| People not only pay attention to the safety and functionality of food,but also pursue the consumption experience of "sensory pleasure" to "pleasant sensory".Nowadays,the commonly used commercial thermal reaction essences are usually made with Maillard reaction products(MRPs),which possess the characteristics of high simulation degree,rich and full aroma.But they revealed defects of flavor escape,bad persistence,flavor contour distortion and difficult standardization during the food thermal processing and storage as well as the terminal kitchen cooking process.Therefore,improving the stability of Maillard reaction essence and regulating the formation of its color and flavor in the expected direction have became a key scientific problem urgently needed to be solved in the food flavor industry.Around this focus,the Maillard reaction intermediates(MRIs)with stable physical/chemical properties and no flavor or color were prepared as the prefabricated base materials to realize the regulation formation of expected fresh flavor and ideal color during food processing.The cysteine-xylose(Cys-Xyl)reaction system with the formation of meat-like flavor and the method of stepwise increased temperature of Maillard reaction were used for the preparation of MRIs.Cys was selected as the effective tracer among the existing compounds confirmed to have inhibitory effect on Maillard browning,and the critical formation conditions for MRIs in aqueous phase were determined.Based on this,two intermediates,2?threityl-thiazolidine-4-carboxylic acid and Amadori rearrangement product(TTCA/ARP)were prepared,purified and characterized.The qualitative and quantitative analysis methods of cysteine-xylose-MRIs were established using HPLC-ELSD,and the accuracy of the stepwise increased temperature of Maillard reaction method was verified by quantitative analysis.The targeted intermediates traced by Cys were identified as TTCA.It was found that the tracing effect on TTCA intermediates was better at low temperature and under neutral or weakly acidic conditions during the low temperature reaction stage,and the high temperature as well as alkaline environment during the high temperature reaction stage.The derivatization method and chromatographic analysis were used to clarify the influence of Cys on the formation of characteristic downstream products which were active browning precursors during the TTCA degradation pathway,pointing out the possible reaction targeting nodes that cysteine may act on,and preliminarily proving the tracing principle of cysteine on the formation of TTCA by inhibiting or blocking the formation of browning polymer: cysteine could directly act on TTCA at relatively high temperature(120℃)to reduce it to the substrate sugar and amino acid and decrease the formation of active browning precursors as well as block the formation path of chromatic substances,and thus tracing the formation of intermediates according to the lowest point of browning intensity.The glutathione was used as the tracer in the method of stepwise increased temperature of Maillard reaction to further confirm the important role of free thiol groups in the tracer process.The method of thermal reaction-vacuum dehydration was used for the preparation of Cys-Xyl Maillard intermediates.Results showed that the vacuum dehydration was the key step to promote the conversion from substrate Cys-Xyl to N-substituted D-xylosamine as well as TTCA.The TTCA yield could reach the maximum of 79.78% as the water content reached almost 0%;The chemical balance kept moving downstream with the prolongation of dehydration time,and the downstream α-dicarbonyls increased continuously,but the reaction process still remained in the early stage and TTCA was still the main intermediate generated through the method of thermal reaction coupled with vacuum dehydration.The mechanism of water content,water activity and water presence status on the yield of TTCA was clarified,and confirmed that the dispersation of free water and immobilized water was the key driving force for facilitating the movement of reaction balance of Maillard reaction in the direction of TTCA/ARP formation.During the dehydration process,the serious phenomenon of samples sticking to the wall appeared with the increasing concentrations,and the problem of uneven heating caused by this was not beneficial to the preparation of ideal Maillard intermediates.This chapter used instantaneous high temperature dehydration of spray-drying to realize the selective preparation of MRIs with different TTCA/ARP ratios.Meanwhile,the specific transformation from substrates to intermediates(TTCA,ARP)during the high temperature instantaneous dehydration process of spray drying was clarified.It could be found that the increase of temperature promoted the conversion from TTCA to ARP to reach a certain extent,changing the chemical balance between these two compounds.At this point,ARP could account for 23.75% of the total formation of Maillard intermediates.On this basis,properly regulating and increasing the p H values of spray-drying solutions could further promote the balanced conversion from TTCA to ARP,and the ARP amount even accounted for 59.48% of MRIs generation when p H increased to 9.5.The promoting effect of the spray-drying dehydration process on the formation of intermediates was further clarified through the changes of their water presence state,results revealed that high temperature instantaneous dehydration process could significantly remove the free water in the system and decrease its water activity,enhancing the transformation from N-substituted D-xylosamine to Schiff base.The contents of downstream α-dicarbonyls