Development of a method for assessing haze-active protein in beer by dye binding

Fifteen candidate dyes were combined with the haze-active (HA) protein glia din in a search for one that would produce a chromatic shift and form the b asis of an analytical method for HA protein in beer. Two dyes, alizarin red S and nuclear fast red, produced shifts in the UV region, and two, bromopy rogallol red (BPR) and plasmocorinth B, produced shifts in the visible rang e. The responses of these four dyes to proteins with a range of haze-formin g activity were compared. BPR was selected for method development. A statis tical experiment design and response surface modeling were used to determin e optimum conditions. BPR produced a linear response to gliadin in buffer, but it suffered interference in the beer matrix. Pretreatment of beer with a C18 cartridge and centrifugal ultrafiltration removed the interference. M easurements of HA protein via the BPR method and by haze induction with tan nic acid were performed on unchillproofed beer samples treated with varying levels of silica gel, bentonite, and polyvinylpolypyrrolidone. The results showed agreement in the patterns but some differences in the levels. It ap pears that the BPR method gives a different perspective on beer haze stabil ity that should not be influenced by the level of endogenous polyphenol.