Preparation Of Glutamic Acid-Xylose Maillard Reaction Intermediate And Its Processing Flavor

Maillard reaction intermediates are some intermediates generated during the Maillard reaction process.Among them,Amadori rearrangement product?ARP?is regarded as a kind of important Maillard reaction intermediates due to its stable physicochemical properties at room temperature.ARP itself does not show smells but ARP could coutinue Maillard reaction and generate pleasant flavor and color after thermal treatment,which gives ARP the potential for flavor-controlled formation.Glutamic acid is a kind of common flavor enhancer in food industry.When Maillard reaction occurs between Glu and reducing sugar,burnt flavor,almond flavor and salty cheese-like flavor could be produced and the flavor quality of baked foods could be improved.In this paper,the Glutamic acid-xylose?Glu-Xyl?Maillard reaction intermediate was prepared by Glu and Xyl and the processing flavor was investigated so as to provide theoretical guidance for the application of Glu-Xyl Maillard reaction intermediate in baked foods to enhance flavor quality.Using cysteine as the indicator,the method of two-step increase of temperature was used to determine the optimal formation conditions of Glu-Xyl Maillard reaction intermediate.The results showed that a large amount of Maillard reaction intermediate was formed with the thermal treatment for 130 min¹50 min at 90°C.After separation and purification by cation exchange resin,mass spectrometry and nuclear magnetic resonance were used for structural identification and the Glu-Xyl Maillard reaction intermediate was determined as ARP named N-?1-deoxy-?-D-xylulos-1-yl?-glutamic acid with relative molecular mass of 279 and molecular formula of C₁₀H₁₇NO₈.The purified ARP was used as standard and the detection method of ARP yield in aqueous medium was established by high performance liquid chromatography coupled with evaporative light-scattering detector?HPLC-ELSD?,which achieved the quantitative analysis of Glu-Xyl ARP.The effect of reaction time on the yield of Glu-Xyl ARP was investigated and results showed that with the increase of reaction time,the yield of ARP increased and then reached the plateau after 140 min.By changing the initial pH and the molar ratio of reactants,it was found that the yield of ARP was relatively higher when the molar ratio of Glu and Xyl was 1:2;and the yield was increased in a higher pH condition.However,the yield of Glu-Xyl ARP was not significantly improved by changing the reaction time,reactant ratio and initial reaction pH.The influence of reaction time of atmospheric pressure reaction and reaction time and water bath temperature of vacuum dehydration on the yield of ARP were analyzed.Results showed that the yield reached 75.11%when the Glu-Xyl mixture was heated at 90°C for 130 min followed by dehydration at 85°C for 15 min under vacuum condition.The yield of ARP was increased by nearly 34 times in this way,providing a feasible strategy for the efficient preparation of Maillard reaction intermediate.The flavor formation capacity of pure ARP,Maillard reaction-vacuum dehydration products?MDPs?,Maillard reaction products?MRPs?and Glu-Xyl mixture were evaluated under simulated baking conditions.Results indicated that when molar concentration of amino group was the same in the four systems,the speed of aroma formation and the amount of volatile flavor compounds in ARP and MDPs were much higher that in MRPs and Glu-Xyl mixture.When the concentration of Glu-Xyl ARP in pure ARP system was the same with that in MDPs system,the type and quantity of volatile flavor compounds detected in MDPs system showed a higher level than that in pure ARP system,which indicated that ARP could continue to react with the unremoved Glu and other Maillard reaction reactive compounds in the system during the subsequent heating process.Therefore,when applied to foods,the MDPs system could present a better flavor enhancement abillity than pure ARP and MRPs.By the addition of different proportions of MDPs into walnut cookie,the flavor and color of walnut cookie samples were investigated through Gas chromatography coupled with mass spectrometry?GC/MS?,electronic nose,color difference meter and sensory evalution.It was found that when the addition proportion of MDPs was 0.3%,the flavor and color enhancement of walnut cookie system was the best.The flavor changes of walnut cookie sample with the addition of MDPs and MRPs were compared during storage and results showed that the addition of MDPs could reduce the flavor loss of walnut cookie during stroge.