| Non-enzymatic Browning reaction(NEBR) refers to the production of melanoidins without enzymes, which involves in a series of process of oxidation and polymerization, including Maillard reaction, ascorbic acid browning and caramelization reaction. Maillard reaction is one of the most important and it is a type of condensation reaction between carbonyl group and amino group, generating volatile compounds and macromolecules brown melanoidins and having a significant influence on color, nutrition and flavor of food. Non-enzymatic browning reaction process is extremely complex with low quantity and unstable products, which results in great difficulty in tracking a certain stage or exploring the formation mechanism of a certain production. The kinetics method is commonly to understand the reaction mechanism of NEBR and is to control the progress of the reaction, which makes the reaction toward a favorable direction.L-ascorbic acid(L-ASA), including potential carbonyl group after the traditional reducing sugar, is one of the compounds, which is closely related to people’s life and makes the study become more practical and valuable. In the paper, the NEBR and Maillard reaction were researched about L-ASA, L-ASA and kinds of amino acid. Firstly, the influence of parameters including time, temperature and p H on the self-degradation process, the kinetics characteristic and the possible degradation mechanism of the degradation of L-ASA was researched. Secondly, Maillard reaction based on the L-ASA and glycine was studied, especially the effects of micro environment condition on the residual concentration of reactants, colorless intermediates, browning products, volatile and the mechanism of the volatile substances were researched. And the kinetic characteristics were also discussed. Finally, Maillard reaction between L-ASA and neutral / basic amino acid was researched, the trend effects of reaction factors on the Maillard were gained. The main research contents are as follows:1. The NEBR of the self-degradation of L-ASA was researched.The influence of different factors, including time, temperature and pH on the self-degradation of L-ASA was discussed, and the degradation of L-ASA, the formation of un-color intermediates products(UIPs), browning substances(BPs), volatile products(VPs), the dynamics characteristics and the possible degradation mechanism of the self-degradation of L-ASA were researched. The results showed that the different effects of parameters on the self-degradation of L-ASA, especially with the most significant by solution condition.The degradation of L-ASA was stimulated when the pH was 6.8, which conducived to the formation of BPs and the major VPs were furan and ketones in the degradation process of L-ASA; the UIPs were stimulated when the solution environment pH was 4.5 and the furfural and 2,2′-methylenebisfuran were the main VPs.The degradation characteristics of ASA followed the first-order kinetics. However, the formation rate of UIPs and BPs was according with zero-order kinetics under various solution environment conditions.2. The reactants consumption was researched based on Maillard reaction of L-ASA/glycine. In the system, the effects of solution condition, which were the reaction temperature, time and the initial pH of solution on the system, were discussed and the dynamics characteristics were analyzed. The results showed that increasing temperature and longing time would be beneficial to the degradation of L-ASA, and the solution environment condition had a remarkable influence on the Maillard reaction of L-ASA/glycine, the degradation of L-ASA would arrive at the maximum when the solution pH was 4.5; however, the various parameters had less effect on the consumption of glycine.The degradation kinetics of L-ASA was still according to the first order based on the consumption of L-ASA when reaction time, temperature and pH value was changed.3. The formation of UIPs, BPs, VPs based on Maillard of L-ASA/glycine was discussed. The effects of various parameters on the products, the kinetics characteristics and the mechanism of the VPs were researched. The results showed that the yields of UIPs and BPs would be increased as increasing temperature and extending time, even more, the reaction mechanism would be affected by reaction conditions directly. The UIPs and BPs were stimulated when the pH was 4.5. The major VPs were furfural or a kind of furfural and at low temperature the formation of furfural could be carried out; pyrazines and the derivation ofpyrazines were the major VPs in alkaline conditions and the quantity of pyrazine derivation compounds was less at low temperature, the derivation of pyrazine would be increased with increasing temperature and extending time in basic solution condition. When the initial solution environment pH was 8.0, the amounts of derivation of pyrazines reached the maximum. The formation kinetics of different products was following the zero order and would be affected by the solution pH. To study the reaction mechanism of L-ASA and Glycine, we found L-ASA would be decomposed firstly and then react with ammonia, which released by Glycine.4. The NEBR of L-ASA and neutral/basic amino acids was researched. The neutral amino acids were tryptophan, threonine and basic amino acids were lysine, arginine, histidine, respectively. The effects of various time and temperature on the formation of UIPs and BPs were discussed. The results showed that the yield products would be increased with increasing of reaction time and temperature. While the fastest formation rates were coming from lysine and tryptophan, which took part in the reaction. And the results also showed that the growing rates of two products were in accordance with zero order in the reaction(except for lysine). |
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