CARRAGEENAN MEDIATED CLARIFICATION OF DIALYSED WORT SYSTEMS

Fining trials with kappa-carrageenan in dialysed wort demonstrated that potassium or calcium cations were essential for the flocculation of non-microbiological particulate material. The relative ability of metal cations to promote flocculation followed identical trends as established for carrageenan helix stabilising action and gelation (K⁺ > Ca²⁺ > Na⁺). Carrageenan also exhibited interaction with soluble wort polypeptides, in particular fractions of relative molecular mass (Mr) 70 000 and 40 000. This interaction occurred in the absence of added metal cations and was suppressed by increasing concentrations of potassium or calcium. Addition of sodium ions to systems containing potassium had no effect on either interaction with soluble polypeptides or the flocculation of particulate material. Decreasing the pH of dialysed wort impaired flocculation reactions but enhanced removal of soluble wort polypeptides. These results suggest that reaction between carrageenan and soluble polypeptides occurs via electrostatic interactions whereas flocculation of particulate material requires the presence of carrageenan in a helical conformation.