confirmed that the spray-drying process might improve the total yield of MRIs while inhibiting the secondary degradation of MRIs under high temperature conditions.Additionally,the functional characteristics of TTCA and ARP including storage stability,formation rules of thermal processed flavor and color were further explored.TTCA revealed better storage stability than ARP;Low temperature,neutral p H,and low water activity were beneficial to the storage of the intermediates;High temperature,too high or too low p H and wet environment will accelerate its degradation and change its appearance and processing quality.The results showed that both TTCA and ARP had the ability to form fresh thermal processed flavor and revealed the same flavor profile,but the volatile flavor and browning formed by heat-treated TTCA intermediate were not as fast as that of the ARP intermediate.Therefore,the selective preparation of Cys-Xyl Maillard reaction intermediates with different TTCA/ARP ratios was valuable to regulate their food processing adaptability.The present study systematically analyzed the dynamic variation rules of flavor and flavor precursors during the thermal degradation process of TTCA intermediate,confirming that the TTCA degradation product revealed the high intensify of flavor formation,but some characteristic flavor compounds were lacked.It was also found the fact that the dehydradtion of deoxyosones took the dominant role comparing to the retro-aldoliazation of deoxyosones,and the asynchronism between the formation of regenerated Cys and retro-aldolization products of deoxyosones might also cause the absence of characteristic flavor components.The results showed that increased temperature and p H could accelerate the TTCA degradation as well as the browning formation,and partially compensated for the lack of characteristic flavor during TTCA thermal degradation.Based on the established model reaction system of TTCA-Xyl,the isotope labeling technique was applied to confirm that the the added Xyl could trap the Cys released from the decomposition of TTCA and formed regenerative TTCA and subsequent new regenerative Cys,which could promote the movement of chemical equilibrium and gradually accelerate the degradation rate of TTCA as well as the downstream products including some α-dicarbonyl compounds and melanoidins formation.The higher p H value could even promote this trapping effect.Results showed the fact that extra-added Xyl captured the regenerative Cys and the circulating formation of regenerative Cys could promote the movement of chemical reaction balance,release the asynchronization between regenerated Cys and generated short-chained active α-dicarbonyls compound,improving the probability of Strecker degradation reaction to form characteristic sulfur-containing compounds and pyrazines.The increase of temperature could even strengthen the occurrence of this phenomenon.The isotopic labeling technique was further used to confirm the synergistic mechanism of additional Xyl and elevated temperature.Based on the action mechanism of extra-added Xyl on the TTCA thermal degradation pathway,this study also explored the heat treatment of MRIs-Xyl precursor simulating the cooking process of braised pork in brown sauce to clarify its processing adaptability.The optimal release of flavor and ideal color formation through the thermal processed MRIs precursors simulating the actual cooking process of braised pork were realized through the regulation of addition amount of Xyl and different ratios of TTCA/ARP.In this study,the influence of different kinds of additional amino acids on the formation of flavor compounds derived from TTCA thermal processing was explored,and the regulation law and mechanism were further clarified.Series model experiments revealed that,in the mixture of TTCA and Cys,additional Cys and its thermal degradation products could trap the browning precursors including MGO,GO and Furfurals rapidly to form characteristic flavor compounds.Therefore,TTCA-Cys could act as controlled formation flavor base with the effect of color inhibition and flavor enhancement.The processing adaptability of prepared TTCA-Cys precursor base simulating the cooking process of clear soup hot pot system was explored,confirming that the mixture of TTCA and Cys with the molar ratio of 1:1.5 could realize the continuous release of flavor and almost bring no significant color change to the systems during the simulated reaction process.The research on the effect of other kinds of additional amino acids excect for Cys on the thermal processed color and flavor of TTCA was also performed.It was found that the addition of glycine(Gly),glutamic acid(Glu)and lysine(Lys)could significantly contribute to the characteristic meat flavor formation through sensory evaluation,and different amino acids could significantly enhance the browning of TTCA thermal reaction systems.The types and contents of flavor substances generated from thermal processed TTCA intermediates mixed with these three kinds of amino acids were determined and the results confirmed that the main influencing factor limiting the formation of sulfur-containing flavor substances wereα-dicarbonyls.The addition of amino acids could promote the movement of chemical balance of the reaction system and keep the content of characteristic flavor precursors in a sufficient state.The TTCA could be mixed with Gly,Lys and Glu to prepare the flavor base with deep process color to improve the flavor,color formation quality of TTCA and improve its food processing adaptability,broaden its application scope in the food industry. |
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