| In the processing of food and other products,Maillard reaction is a common reaction which leads to changes in color and flavor.Color can affect people’s perception of flavor,and it is often used as one of the indicators for quality evaluation.Although there are lots of studies on the color substances and aroma components generated by the Maillard reaction,the relationship between the color and the flavor in the reaction still needs further investigation due to the complexity of the reaction routes.In this paper,glucose with glycine,proline and phenylalanine were selected to establish the Maillard reaction model systems for the preparation of melanoidins and the separation of color substances.The influence of color substances on the formation of volatile components during heating was investigated.The main research contents and results are as follows:(1)Preparation of Maillard reaction products and determination of the color charactertistics.The Maillard reaction products were prepared from glucose with glycine,proline and phenylalanine,respectively.The color of the Maillard reaction products were comprehensively characterized by measuring the UV-visible spectral and CIE color characteristics;calculating the browning index,color intensity and hue;and determining the color dilution factor with the sensory evaluation method.Among three samples,the sample from the glycine reaction system had the highest browning index and color intensity with the darkest color;the sample from the proline reaction system had the highest absorbance value at 460 nm;while the sample from the phenylalanine reaction system had the lightest color and exhibited a more yellowish color than the other two samples.(2)Gel chromatography column separation of the Maillard reaction products.The color characteristic,spectral property,elemental composition,relative molecular weight and pyrolysis property of the separated samples were determined.The color of the separation products from the reaction system containing glycine were the darkest,and the color of the separation product from the reaction system containing phenylalanine was the lightest.The infrared spectra showed that the main color substances of each of the three reaction systems had similar chemical groups.The color components had good thermal stability and the pyrolysis products mainly generated at the temperatures above 300~°C.Three common pyrolysis products(2,5-dimethylfuran,2-methylpyridine and 2-methyl-1H-pyrrole)were identified in all samples.(3)C18 column separation of the main color components.The color characteristic,spectral property,elemental composition,relative molecular weight and pyrolysis property of the separated samples were determined.In the glycine reaction system,it was found that the medium molecular weight chromophores with an average molecular weight of about 6000 Da to 9000 Da contributed more to the overall color.After C18 column separation,the content of oxygen in each color components increased,while the N/C ratio decreased,meaning that the percentage of structures from glucose derivatives increased.Glucose derivatives(2,5-dimethylfuran and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one)were identified in the products from three reaction systems,and these derivatives may be involved in the melanoidin skeleton.(4)Structural characterization of the color components.The structural characteristics of the C18 isolated fractions were further investigated by Fourier transform infrared spectroscopy(FTIR),matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS),and nuclear magnetic resonance spectroscopy(NMR).A series of peaks with a difference of about m/z 58 were found in the samples of the reaction system containing glycine,indicating that a regular structure might be formed in the melanoidin skeleton with the participation of glyoxal.In the MALDI-TOF-MS spectra and 2D NMR HSQC spectra of the three reaction systems,signals presented in the same range,respectively.This result further suggested that glucose may have generated some similar derivatives in the Maillard reaction systerms involving different amino acids. |
