Changes

There are two types of pasteurization methods used in brewing: tunnel pasteurization and flash pasteurization. In tunnel pasteurization, which is more widely used in breweries, cans or bottles of packaged beer is moved slowly through a tunnel of fixed temperatures. In flash pasteurization (or plate pasteurization), large quantities of beer is are pasteurized at the same time via a heat exchanger and is often used to usually performed before the beer is packaged <ref name="Vaughan_2005" />. Since thermal death rates for beer spoilage organisms has been identified to be under 140°F (60°C) for 15 minutes <ref>[https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1946.tb01593.x THERMAL DEATH POINTS OF MICRO-ORGANISMS IN BEER. Aage Lund. 1947.]</ref>, this is the baseline temperature and time for pasteurization, although higher temperatures and shorter times are used for some pasteurization methods (see the below links).  Microfiltration is an alternative technology to heat pasteurization that can be used to pasteurize beer. Microfiltration uses a set of membranes, usually in the 0.45–0.65 μm range, for filtering bacteria and yeast. Bacteria have a cell size of about 5-10 μm and yeast species have a cell size of about 5–16 μm, while flavor compounds such as phenols are filtered out when using a smaller diameter filter such as 0.2 μm. One study by Bernardi et al. (2019) found that filtration with polyethermide membranes removed around 1-2 IBU, ~30% of yeast-produced phenolic compounds (most polyphenols from hops were not filtered out), and larger tannins (which were only a small portion of the total polyphenol content). The antioxidant activity was largely not impacted. After filtration, the beers were 26%-33% lighter in color, depending on the style of the beer, and were 100% clearer. The filtration that was used, which was 1.2 μm, also produced fully pasteurized beers <ref>[https://www.sciencedirect.com/science/article/pii/B9780128152584000135 Microfiltration for Filtration and Pasteurization of Beers. Guilherme dos Santos Bernardi, Jacir Dal Magro, Marcio A. Mazutti, J. Vladimir Oliveira, Marco Di Luccio, Giovani Leone Zabot, Marcus V. Tres. 2019. DOI: https://doi.org/10.1016/B978-0-12-815258-4.00013-5.]</ref>.