Melanoidins
As melanoidins (of gr. Μέλας "black") yellow-brown to almost black colored, nitrogen-containing organic compounds which the food produced in many by heating as coffee , bread and beer are included.
Production and occurrence
The melanoidins arise as by-products in the browning reactions of amino acids and reducing sugars in the so-called Maillard reaction . The carbonyl group of the sugar reacts with the amino group of the amino acid or protein molecule and nitrogen-substituted glycosylamines and water are formed. High temperatures promote the formation of melanoidins, which are contained in many foods such as roasted coffee beans (up to approx. 30%), bread (here especially in the browned crust) and beer (made from the malt ). These substances partly determine the sensory quality such as color, smell and taste of the food.
Properties and biological effect
All melanoidins are glycosylamines; H. Condensation products from a monosaccharide and an amine . Relatively little is known about their exact structure and chemical structure, but new knowledge is constantly being gained at various universities. One of the few defined melanoidins is pronyl-lysine , the structure of which was clarified in 2002. The substance group of the melanoidins consists of low molecular weight representatives with masses below 1,000 Daltons , which are derived from individual amino acids, and polymers with masses over 100,000 Daltons, which arise from proteins. The fabrics are usually colored in an intense light brown to black.
At the moment, the main focus is on discussions about the positive and negative effects of melanoidins. One of the positive effects is its antioxidant effect. Pronyl-lysine is even allowed to inhibit the development of cancer . Melanoidins also absorb potentially dangerous substances from food, such as B. heavy metal ions or cholesterol . One of the negative effects is the absorption of trace elements , which are thus withdrawn from the organism.
Individual evidence
- ^ Institute for Food Chemistry at the University of Münster : Formation, properties and structure of melanoidins
- ↑ Technical University of Berlin : The brown secret of coffee & Co. , November 2001
- ↑ M. Lindenmeier, V. Faist, T. Hofmann: Structural and functional characterization of pronyl-lysine, a novel protein modification in bread crust melanoidins showing in vitro antioxidative and phase I / II enzyme modulating activity. In: Journal of agricultural and food chemistry. Volume 50, Number 24, November 2002, pp. 6997-7006, PMID 12428950 .
- ↑ medicine-aspekte.de: Bread crust - healthier than its reputation: Effects of high molecular weight roasted products ( Memento from January 10, 2012 in the Internet Archive ), August 29, 2004 (version from the archive.org Internet archive of January 10, 2012).