Characterization of Browning Formation in Orange Juice during Storage

In citrus juice products, non-enzymatic browning is the main cause of quality loss contributing to both flavor and color changes during prolonged storage. Ascorbic acid degradation and the Maillard reaction have been well established as the main pathways involved in juice browning. However, the contribution of reaction precursors and especially the role of reducing sugars has remained unclear. In order to gain a deeper understanding into browning mechanisms, the α-dicarbonyl compounds, key building blocks of non-enzymatic reactions, were characterized and monitored in orange juice during a ten week storage study. Results indicated that the α-dicarbonyl content was significantly correlated to the development of the brown color. More specifically, threosone and 3-deoxyglucosone, respectively C4 and C6 α-dicarbonyls, showed the highest correlation with color formation. Further investigations using isotope model experiments demonstrated the key roles of fructose and glucose and, thus, the significant implication of the Maillard reaction in juice browning. This work afforded a better understanding of non-enzymatic browning in juice products.