Insight into non-enzymatic browning of shelf-stable orange juice during storage: A fractionation and kinetic approach.

BACKGROUND: Non-enzymatic browning (NEB) is the main quality defect of shelf-stable orange juice and other fruit juices during storage. Previous studies on NEB focused solely on the soluble fraction of orange juice, regardless of both soluble and insoluble fractions turning brown during extended storage. Up to date, clear evidence of the relative contribution of both fractions to NEB is lacking in literature. This study investigated the contribution of the soluble and insoluble fractions of orange juice, which were obtained by centrifugation and ethanol precipitation, towards NEB during storage. In addition, changes in different NEB related attributes (e.g., AA degradation, browning index (BI), etc.) were quantified and kinetically modeled. RESULTS: Evaluation of color during storage showed that the orange juice and the soluble compound-containing fractions turned brown in contrast to the insoluble fractions. The soluble compound-containing fractions showed exactly the same browning behavior upon storage as the plain orange juice. Based on the kinetic parameters obtained, the degradation of AA, the hydrolysis of sucrose, the increase of glucose and fructose content, and the formation of furfural and 5-hydroxymethylfurfural during storage were similar for the plain orange juice and the soluble compound-containing fractions. CONCLUSION: Considering studies on NEB, this work provided evidence that the soluble fraction of orange juice plays the major role in NEB unlike the insoluble fraction which seems to have no contribution. Furthermore, results from this work demonstrate the potential use of the soluble fraction as an orange juice based model system of reduced complexity in order to further investigate NEB processes. This article is protected by copyright. All rights reserved.