Antibrowning activity of MRPs in enzyme and fresh-cut apple slice models

The present study examined various types of Maillard reaction products (MRPs) for their inhibitory effect on mushroom tyrosinase. Results showed that monosaccharide-GSH (glutathione) but not polysaccharide-GSH derived MRPs were more active than GSH in inhibiting mushroom tyrosinase. However, in fresh-cut apple slice model, surprisingly GSH performed much better than sucrose-GSH derived MRPs when the apple slices were stored at room temperature for 24 h. Further time-course study did find deterioration in tyrosinase mushroom inhibitory activity of sugar-GSH derived MRPs over time, suggesting the formed tyrosinase inhibitors in MRPs are unstable. Different combinations of chemical agents with sucrose-GSH derived MRPs were also investigated on apple slices. A synergistic effect was observed when sucrose-GSH derived MRPs (3.125 mM) were applied in combination with 0.5% ascorbic acid. Apart from instability of principal inhibitors, observation of an unpleasant odor from apple slices treated with MRPs raised another concern about the probable negative impact of these inhibitors on the sensory quality of food products. Our research indicates the limited application of MRPs as antibrowning agents for food products. (C) 2008 Elsevier Ltd. All rights reserved.