Maillard reaction formation rate

The most obvious characteristic is, of course, the formation of a yellow or brown coloration. This becomes progressively darker with time, until it is dark-brown or even black,97 -103 -104 but, if the first step in the Maillard reaction is the formation of the glycosylamine7 - 105 (which is usually colorless48), it is obvious that the rate of color formation alone is not a safe... 

Lipid-Protein-Carbohydrate Interactions. Evidence for such complex interaction was recently reported by Huang et al (36) who observed that the addition of corn lipids to zein and corn carbohydrates enhanced the formation of alkylpyrazines, indicating that lipid-derived free radicals may accelerate the rate of Maillard reactions. Two of the alkylpyrazines, identified in such mixtures after heating for 30 minutes at 180°C, have 5-carbon alkyl substitution at the pyrazine ring and could only be explained by interaction of lipid or lipid decomposition products. These authors suggested that condensation of amino ketones, formed by protein-carbohydrate interaction, may yield 3,6-dihydropyrazine which would in turn react with pentanal, a lipid oxidation product, to form 2,5-dimethyl-3-pentylpyrazine. 

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]. 

FIGURE 4.6 Dependence of (pseudo) first-order reaction rate constants (k) on temperature (T). Approximate examples for heat inactivation of alkaline phosphatase and plasmin, for killing of Clostridium botulinum spores, and for the formation of a certain small amount of Maillard products. t 0A is the time needed for the reaction to proceed for 0.1 times the final value (not for the Maillard reaction). 

Leahy and Reineccius [22] found the influence of water activity on the rate of formation of alkyl pyrazines in a model system to parallel that of classical Maillard reaction. Briefly, the accumulation of pyrazines reached a maximum when heated at an Aw of ca. 0.75 and decreased with either increasing or deCTeasing Aw. This observation suggests that the rate of pyrazine formation is controlled by the initial stages of the Maillard reaction as opposed to an effect on specific pathways of pyrazine formation. 

Leahy [15] studied the influence of Aw and pH on the formation of pyrazines. She found that pyrazine formation increased linearly with increasing Aw up to an Aw of about 0.75 and then either dcCTeased or was unchanged at an Aw of 0.84, depending upon the pyrazine. A maximum in reaction rate at an Aw around 0.75 is consistent with Maillard browning as measmed by the consumption of reactants or the formation of pigments. Leahy [15] reported that pyrazine formation rate increased by an average of 1.37-fold for each iuCTease in Aw of 0.1 units. Similarly, a linear relationship was found between the rate of pyrazine and 2-methylpyiazine formation and pH (within the range of pH 5-9). 

The kinetics of the reaction between D-glucose and several alkylamines have been examined by a potentiometric method, and the rate of formation of iV-glyco-sides [e.g. l-JV-(4-aminobenzoyl)-D-xylopyranosylamine] has been measured by determining the decrease of free amino-groups using l,2-naphthoquinone-4-sulphonic acid. Rate constants for the Maillard reaction of glycine with D-xylose, D-glucose, and D-fructose have also been reported. ... 

The rate of fat oxidation in foods depends greatly on water activity (see Section 7.9). In dry foods, oxygen can more easily penetrate into the material than in normal foods. The minimum rate of oxidation occurs in foods with water activity values around 0.3. This situation is explained by the decrease in catalytic activity of metals, by quenching free radicals and by formation of antioxidants in the Maillard reaction. In foods with higher water activity, the rate of oxidation is again higher, probably due to increased mobility of metal ions, which catalyse the autoxidation. 

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