Fractional Composition of Melanoidin Pigment

Abstract

Melanoidin complex formed as a result of interaction between protein amino acids and sugars consists not only of high-molecular compounds, but its important colored part is relatively low-molecular. Based on the example of interaction between glycine labeled preparations and D-glucose, we set a goal of study the regularities of glycine carbon atoms inclusion into melanoidin polymers. Carbon atoms of amino acid carboxyl group are quite actively included into melanoidin pigment composition and presumably, this occurs by means of products formed resulting from Amadori rearrangement. In this regard, interesting results have been obtained resulting from study of polymeric products of Maillard reaction going between D-glucose and 1-alanine. Results of element analysis of polymers obtained by us (>3500 Daltons) show that CN ratio, as one of the main parameters of these polymers, is smaller for products formed at pH8,0, than those formed at pH 5,8. Such regularity, when CN ratio of melanoidin polymers decreases with increase of pH, is described for products of alanine and glucose interactions. At that, resulting from autoradiographic analysis of acidic hydrolysates of the mentioned melanoidin polymers, there was no free radioactive glycine found in these hydrolysates. Thus, glycine is included into polymer composition not in the form of united molecular chain, but as a molecule fragment. Based on these data one may conclude that roughly 65% of methylene carbon and approx. 14% of carboxyl carbon of glycine molecule are incorporated into melanoidin polymers under conditions we have studied. The melanoidin polymer obtained at 100°C temperature and pH 5,8 reacts with glycine at pH 8.0, the melanoidin polymer obtained at 80°C temperature reacts with glycine at 100°C temperature etc. The degree of glycine labeled carbon’s inclusion into melanoidin is more highly influenced by pH change than by temperature rise.