First pasteurization of the raw juice may inactivate or denature polyphenoloxidase (PPO), so in the following processing and storage, accumulation of brown color is mainly due to Maillard reaction.

• 苹果浓缩汁加工单元操作中前巴氏杀菌杀处理能够钝化PPO的活性，在前巴氏杀菌后的加工单元操作及贮存过程中引起果汁褐变的主要原因是美拉德反应。