STUDIES ON THE MECHANISM OF ACTION OF COPPER FINING AGENTS (κ CARRAGEENAN)

Abstract

Carrageenan mediated clarification of brewers' wort comprises two reactions: interaction between carrageenan and soluble wort polypeptides and flocculation of particulate material. The dose/response characteristics of interaction between carrageenan and soluble polypeptide material suggested that carrageenan exhibits selectivity with respect to specific polypeptide fractions. Size exclusion chromatography of worts demonstrated that carrageenan treatment resulted in reductions in fractions of relative molecular mass Mr 70 000, 40 000 and 12 000. Fining trials demonstrated that the reactivity towards soluble polypeptides is independent of the presence of insoluble particulate material. Furthermore, both interaction with soluble polypeptides and flocculation of particulate material occurred in systems fined under high (80°C) and low (20–25°C) initial temperatures and this suggested that the presence of carrageenan in a helical conformation is essential to fining action rather than conformational transitions in polysaccharide structure. Additionally, carrageenan has no effect on the levels of low molecular mass wort solutes such as nucleic acid derivatives, aromatic and heterocyclic amino acids.