Kinetics of the Maillard Reaction

The kinetics of the early-stage Maillard reaction has been considered by Ge and Lee.117 Their basic equation was as follows  

Colour formation, which lies well beyond the early-stage Maillard reaction, has been described by Wedzicha and Leong118 by the following scheme (DH = deoxy-hexosone)  

Mundt el al.n9 have adapted the above scheme for the maltose-glycine system (pH 5.5, 70 °C). Multiresponse modelling gave excellent fits for the time course of the concentrations of glucose, melanoidins (A470, number of maltose molecules incorporated from U-14C-labelled maltose), 3-DH (as quinoxaline derivative), maltose, and SIV (in maltose-glycine-SIV systems). 

Martins and van Boekel120 have considered the key intermediates in the early stages of the above scheme, which they modified to 

AS is a reactive intermediate, formed from the amino acid (A) and sugar (S) prior to the Amadori product (ARP). Its nature, say, Schiff base or glucosylamine/enaminol, was not studied. However, its inclusion was of major importance in obtaining fits by multiresponse modelling of the decomposition of fructosylglycine on its own (pH 5.5, 100 °C), when glycine and 1- and 3-deoxyosones (DG) were the only products detected. Because of the reactivity of DGs, further products were expected, hence the inclusion of k3. 

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Piergiovanni, L., de Noni, I., Fava, P., and Schiraldi, A. (1989). Nonenzymatic browning in processed cheeses. Kinetics of the Maillard reaction during processing and storage. Ital. J. Food Sci. 1,11-20. 

Reaction Kinetics. Data on the kinetics of the Maillard reaction are not extensive. It is well known that cooking food under different conditions can result in a variety of fiavors. 

Fu MX, Wells-Knecht KJ, Blackledge JA, Lyons TJ, Thorpe SR and Baynes JW (1994) Kinetics, mechanisms, and inhibition of late stages of the Maillard reaction. Diabetes 43, 676-683. 

The results discussed in this article showed that the effect of inorganic phosphate on the course of the Maillard reaction may be described by general base catalysis following approximately first-order kinetics. The effect is optimum in the pH-range between 5 and... 

Knowledge of the Maillard reaction is being extended very actively in many different ways. The participation of free radicals has already been dealt with in Chapter 2 and work on colour and flavour aspects is being deferred to Chapters 4 and 5, respectively. This chapter deals with a number of relatively disparate topics, namely, the effects of pH, high pressure, 7g, and the use as reactants of amines other than amino acids, of lipids, and of oligo- and polysaccharides, as well as the determination of a-dicarbonyl intermediates, control of aldol/retroaldol reactions, fluorescence, kinetic aspects, and sites of protein glycation. 

The Amadori product from D-glucose 33 and L-proline decomposes at 130 °C in DMF to afford 33 and D-Mannose 54, indicating the reversibility of the Amadori reaction. A kinetic study using 33 and phenylalanine indicates that the Schiff s base formation is the rate-determining step of the Maillard reaction [275,276]. 

In our investigation on the effect of Maillard reaction products on the absorption of tryptophan (36), the kinetics of the absorption of tryptophan in the presence of Maillard reaction products formed in the glucose-tryptophan system was studied by bott vitro everted gut sac method and vivo catherization of the portal vein. Fructose-L-tryptophan (Amadori compound) appeared to be the major fraction of the reaction products when fractionated using a cellulose column eluted by water-saturated n-butanol. The absorption of L-tryptophan was partially inhibited vitro and vivo by fructose-L-tryptophan in a competitive manner with an inhibitor constant (Ki) of l.lmM. The relative absorption rate of L-tryptophan was significantly lower in the presence of the Maillard reaction products than in the presence of fructose-L-tryptophan indicating the presence of other inhibitory factors in the reaction products. The in vivo absorption of fructose-L-tryptophan was almost negligible compared to that of tryptophan. The inhibited absorption by Maillard reaction products, may have contributed in part to an incomplete recovery in the growth of the rats when fed a supplemented browned synthetic amino acid diet. 

