Glucose loss, activation energies

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. 

Stahl and Parliment126 also determined the loss of glucose and proline with time and found that the rate constant at 200 °C for the former was about three times that of the latter (0.633 and 0.227 min-1, respectively). This difference may be partly due to regeneration of the amine and partly due to caramelisation independent of the amine. The activation energies for glucose and proline were 61.5 (14.7) and 86.7 (20.7) kJ (kcal) mol-1, respectively, and that for browning products (A at 300-304 nm) was 112.6 kJ (26.9 kcal) mol-1. 

Salicylic acid, the major metabolite of aspirin, uncouples the electron transport chain in the mitochondria. This results in (a) increased use of oxygen and production of carbon dioxide, (b) lack of ATP, and (c) excess energy no longer utilized in ATP production. The result is increased respiration and raised temperature. The alterations in respiration lead to alkalosis followed by acidosis. The lack of ATP and loss of respiratory control will cause increased metabolic activity and hypoglycemia after an initial mobilization of glucose from glycogen. 

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