FORMATION OF PROTEIN-POLYPHENOL HAZE IN BEVERAGES

Protein-polyphenol hazes form in beer, wine, and fruit juices and can limit shelf life. Haze-active protein is higher in beer than the other beverages. Haze-active polyphenol is highest in apple juice and red w ines, variable in grape juices, and low in beer and white wine. A syst ematic study of factors that influence haze formation was carried out in a model system. Pectin, arabinogalactan, and poly(galacturonic acid ) led to increased haze while free amino acids and other carbohydrates had no effect. Maximum haze occurred near pH 4 with less haze at high er and lower pH's. As ethanol concentration increased near pH 4, the h aze at first declined, but further increases in ethanol led to increas ed haze. It appears that haze formation is similar in all the beverage s examined and may be explained by a single mechanism. This has implic ations for analysis of haze-active constituents and beverage stabiliza tion.