If browning is assumed to be mainly related to the activity of the enzyme pool (POD and PPO, with pKs equal to 3.2 and 3.1, respectively), results Fig. 6. Prediction of the browning litchi pericarp during storage at 10 ◦ C after different postharvest treatments with acids and chitosan (browning index grade:: BI=1; : BI=2; : BI=3; : BI=4; and: BI = 5). obtained confirm the hypothesis of a substantial decrease of enzymatic activity in vivo and/or a sta-bilization of anthocyanins at epicarp pH values close to 3.0.