美拉德反应（Maillard reaction）Quote: what is the virtue response, please? Why didn't you hear about it?Indeed, you can not hear of the virtue reaction, and no one knows what it is.The correct answer is: Maillard reactionMaillard reaction is a universal non enzymatic browning phenomenon. It has been used in the production of food flavor, and it has been in recent years in our country.The application of Maillard reaction in flavor production has been studied in many foreign countries, and there is little research and application in China. This technology has a very good application in meat flavor and tobacco flavor. The essence of the essence of meat with natural flavor, with the deployment of technology can not be compared to the role. The application of Maillard reaction in essence in the field to break the traditional production technology and flavor category, is a new application technology of flavor spices production, worthy of research and extension, especially in condiment industry.1 Maillard reaction mechanismIn 1912, French chemist Maillard discovered that the mixture of glycine and glucose formed brown substance when heated. Later, it was found that such reactions not only affected the color of the food, but also played an important role in its aroma, and called this reaction non enzymatic browning reaction(nonenzimicbrowning) [1]. In 1953, Hodge made a systematic explanation of the mechanism of Maillard reaction, which could be divided into 3 stages, [2 to 4].1.1 initial stage1.1.1 Schiff base formation (ShiffBase): amino acids are heated with reduced sugars, and amino groups are condensed with carbonyl groups to form Schiff bases.Generation of 1.1.2N- substituted amines: cyclization of Schiff bases.1.1.3Amadori compounds are generated: N- substituted sugar amines are rearranged by Amiadori to form Amadori compounds (1 - amino - 1 - deoxy - 2 - keto sugar).The 1.2 intermediate stage is in the intermediate stage, and the Amadori compound reacts through three routes.1.2.1 under acidic conditions by 1,2 - enolization reaction, generate carbonyl methyl furan aldehyde.1.2.2 under alkaline conditions by 2,3 - enolization reaction produced reductone Brown dehydrogenation reductone. Conducive to the formation of Amadori rearrangement products 1deoxysome. It is the precursor of many food aromas.The 1.2.3Strecker reaction of poly solution: proceed cracking reaction, formation of carbonyl and dicarbonyl compounds, to the final stage of reaction or decomposition reaction ofStrecker and Strecker amino aldehyde.1.3 final stageThe reaction is complex at this stage. The mechanism is not clear. The products of the intermediate stage react with the amino group aldehyde group - amino group, and finally produce the black like essence. The products of Maillard reaction belong to the category of black essence, and there are a series of intermediates, ketones and volatile heterocyclic compounds. Therefore, the products of Maillard reaction are not [5].2 factors affecting Maillard reaction [5 ~ 8]2.1 sugar amino structureSugar is the main material of the Maillard reaction, five carbon sugar browning rate is 10 times six sugars, reducing sugars in five carbon sugar browning speed sort: > > Arabia ribose sugar xylose, six carbon sugar: galactose mannose glucose > >. Reducing disaccharide molecular weight, the reaction speed is slow.In carbonyl compounds, aldehyde ethylene alpha browning is the slowest, followed by alpha disaccharide compounds, ketones is the slowest. Amine browning is faster than amino acid. In amino acids, the basic amino acids are slower, and amino acids are slower than proteins.2.2, temperature 20~25 DEG oxidation can occur Maillard reaction. In general, the reaction rate is 3~5 times eachdifference of 10 degrees centigrade. When the temperature is higher than 30 DEG C, the reaction rate is less than that of temperature and oxygen when the temperature is higher than 80.2.3 moisture content in 10% to 15%, the reaction is easy to occur, completely dry food difficult to occur.The 2.4pH value pH value is more than 3, with the increase of pH value and accelerate the reaction.2.5 chemical reagents: acid sulfite inhibits browning. Calcium salts combine with amino acids to form insoluble compounds that inhibit reactions.3 the mechanism of meat aroma formation3.1 precursor substances with meat flavorRaw meat is odorless and has a flavor only when distilled and baked. In the heating process, a series of complex changes in various tissue components in the meat, the aroma of meat, there are 1000 kinds of volatile components were identified, including: lactone compound, pyrazine compounds, furan compounds and sulfides. Studies have shown that precursors of these flavors are mainly water-soluble carbohydrates and amino acid compounds, and phospholipids and three glycerides, such as lipids, [9]. Meat in the heating process, lean meat tissue gives meat flavor, while the fat tissue