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.
The nature of undesirable and unfilterable haze particles observed by craft breweries remains nebulous and presents a challenge when the aim is the production of bright beer. A commercial beer was studied in which the brewery had sporadically encountered unfilterable haze. In this study, it was hypothesized that unfilterable haze particles were formed due to increased concentrations of proteins, polyphenols, and/or beta-glucans. Samples of a high haze and low haze India Pale Ale were degassed and digested with enzymes amyloglucosidase, pepsin, and UltraFlo Max (Novozymes TM ). Additionally, the protein, polyphenol, and beta-glucan content of each sample was measured. When comparing protein, polyphenol, and beta-glucan concentrations substantial differences between high haze and low haze protein concentrations were observed. Due to the unfilterable nature of these hazes, combined with experimental findings, it was hypothesized that yeast cell-wall proteins were responsible for this haze. Understanding of the source of these hazes offers brewers the opportunity to mitigate against their formation by adjusting brewing practices. Experimental SamplesThe control sample was a lager that had not been dry hopped, which had consistent low levels of turbidity < 1.0 EBC (European Brewing Convention) units and was produced in the same brewery as the experimental beers. The experimental beers used in the study were industrially
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