Gesundheitliche bedeutung von melanoidinen

Aroma and colouring compounds in food form under the influence of heat in the course of non-enzymatic browning reactions. Different chemical reactions result in many browning products, among others the so-called melanoidines. Due to the complex and frequently high-molecular structures of the melanoidines, only a few physiologically active compounds have so far been identified and quantified in foods. Among these are pronyl lysine, first detected in bread crust, and N-methylpyridinium, whose formation is associated with the roasting degree of coffee beans. Both compounds have been found to be chemopreventively active in isolated intestinal cells, and N-methylpyridinium also in animal experiments. Pronyl lysine, furthermore, is the most effective antioxidant in bread crust. Antioxidative action of melanoidines has been shown in in-vitro-studies on roasted coffee and after consumption of espresso coffee in healthy test persons. Furthermore, it is assumed that melanoidines are capable of forming intestinal complexes of compounds detrimental to health and, thus, may reduce the exposition of the organism to potentially mutagenic or cancerogenic compounds. A prebiotic action of melanoidines is also discussed; after incubation with samples of human feces, the growth of lactobacilli and of bifidobacteria increased. These antimutagenic, anticancerogenic and prebiotic effects could so far not be related to certain structures, however. This also applies to an anticariogenic action now discussed, which so far has only been shown for melanoidines in roasted coffee. Future research should be concerned with relating the effects of chemically defined melanoidines to certain structures. Concentrations of health-promoting melanoidines in heat-treated foods could then be optimised by selection and composition of the initial products and by specific processing technologies.