter. The typical recommendation would be the 0.45 micron ZTEC WB which has specific claims for spoilage organisms. Multi-layered prefilters such as the 1 micron QMC offer ideal protection to the membrane filters, although depending upon the nature of the beer, the PMC or PMA are viable options. 

Other essential filtration involves the water used in the process, keg and bottle washing, system sanitization (in particular, in the case of filter reuse) and equipment rinsing. As in most processes, the end product—whether it be an ale, lager or pilsner—is only as good as the ingredients that go into it.