gives meat products a unique flavor, if the meat from all kinds of meat removed, the smell of meat is consistent, no difference [10].3.2 the Maillard reaction and flavor compoundsNot all of the Maillard reaction can form compounds of meat, but in the process of forming flavor compounds, the Maillard reaction plays a very important role. Flavor compounds are mainly N.S.O- heterocyclic compounds and othersulfur-containing compounds, including furan, thiophene, pyrrole, imidazole, pyridine ring and ethylene sulfide and other low molecular weight precursors. Pyrazine is one of the main volatile compounds. In addition, sulfides play an important role in Maillard reaction products. If the sulfide is removed from the volatile components of the heated meat, the meat flavor is almost gone, [4]. Meat flavor substances can be classified by the following way: amino acids (cysteine, cystine) are reduced by Maillard and Strecker reactions. Sugars, amino acids, and lipids produce meat flavor by degradation. Lipid (fatty acids) producing meat flavor by oxidation, hydrolysis, dehydration, decarboxylation. Thiamine produced meat flavor.A thiol reacts with other ingredients to produce a meaty odor. RNA and DNA - 5 '- phosphate, methyl furan ketone by hydrogen sulfide produced by the reaction of meat flavor. It can be seen that heterocyclic compounds originate from a complex reaction system, and the Maillard reaction plays an important role in the formation of many meat flavoring substances during the formation of meat aroma [11].3.3 effects of amino acids on meat flavor compoundsThe amino acid composition of beef extract before and after heating in the analysis, after heating change is mainly glycine, alanine, cysteine, glutamic acid, these amino acids producedmeat flavors and sugar reaction in the heating process. Pyrazine is a particularly important group of volatile components that heat exudates,About 50%. Another important volatile compounds from meat structure generation analysis of beef in sulfur-containing amino acids, cysteine and cystine and glutathione, is the precursor compounds of beef aroma not less. Cysteine and other sulfur compounds. Strong meat flavor producing cysteine, cystine and methionine have poor taste, potato like flavor, valley cystine produce good meat. When heated with a mixture of cysteine and reducing sugars, a pungent "raw" flavor is obtained, and a more complete and perfect flavor is obtained if other amino acid mixtures are present, which is very suitable for protein hydrolysates.3.4 effects of reducing sugar on meat flavoring substancesIn response, the polysaccharide is invalid, mainly refers to the disaccharide sucrose and maltose, the poor flavor, monosaccharides with reducing power, including pentose and hexose. Studies have shown that monosaccharides have a stronger reactivity than hexose, and that ribose is the most reactive in sugar, followed by Arabia sugar and xylose. Because glucose and xylose are cheap, easy to obtain and have good reactivity, glucose and xylose are commonly used as raw materials for Maillard reaction.3.5 environmental factors impact on the reaction [1]Beef flavor requires a longer time and a thicker reactionsolution. Pork and chicken flavors require shorter heating times, thinner reaction solutions, and lower reaction temperatures. The pH value of the reaction mixture is lower than 7 (preferably 2~6), and the reaction effect is better. When the pH is greater than 7, the reaction is difficult to control and the flavor is poor due to the fast reaction speed. Different kinds of amino acids have more significant effects on flavor characteristics than those of different kinds of sugars. The same amino acids and different kinds of sugars produce different aromas. Different heating methods, such as "cooking", "steaming", "burning", and the different cooking methods, the same reaction substances produce different flavor.4 production of meat flavorFrom the beginning of 1960, there have been studies using various monomer flavor after blending meat flavor, but due to the characteristics of all kinds of cooked meat flavor is very complex, which is difficult to achieve and cooked meat flavor and fragrance realistic level, so the research and utilization of meat aroma precursors of attention. The precursor for the preparation of meat flavor, mainly sugar and sulfur-containing amino acids such as cysteine based, generated by heating the reaction, including fatty acid oxidation, decomposition, thermal degradation of sugars and amino acids, Maillard reaction and produced two or three times reaction etc.. Meat flavor composition formed by the hundreds. With these materials as the foundation, through the harmonic can be made with different characteristics of meat flavor [4]. The formation of the Maillard reaction meat flavor in terms of raw materials or process can be seen as a natural, so the meat flavor can beregarded as a natural flavor.。