A simulation system to study the types and causes of browning in concentrated orange juice during storage

Orange juice is highly popular among consumers for its unique taste, flavor, and nutritional value. However, orange juice is susceptible to browning, resulting in loss of quality. The browning of orange juice is complex, especially non-enzymatic browning (NEB), and its main mechanism has not been reported. In this study, the browning of concentrated orange juice (COJ) was determined to be NEB during storage by detecting polyphenol oxidase and peroxidase activities. A simulation system based on the main components of COJ was established to explore the main mechanisms of NEB. The browning products (5-HMF, A₂₉₄) and browning indexes (BI values, ∆E) of the simulation system showed that the contribution of the Maillard reaction (0.085) to browning was slightly greater than ascorbic acid degradation (0.078) and 28 times greater than caramelization reaction (0.003). This suggests that ascorbic acid degradation and the Maillard reaction are the main factors to NEB of COJ, while the caramelization reaction and phenolic oxidation can be ignored. Moreover, the browning in the early stage of storage was mainly caused by the degradation of ascorbic acid, and the later stage was Maillard reaction. In summary, the browning of COJ during storage is mainly caused by ascorbic acid degradation and Maillard reaction with different stages of action. Developing browning inhibition strategies for COJ should focus on the main browning factors at different stages to regulate browning more precisely and protect the quality.