Formation Mechanism And Control Of Maillard Reaction Derived Hazards-Methylimidazoles

Maillard reactionderived hazards is a research hotspot in the field of food safety, methylimidazoles have attracted global attention. Methylimidazoles existing in processed foods are mainly 2-methylimidazole and 4(5) - methyl-imidazole. This reasearch started with the simultaneously detection of methylimidazoles in foods. On the basis of extensive market research, glucose-ammonia was choosen as a model reaction system, meanwhile, FeSO4, Na2SO3 and amino acid (Glycine, Lysine, Cysteine) were used as inhibitor to explore the formation and inhibition of the Maillard reaction derived hazard-methylimidazoles and the influential factors, in order to provide a theoretical basis and practical guidance to control 4(5) -methylimidazole effectively in caramel industry, especially ammonia caramel manufacturers inindustrial application.The main findings were as followed:1. The analytical method of ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS) for the quantification of 2-methylimidazole and 4(5)-methylimidazole simultaneouslywas developed. The method was validated by evaluating its sensitivity, linearity, and recovery in food samples. The limit of detection (LOD) values of 2-methylimidazole and 4(5)-methylimidazole were 0.5?g/kg and 1.4 ?g/kg, respectively. The recovery of the method ranged from 82.8% and 100.4% for 2-methylimidazole and 94.1% to 108.1% for 4-methylimidazole. The intraday precision of 2-methylimidazole and 4-methylimidazole were 1.3?4.5% and 1.0?5.0%,while the inter-day precision of them were 1.3?4.5% and 1.9?6.5%.The results indicated that the method was suitable for determining 2-methylimidazole and 4(5)-methylimidazole contents simultaneously in food matrices.This method was applied to determine2-methylimidazole and 4(5)-methylimidazole contents in more than 90 kind of commercial foods.The results indicated that the content of 2-methylimidazole was extremely low, however,4(5)-methylimidazole was found in various food including sauce, coffee, cola, tea, cookies, etc, with relatively high content level.This study also revealed the existence of 4(5)-methylimidazole in different varieties of tea for the first time.2. The formation of 4(5)-methylimidazole was studied in model system consist of glucose and ammonium hydroxide.The relationships between reaction temperature, time, substrate constitution and 4(5)-methylimidazole formation were investigated. The results indicated that the above factors were closely related to the formation of 4(5)-methylimidazole.The experimental design was performed by the response surface methodology (RSM),through choosing temperature, time and molar ratio of substrates as the parameters.Results showed that the maximum amount of 4(5)-methylimidazole could be generated when the model system was designed to be a mixture of glucose (0.73 mol/L) and ammonium hydroxide (0.95 mol/L) heated at 148? for 70 min.Such carbonyl-amino condensation reaction was choosen as the model system for studying the inhibition of 4(5)-methylimidazole formation.3. FeSO4, Na2SO3 and amino acid (Glycine, Lysine, Cysteine) were selected to be the potential inhibitors and relevant assays were conducted to compare their inhibitory rateon the formation of 4(5)-methylimidazole in model system.Glycine was identified as the best inhibitor considering both the inhibitory rate of 4(5)-methylimidazole formation and its effects on commordity value such as salt tolerance, color and flavor. The optimum addition level was 0.2 mol/L in the model system.The effect of glycine on the kinetics of 4(5)-methylimidazole formation in model system was described by the Logistic-exponential kinetic model. Results revealed that glycine played its role mainly onreducing the formation of 4(5)-methylimidazole as competitive inhibition agentinstead of its degredation.The research established the UPLC-MS/MS method to simultaneously detect 2-methylimidazole and 4(5)-methyl imidazole. Higher level of was found in most of the commercially available food samplesin the survey. Screened out as the best inhibitors, glycine was able to inhibit 4(5)- methyl imidazole formation by up to 50% when it was added at appropriate amount of 0.2 mol/L.Meanwhile, it would not bring about muchnegative influence on the quality of the final product,on the contrary, would enhance the (red) color value.Given that glycine is wildly used food additives witha favorable cost-effective,there would be no obstacles in laws and regulations for its application in caramel production.Furthermore, there needsno change in processingtechniques or parameters, also no additional equipment investment. As can be concluded, glycine has bright prospects in caramel manufacting. The research provided a solution to reduce the risk of Maillard reaction derived hazard-methylimidazole in foods.