Metallic components of fruit juices. I.—Copper as a factor affecting sedimentation in bottled apple juices

摘要

AbstractStorage deposits in bottled pasteurized apple juices have been found to consist mainly of degraded juice phenolic compounds, protein material and ash components. The presence of copper in low concentrations promotes sedimentation and leads to the formation of deposits of high copper content: the effect of copper is partly inhibited by the presence of sulphur dioxide. Of the other metals tested only tin was found to increase sedimentation and to appear in significant amounts in the deposits. Studies of juice components in isolated systems suggest that the presence of copper is a main factor in deposit formation and that copper catalyses the degradation of juice phenolic substances, particularly of leucoanthocyanins andepi‐catechin, leading to their precipitation. A comparison is drawn between the storage deposits of apple juices and the non‐biological hazes of b