Abstract: Non-enzymatic browning during the storage of cloudy apple juice was caused by the oxidation and polymerization of polyphenols and could be avoided by adding 0.006% VC(W/V)to juice or by storing at lower temperature.The degree of non-enzymatic browning and the loss of polymeric proanthocyanidin,epicatechin,chlorogenic acid and VC of juice increased with the increase of storage time and storage temperature.The color of juice changed much at the initial period of storage and then little.L value decreased,a value increased and b value changed little of the juice.The change of juice color is caused mainly by the oxidation and polymerization of polyphenols and degradation of VC.Free amino acids also contribute to the browning whereas Maillard reaction has little to do with it.The mean dgree of polymerization for polymeric proanthocyanidin also increase with increase of storage time and storage temperature.

Key words: cloudy apple juice, non-enzymatic browning, polyphenol, polymeric proanthocyanidin, VC