Coordinated Construction Of Chicken Broth Flavor Precursors By Maillard Reaction Intermediates With Enzymatically Hydrolyzed And Oxidized Chicken Fat

Savory flavorings are prepared from reducing sugar,amino acids,or enzymatically hydrolyzed animal muscle with refined tallow and other ingredients via thermal reaction at high temperature.The flavorings are of abundant flavor compounds which are volatile easily.Moreover,the defects of fragrance distortion and poor fragrance durability are prominent,especially when they undergo further thermal process.And this defect makes the savory flavorings cannot meet the requirements of downstream food processing enterprises and consumers,which limits the application of savory flavorings greatly.To solve this problem,partial least squares regression(PLSR)was employed to clarify the important precursors affecting the chicken broth flavor.Stable flavor precursors were prepared via the coordination of regulated thermal reaction-vacuum dehydration with the enzymatic hydrolysis-oxidation of lipid.The precursors were of low volatility,stable at room temperature,and could convert into flavor compounds rapidly during thermal process.Then the formation pathways of the flavor compounds derived from the interaction between Maillard reaction intermediates and enzymatically hydrolyzed and oxidized chicken fat was elucidated to establish thermal process flavor precursor with the two.Upon this,other ingredients such as nucleotides,peptides which contributed positively to chicken broth were involved in the construction of chicken broth flavor precursor to obtain chicken broth ingredient which flavor compounds could be controlled in thermal process.To clarify the materials such as amino acids,nucleotides which can be applied in the construction of chicken broth flavor precursors,the characteristic contribution components influenced the chicken broth flavor were analyzed.Results showed that aldehydes and the sulfur containing flavor compounds showed significantly positive contribution to the meaty and fatty attributes of chicken broth via PLSR analysis.Furthermore,the correlation between the sensory evaluation results of chicken broth and the non-volatile flavor compounds in chicken broth was established,finding that glutamic acid(Glu)and glycine(Gly)were proved to be presented positive contribution to the meaty and umami attributes of chicken broth.Considering the important role of cysteine(Cys)in meaty flavor formation,Glu,Gly,and Cys were taken as the characteristic amino acids in chicken broth flavor improvement.Other amino acids such as histidine(His),methionine(Met),and lysine(Lys)were considered as the important amino acids which could enhance the diversity of the flavor compounds.Additionally,nucleotides presented positive contributions to the meaty,umami and kokumi attributes of chicken broth and significantly negative contribution to fatty attribute;the peptide fragments which molecular weight less than 1000 made positive contributions to meaty and fatty attributes of chicken broth.Maillard reaction intermediates were prepared and strategy aimimg at improving the yield of Maillard reaction intermediates was proposed based on the explicition of characteristic contribution components in chicken broth.The corresponding Amadori rearrangement products(ARP)of the key amino acid components were prepared at a relatively low temperature followed by their structure identification and characterization.Due to the low yield of ARP,the method of improving ARP yield was investigated via kinetic models,aiming at preparing abundant ARP rapidly.Kinetic models revealed that the formation of ARP followed zero order kinetic model at 100℃,and its formation rate was the fastest and the reaction rates of secondary reactions were relatively slow.The formation pathway of ARP became complicated at higher reaction temperatures:the first order kinetic model could be fitted well at 110℃,while both the models could not be fitted well at 120℃,and the degradation of ARP was more severe at the two temperatures.On the basis of the rapid formation rate with a relatively slow degradation rate of ARP,vacuum dehydration was executed and improved ARP yield significantly.However,excessive dehydration made ARP degraded into α-dicarbonyl compounds which further aggregated into melanoidin or other advanced Maillard reaction products,leading to the ARP yield decreased.The regulated thermal reaction condition of Gly-Rib ARP was:100℃,60 min,the vacuum dehydration condition was:80℃,20 min,and the yield reached 64.5%which increased by 82.8 folds compared with low temperature thermal reaction.When the strategy was applied to the glutamic acid-ribose(Glu-Rib)and cysteine-ribose(Cys-Rib)systems,the regulated thermal reaction condition of Glu-Rib ARP was:100℃,150 min,the vacuum dehydration condition was:80℃,15 min;the regulated thermal reaction condition of 