Pronyl-lysine

M. Lindenmeier, V. Faist, and T. Hofmann, Structural and functional characterization of pronyl-lysine, a novel protein modification in bread crust melanoidins showing in vitro antioxidative and Phase Eli enzyme modulating activity, J. Agric. Food Chem., 2002, 50, 6997-7006. 

A French stick is mainly crust, and in France it is common practice to ignore the softer inner part, and maybe that s how all bread should be eaten because the healthiest part of bread is the crust, at least according to Thomas Hofmann of the University of Munster. He reported in 2002 that crusts contains an antioxidant, pronyl-lysine. This forms from starch and the amino acid lysine when bread is baked, and it forms near the surface of the loaf, not in the soft interior. For pronyl-lysine to form the temperature has greatly to exceed 100 °C, which it does on the outside... 

The chemical principle behind the antioxidant properties of Maillard reaction products is currently not well understood. It is assumed that these properties show both low molecular weight products and high molecular weight melanoidins. As the structure of melanoidins has not been clarified satisfactorily, it is difficult to explain the chemical nature of their antioxidant activity. The active structures are probably reductones and aminoreductones, bound in melanoidin molecules that reduce the products of autoxidation. One of a few identified reductone structures in real food melanoidins is 2,4-dihydroxy-2,5-dimethyl-l-(5-acetamino-5-methoxycarbonylpentyl)-3-oxo-2H-pyrrole bound by a peptide bond. This so-called pronyl-L-lysine (pyrrolinone... 

Figure 4.101 Formation of bound pronyl-L-lysine in bread crust.

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