Antioxidative Maillard reaction products (MRP) prepared from reducing sugars and free amino acids in cooked ground pork patties

Fifteen preformed Maillard reaction product (MRP) treatments were prepared by refluxing 0.2 M of three individual reducing sugars (glucose, xylose, and dihydroxyacetone) with 0.2 M of five free amino acids (arginine, histidine, leucine, Iysine, and tryptophan) for 20 hr at 100{dollar}spcirc{dollar}C. MRP's were added (3% v/w basis) to fresh ground pork patties prior to cooking and cooked to internal temperature of 68{dollar}spcirc{dollar}C and stored at 4{dollar}spcirc{dollar}C for ten days. Samples were analyzed for malonaldehyde concentration by the TBA test and HPLC method on Days 0, 5, and 10. HPLC procedure was a new procedure. All MRP treatments (except two TBA observations) had lower TBA values and HPLC peak areas than a control group (no MRP added). The four most effective antioxidant MRP treatments according to TBA and HPLC data were xylose-lysine, xylose-tryptophan, dihydroxyacetone-histidine, and dihydroxyacetone-tryptophan. The greatest degree of lipid oxidation occurred during the first five days of refrigerated storage with minor lipid oxidation occurring thereafter. TBA data was significantly correlated (r = 0.96, P {dollar}<{dollar} 0.001) with the HPLC data for all fifteen MRP treatments. HPLC method did not produce any type of "artifacts" during HPLC analysis of samples. A significant interaction (P {dollar}<{dollar} 0.001) existed between reducing sugar and amino acid. Main effects could not be evaluated. The MRP treatments of glucose reacted with lysine and tryptophan; xylose reacted with histidine, lysine and tryptophan; and dihydroxyacetone reacted with histidine, leucine, lysine, and tryptophan all exhibited strong antioxidant activity when compared to the control. The dynamic headspace analyzer (DHA) of the gas chromatography/mass spectrometry unit was an acceptable method for evaluating lipid oxidation in cooked pork patties. Two MRP treatments (xylose-tryptophan and dihydroxyacetone-tryptophan) and a control (no added MRP) were evaluated on the DHA/GC/MS unit and samples were analyzed on Days 0 and 5. TBA test was conducted on the cooked meat samples used in the GC/MS analysis. The two MRP had significantly lower (P {dollar}<{dollar} 0.05) concentrations of hexanal, pentanal, and total volatiles on Days 0 and 5 when compared to the control. The control had a greater number of secondary oxidation breakdown products than compared to either MRP treatment, and the control had the greatest increase of total volatiles for the five day storage period than either of the two MRP treatments tested. TBA values of the control was significantly higher (P {dollar}<{dollar} 0.05) compared to the two MRP treatments. The Day 0 and Day 5 TBA values of the control and two MRP treatments were significantly correlated (P {dollar}<{dollar} 0.05) with pentanal (r = 0.94), hexanal (r = 0.94), 1-pentanol (r = 0.86), butanal (r = 0.90) and total volatiles (r = 0.93).