2-threitylthiazolidine-4-carboxylic acid(TTCA,the main Maillard reaction intermediate of Cys-Rib)was 100℃,45 min,the vacuum dehydration condition was:90℃,10 min.The yield of Glu-Rib ARP and TTCA reached 52.9%and 74.8%which increased by 96.1 and 7.28 folds,respectively.The effect of the additional amino acid species on the thermal process flavor of ARP was studied,and the corresponding regulation mechanism was also elucidated.Other amino acids contributed positively to chicken broth flavor were grouped as acidic,neutral,and basic amino acids based on their isoelectric points.For Gly-Rib ARP systems,the monoanion of additional glutamic acid at pH 7.5 acted as nucleophile and the nonionized amino group of additional lysine were involved in α-dicarbonyls formation,favored pyrazines formation in the ARP model.For Glu-Rib ARP system,pyrazines were detected in all systems with additional amino acids except for with additional Gly,due to the nucleophilicity of carboxyl group on Glu.For TTCA system,the formation of the flavor compounds was owing to the degradation of Cys which caused the shift of reaction equilibrium.And this led to sufficient α-dicarbonyl compounds which was related with pyrazines formation.Considering the richness of flavor compounds,the overall profile of the flavor compounds derived from thermally processed ARP was better with additional Met and Lys.Furthermore,the interaction of the three ARPs and their contribution to the thermal process flavor were elucidated.It was found that high ratio of Glu-Rib ARP and Gly-Rib ARP made the accumulation of furans in the thermal reaction system,while excess Gly-Rib ARP led to the the diversity of flavor compounds decreased;Cys degraded from TTCA could further convert into H2S,which made the flavor of the system present sulfur odor.When Glu-Rib ARP,Gly-Rib ARP,and TTCA were mixed following the molar ratio of Glu,Gly and Cys in chicken muscle,higher concentration of flavor compounds was formed compared with the single ARP system.Comparison between the flavor compounds derived from unpurified ARP and mixtures of ARP+Rib+amino acids(equimolar amino group and carbonyl group to ARP)revealed that the thermal process flavor of unpurified ARP enhanced flavor richness and proved the necessity of adding exogenous Met and Lys to the unpurified ARP.The composition of Maillard intermediate thermal reaction flavor precursors was:the concentration of Glu-Rib ARP,GlyRib ARP,TTCA,Met and Lys were 42,12,3,2.5 and 2.5 mmol/L,respectively.Enzymatic hydrolysis-oxidation of chicken fat was employed to realize the controllable oxidation of chicken fat aiming at solving the uncontrollability of chicken fat flavor at high temperature oxidation.The formation pathways of the flavor compounds derived from the interaction of ARP and enzymatically hydrolyzed and oxidized chicken fat(EOC)were studied,revealing that the main flavor compounds derived from ARPs were 2-methylfuran,furfural,4methylpyridine,2-methylpyrazine,dimethyldisulfide,dimethyltrisulfide,2((methylthio)methyl)furan,and 2-acetylthiazole.The main flavor compounds derived from EOC were hexaldehyde,hepenal,octenal,nonenal,decenal and 2,4-decadienal.And 2propylpyrazine,2-pentylpyridine,2-hexylthiophene and 2-propionylthiophene were derived from the Maillard-lipid interaction.Based on the effect of volatile flavor compounds on the overall profile of ARP+EOC,the addition amount of EOC into ARP was determined as 1%to construct the chicken broth flavor precursor(CBFP).After the the construction of Maillard reaction intermediates with enzymatically hydrolyzed and oxidized chicken fat thermal reaction flavor precursor,the effects of nucleotides,and different kinds of Millard peptides on the flavor of the mixture of ARP and EOC were analyzed and the chicken broth flavor precursor system was constructed.It was found that the amounts of sulfur containing and nitrogen containing flavor compounds were increased when the Maillard peptides were added into the CBFP.Comparison among the sensory evaluation of different Maillard peptides proved that sunflower Maillard peptide showed better umami enhancing effect,and could promote the meaty and fatty attributes of CBFP significantly.The effect of different reaction state sunflower Maillard peptide on the flavor of CBFP was studied.The flavor profile of CBFP with sunflower peptide which underwent Maillard reaction for 30 min resembled natural chicken broth.The composition of CBFP was as follows:according to dry matter,Glu-Rib ARP took up 39.4%,Gly-Rib ARP took up 8.3%,TTCA took up 2.5%,Met took up 1.25%,Lys took up 1.25%,enzymatically hydrolyzed-mildly oxidized chicken fat took up 33.6%,sunflower Maillard peptide took up 13.4%,and I+G took up 0.3%.The CBFP was prepared at 120℃,120 min,and it could be used in fried chicken steak,barbecue,chicken flavored potato chips,fried chicken pie and chicken soup hot pot and other products.