Unfilterable Beer Haze Part II: Identifying suspect cell wall proteins

Margaux Huismann, Fraser Gormley, Dzeti Dzait, Nik Willoughby, Kelly Stewart, Robert Alexander Speers, Dawn Louise Maskell

Research output: Contribution to journalArticlepeer-review

Abstract

The use of various diagnostic techniques has been previously utilized in the assessment of a commercially available India Pale Ale with cases of sporadically occurring unfilterable haze. The results from Part 1 suggested that β-glucans and proteins were the cause of the unfilterable haze and it was postulated that cell wall mannoproteins may also be a culprit of the unfilterable beer haze. In this follow-up study, proteins from high haze and low haze beer samples were precipitated and assessed using SDS-PAGE. Polyphenol interferences observed on the SDS-PAGE indicated that protein purification and targeted analysis was required. Proteins from high haze and low haze samples were fractionated and qualitatively identified via LC-MS. A library was built from FASTA sequences of targeted yeast proteins to qualitatively analyze the high haze and low haze samples. The protein fractionation was successful at purifying and isolating proteins from high and low haze samples. Two protein peaks were observed in the high haze sample, while one protein peak was observed in the low haze sample. The targeted LC/MS analysis discovered the presence of yeast cell wall mannoproteins and flocculation proteins, particularly Flo1 and Flo9. Understanding the source of these hazes can provide an opportunity for brewers to mitigate against their formation by adjusting brewing and yeast management practices.
Original languageEnglish
JournalJournal of the American Society of Brewing Chemists
Early online date12 Jul 2021
DOIs
Publication statusE-pub ahead of print - 12 Jul 2021

Keywords

  • Turbidity
  • Haze
  • Mannoproteins
  • Unfilterable
  • Proteins

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