Evaluation of Rapid Colloidal Stabilization with Polyvinylpolypyrrolidone (PVPP)

Abstract

Several colorimetric, chromatographic, and nephelometric tests were compared as tools for monitoring the rapid (<3 days) colloidal stabilization of lager beers by a combination of cold filtration at −1°C and treatments with polyvinylpolypyrrolidone (PVPP). No significant changes in composition were detected during storage of beer for seven days at −1°C prior to filtration on a bench scale. The effects of dosage on a pilot-scale with different amounts of recoverable PVPP (10–50 g/hl) or single-use PVPP (10–20 g/hl) on total polyphenols, total flavanols, simple flavanoids, protein sensitivity, alcohol-cooling haze, and tannoids were compared with concomitant changes in colloidal stability, as revealed by accelerated aging at both 37 and 60°C. Close correlations were found between the results of the haze forcing tests and all tests other than the tannoid measurement made on freshly bottled beers. Although decreases in the contents of the simple flavanoids related most closely to improvements in colloidal stability, the alcohol-cooling test was also a useful indicator of stabilization effectiveness. The colloidal stabilities of beers aged at 37°C were related to both the amounts of simple flavanoids that were oxidized during aging and also to the contents of tannoids in the aged beers. Treatment with recoverable PVPP at the highest rate effectively stabilized the sample beer by adsorbing both the simple flavanoid precursors of chill haze and the tannoid components of protein-polyphenol complexes.