Strecker aldehydes are quantitatively the major products of the Maillard reaction. In addition to their intrinsic flavor, they are very reactive and participate in numerous reactions that make additional contributions to flavor development in foods. There is a lack of information on the reaction kinetics of these Strecker aldehydes as well as other flavor compounds. Thus a kinetic study on the formation of methional and two secondary products (dimethyl disulfide and 2-acetylthiophene) from the reaction of amino acids (0.075 mole) and glucose (0.5 mole) in aqueous model systems was conducted. Systems were heated at temperatures from 75 to 115°C at times from 5 min. to 7.5 h and pH s of 6, 7, and 8. Kinetic data are presented and discussed. 

High temperature short time kinetics of a Maillard reaction in a proline/gjucose model system were recently investigated by Stahl and Parliment at temperatures ranging between 160 C and 220°C and reaction times ranging between 0.25 min and 5 min. It was found that one compound, 5-acetyl-2,3-dihydro-l(H)-pyrrolizine, was the major product and formed by pseudo zero order Idnetics. It was determined that this compound had a relatively high energy of activation of 45 Kcal/mole (22). 

Extensive reports of the Maillard reaction can be found in the scientific literature, most focus on aqueous systems, and few monitor the reaction with time. An interesting system for processing liquid streams of reactants under precise time-temperature conditions was described by Stahl and Parliment [1]. Analysis of the data resulted in a plot of flavor and color generation with time from which the kinetics of the reactions could be easily calculated. Gaining the same sort of data from food matrices that dehydrate on heating is more difficult, and there are few published reports. 

The formation of brown pigments via the Maillard reaction, especially in model systems (e.g. glucose-glycine), usually follows zero-order kinetics, but the loss of reactants has been found to follow first- or second-order kinetics in foods and model systems. Activation energies of 109, 116 and 139 kJ mol-1 have been reported for the degradation of lysine, the formation of brown pigments and the production of hydroxymethylfurfural (HMF), respectively. 

These two aspects of such a complex change as the Maillard reaction are considered together, because most of the kinetic studies are based on certain assumptions regarding the mechanism of reaction. It is convenient to consider first the reaction in acid medium, and then the reaction at pH values of about 6.5 and above. 

Jousse et al.130 have surveyed the data available on the kinetics of aroma formation by the Maillard reaction and have assembled a simplified, but broadly based, kinetic scheme, as outlined in Scheme 3.3. 

F. Jousse, T. Jongen, W. Agterof, S. Russell, and P. Braat, Simplified kinetic scheme of flavor formation by the Maillard reaction, J. Food Sci., 2002, 67, 2534-2542. 

Martins, S.I.F.S. and van Boekel, M.A.J.S. Kinetics of the glucose/glycine Maillard reaction pathways Influences of pH and reactant initial concentrations. Food Chem., 92,437, 2005. 

Wedzicha, B.L. and Vakalis N. Kinetics of the sulphite-inhibited Maillard reaction The effect of sulphite... 

The mechanism of the entry of fructose into the Maillard reaction (a series of sugar/amino acid processes in vivo) has been studied by DFT the order of reactivity for the isomers is predicted as a- > /3- > open-chain. Heyns rearrangement products are most favourable under basic conditions, possible under neutral conditions, but unfeasible at or below glycine s isoelectric point. Kinetic and activation parameters have been reported for the corresponding glucose/proline reaction. ... 

Kinetics of the Formation of Methional, Dimethyl Disulfide, and 2-Acetylthiophene via the Maillard Reaction... 

These results were consistent with the earlier work of Warbier et al. (20) and Labuza et al. (21) who found that formation of browning products in the Maillard reaction gener ly followed pseudo zero order kinetics when reactant concentrations were in excess. 

There is very little work published on the kinetics of aroma formation via the Maillard reaction. However, what work has been done has indicated that volatile formation is very sensitive to both compositional and processing changes. One can generate kinetic data for volatile formation in a simple model system, include another precursor that should have no direct effect on the kinetics of interest, and find major changes in reaction kinetics. 

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