| 1-Amino-1-deoxy-2-ketoses known as Amadori compounds,are a class of compounds with similar structure and strong polarity.They are the key intermediate products of N-substituted glucosamine Amadori rearrangement in the initial stage of Maillard reaction,which are produced by the reaction of glucose and amino acids.They have no odor in itself and are key nonvolatile intermediates.At present,the related standard products of Amadori compounds are difficult to obtain and expensive.And there were few studies on their antioxidant activity.The correlation between the concentration of Amadori compound and its antioxidant activity in the reaction system was studied in order to optimize the synthesis conditions of Amadori compounds and reduce the cost of the experiment.In order to study whether 1-L-glycine-1-deoxy-Dfructose?Fru-Gly?compound was involved in Maillard reaction to produce aroma in the roasting sesame process.The effect of Fru-Gly compounds on the volatile aroma components of“defatted sesame meal+sesame oil”was studied at 120?and 180?.It provided a theoretical basis for studying the mechanism of Amadori compounds involved in the production of sesame flavor.The results as follows:?1?UPLC-TOF MS-MS method was used to establish a method for the determination of Fru-Gly compounds.The chromatographic separation was carried out on a Shim-pack GIST C18?2.1×75mm,2?m?.The mobile phase was composed of solvent A?acetonitrile with 0.1%formic acid,V/V?and B?0.1%formic acid,V/V?.The flow rate was 0.2 m L/min.Electrospray ionization?ESI?source was applied with the transitions of m/z 76/88 for Fru-Gly compound.The results showed that calibration curves were linear and covered from 0.05-1?g/m L for Fru-Gly compound,and the correlation coefficients was 0.9997.The recovery was in the range of 96.84%-102.84%with RSD value of 1.93%.RSDs of repeatability and precision were less than 3.0%.The method was suitable for the determination of Fru-Gly compounds.?2?Fru-Gly compounds were synthesized by reflux reaction with glucose and glycine as raw materials.The optimum reaction conditions were obtained by response surface method:When the reaction time was 0.9 h,the reaction temperature was 79?and the molar ratio of glucose to glycine was 3.25:1,the concentration of Fru-Gly compounds can reach 58.80?g/m L.?3?The DPPH radical scavenging rate,ABTS radical scavenging rate and reducing power of glucose,glycine,Fru-Gly compounds and glucose-glycine reaction system were determined.The results showed that glucose and glycine had low antioxidant activity and did not change with the concentration.The Fru-Gly compound and mixed system with its presence have some antioxidant activity,and 3 kinds of antioxidant activity gradually increased with the increased of the concentration of Fru-Gly compound.When the reaction time was 1 h,the reaction temperature was 80?and the molar ratio of glucose to glycine was 3:1,the antioxidant activities of the reaction system reached the maximum value.The concentrations of Fru-Gly compounds at different reaction temperatures were significantly positively correlated with the three antioxidant activities,and the correlation coefficients were all greater than 0.98.The concentrations of Fru-Gly compounds at different reaction times and different molar ratios were positively correlated with the three antioxidant activities.The correlation coefficient is more than 0.80.It was shown that the conditions can be optimized by spectrophotometric determination of DPPH radical scavenging rate and abts free radical scavenging rate and reducing force,and the experimental cost can be greatly reduced.?4?SPME-GC/MS method was used to study the effect of different temperature on volatile aroma components of“defatted sesame meal+sesame oil”system.The results showed that with the increase of temperature,the total peak area and number of peaks detected in the reaction system increased first and then decreased.Moreover,at180?,the summation of peak area and the number of peaks were the largest,and 75kinds of peaks were detected.Among them,the relative content of hydrocarbons and their derivatives in the reaction system decreased significantly with the increase of temperature,and the relative content of aldehydes in the total amount was larger,and the relative content of aldehydes increased significantly at first and then decreased gradually with the increase of temperature.In the three reaction systems at 160??180?and 200?,the highest relative content of the compounds was?E,E?-2,4-Decadienal.?5?The aroma components of“defatted sesame meal”were compared before and after the addition of sesame oil.Under the same roating conditions,only 8 kinds of volatile components were detected in the system of“defatted sesame meal”,followed by“sesame oil”?60 species?,and“defatted sesame seed meal sesame oil”?75 species?detected the most volatile components.Compared with the“sesame oil”system,the amount of aldehydes in the“degreased sesame meal sesame oil”system was reduced by 2 kinds.The relative content was also reduced from 87.42%to 79.91%.At the same time,many products of Maillard reaction which were not detected in“sesame oil”system and the products of lipid oxidative degradation interacting with Maillard reaction,such as butylbenzene,pentylbenzene,2-propylthiophene and 2-pentylpyridine were detected.This showed that adding sesame oil to“defatted sesame meal”was helpful to the formation of aroma components.The results showed that the oxidative degradation of fat had an important contribution to the overall aroma production of the reaction system.?6?The effects of Fru-Gly compounds on volatile aroma components of“defatted sesame meal+sesame oil”system was studied by SPME-GC/MS.The results showed that adding a certain amount of Fru-Gly compounds in the reaction system reduced the number and species of volatile aroma components from 44 to 25 at low temperature?120??,and the relative content of aldehydes decreased significantly.The addition of the Fru-Gly compound at a high temperature of 180?increased the relative content of the aldehyde compound and the ketone compound,the hydrocarbon and the derivative thereof were reduced,and the sulfur-containing heterocyclic compound was detected.The results showed that low temperature was not conducive to the pyrolysis of Amadori compounds.Meanwhile,Amadori compounds with antioxidant activity can inhibit Maillard reaction and lipid oxidation degradation. |
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