How does fermentation, filtration and stabilization of beer affect polyphenols with health benefits
Alexandr Mikyška | Martin Dušek | Martin Slabý
Phenolic substances affect the quality of beer and some of them have the health benefit for the consumer. Their content in the final product is influenced by a number of raw material-technological factors. We carried out 200 L pilot brews of pale lager with the different maturation period and similar brews focused on the effect of filter material (depth filtration plates /DFP/ and polyester sulfone membrane /PES/) and beer stabilization with protein and polyphenol sorbents. Flavonoids were determined using liquid chromatography in conjunction with high resolution mass spectrometry (LC-HR/ MS) and sample preparation by QuEChERS method. Additionally, total polyphenols and anthocyanogens was measured. The major reduction of both total polyphenols and flavonoids occurred in the first 2–3 weeks of maturation, the longer maturation had no impact on the loss of polyphenols. Filtration of beer with DFP significantly reduced the amount of anthocyanogens, but had no effect on monomeric flavonoid polyphenols. This technique could improve colloidal stability while preserving flavonoids. Conversely, PES membrane filtering greatly reduced the prenylflavonoid content (by 85%), and reduced the amount of flavanols and flavonols at levels comparable to those of PVPP-based polyphenol sorbent (25–35%). Flavonoids in beer could be largely influenced not only by PVPP treatment, but also by membrane filters used for both cold sterilization and primary beer filtration. Protein sorbent stabilization did not affect the content of flavonoids in beer. Decreases in flavonoid glycosides during filtration/stabilization were always lower than those of free flavonoids.
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