[Mutagenic substances in amino acid and protein pyrolysates and in heat-treated food]

[The effect of Maillard reaction products on enzyme reactions]

In this article current knowledge about the Maillard reaction in vivo is described first, especially the glycosylation reactions of various tissues and the identification of different final products and intermediates of Maillard reaction. The influence of MRP on digestion is of significant importance. These products are absorbed in different ways and are excreted in various amounts. Hence, the organism is variably influenced by MRP. The influence of defined MRP, of glycosylated proteins and of melanoidins on glycosidases and proteases is described. The effects produced depend on the enzyme and on the used MRP. Reactive alpha-dicarbonyl compounds play an important role in the organism. Further possible reactions of these compounds caused by reductases are discussed. The protein structure of enzymes is changed by Maillard reaction. Thereby the enzyme activity is influenced by covalent modifications of different amino acids and by inter- and intramolecular crosslinking. Finally, the use of enzymes and monoclonal antibodies for detection of MRP is discussed.

[Formation of IQ-compounds in meat and meat products]

During meat processing mutagenic imidazoquinolines and imidazoquinoxalines ("IQ-compounds") may be formed by Maillard reaction of reducing sugars, amino acids, and creatine/creatinine. IQ-compounds isolated from low-moisture model systems and meat extract by liquid-liquid-distribution were fractionated on a cation exchanger and separated on an RP phase. After acetylation the separated compounds were identified by gas chromatography/mass spectrometry based on their characteristic mass fragment ions. During heating the model systems at 100 degrees C the formation of IQ-compounds begins and greatly increases by further raising the temperature. In different amounts IQ-compounds could also be detected in commercially available meat extracts.

[The decomposition of reducing sugars and amines in the Maillard reaction]

Through the Maillard reaction, occurring in food and in the human body, reducing sugars, amino acids and proteins are transformed. Some general and also specific degradation pathways for pentoses, mono- and disaccharides can be defined. The structures of the products are influenced by the type of amine (primary or secondary). During the degradation reactions C-C fissions of the sugars and amino acids (Strecker degradation) can be observed. Some Maillard products are suited as indicator substances to determine the extent of the Maillard reaction.

[The subacute toxicity of glucosylthiazolidine-4-carbonic acid in rats]

Glucosylthiazolidine-4-carbonic acid, an intermediate of the Maillard reaction between D-glucose and L-cysteine, was given in doses of 0, 25, 50 or 100 mg/kg b.w. by oral intubation to male and female rats for 21 days. General appearance, growth, food consumption, haematology, urine analysis and serum chemistry including determinations of enzyme activities, organ weights and macroscopic and microscopic pathology were used as criteria for adverse effects. Effects on the kidneys were indicated by oliguria and decreased specific gravity of the urine in males and histopathological changes of the proximal tubules in females. The no-effect dose established from this study is 25 mg/kg b.w.