(2 minute read)
The alcohol, low oxygen content, relatively low pH, hops extracts (alpha-acids) and dissolved carbon dioxide in beer inhibit the growth of pathogenic bacteria. That is why beer has been a safe drinking alternative for so many centuries. However, some microorganisms can survive and even thrive in beer and spoil the flavor and aroma of any good brew.
Beer can be spoiled by bacteria or wild yeasts. The most mentioned spoilage bacteria in beer are Lactobacilli and Pediococci.
Other possible spoilage bacteria are Pectinatus and Megasphaera species.
If wild yeasts such as Saccharomyces cerevisiae or Candida pelliculosa find their way into the brewing process they can cause off flavors and higher attenuation.
Lactic acid bacteria (LAB) and other organisms can provide some benefits to the brewer during the process, but they can cause spoilage issues if they remain in the beer after packaging.
The figure below shows a simplified beer clarification, stabilization, and packaging process. The fermentation and aging processes are complete in this example, and the beer has been bulk-filtered and stored in a bright beer tank.
The most critical filter in the figure is the Final Stabilization Filter (housing 4) – the one that removes the microorganisms discussed above. The most commonly used filter is membrane-based with either a 0.65 or 0.45-micron pore size.
Brewers may choose the smaller pore size to ensure the capture of all bacteria, including the vegetative forms of some species that may survive in the beer. But there is a risk that some flavor or color elements of the brew will also be captured by membranes with 0.45-micron pores. For that reason, 0.65-micron membranes may be used for darker or heavier beers. Brewers should test filters in their beer before choosing a micron rating or material to be sure that the filters will remove the target organisms and also preserve beer flavor and color.
Learn more by reading Protecting the Quality of Beer – Filters That Remove Spoilage Organisms.
To explore filtration solutions for brewing beer, visit Process Filter Products on our website.
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