Role of sugar–amino acid interaction products (MRPs) as antioxidants in a methyl linoleate model system

Effects of early Maillard reaction products (MRPs) as antioxidants in methyl linoleate model system, during refrigerated storage at 5 °C for 6 days, have been evaluated. MRPs were prepared by reacting glucose with five different amino acids – glycine, methionine, tryptophan, aspartic acid and lysine – using two different concentrations and time intervals (30 mM/1 h, 30 mM/2 h, 60 mM/1 h and 60 mM/2 h). The preformed MRPs were incorporated, after studying pH and optical density profile, in a model system comprised of methyl linoleate and microcrystalline cellulose. Antioxidative characteristics were evaluated by estimating the thiobarbituric acid-reactive substance value (TBARS) and peroxide value (PV) and monitoring the gas chromatographic degradation pattern of methyl linoleate immediately after heating, as well as after storage at 5 °C for 2, 4 and 6 days. Analysis of variance revealed highly significant differences among TBARS, PV and the % of methyl linoleate degradation (p < 0.01) values, both initially and during storage in glucose + lysine and glucose + glycine with respect to control. Other treatments, such as glucose + methionine and glucose + tryptophan exhibited moderately significant differences (p < 0.05). But glucose + aspartic acid was not significantly different (p > 0.05) Significant differences were observed between 60 mM/2 h and 30 mM/1 h of MRPs with glucose + lysine and glucose + glycine (p < 0.01). Out of the five combinations tried, glucose + lysine and glucose + glycine exhibited good antioxidative potential at 60 mM/2 h. The % of antioxidant activity was in the order 60 mM/2 h > 60 mM/1 h > 30 mM/2 h > 30 mM/1 h for the treatments glucose + lysine > glucose + glycine > glucose + tryptophan > glucose + methionine > glucose + aspartic acid, respectively.