Maillard reactions occurrence

The occurrence of Maillard reactions in vivo was observed for the first time only a few years ago. In 1975 we reported (3) the formation of deoxyfructoserotonin (Fig. 1) and deoxyfructolysine derivatives in the blood, in this second case poly-L-lysine being used as a model compound (Fig. 2). 

In spite of the enormous amount of work already done and the many difficulties which beset the researcher, the widespread occurrence of the Maillard reaction and the possibility of applying it to advantage301-304 justify further study of the fundamental chemical transformations which take place. 

Even though the occurrence of the Maillard reaction was recognized at the beginning of this century (1), volatile flavor compounds were not isolated and... 

The purpose of this work was to investigate the occurrence and heat-induced origin of cyclic dipeptides (DKPs) in cocoa and separately, to study the mechanism of DKP formation in simplified reaction systems. Also, the formation of volatiles vas measured in a series of model Maillard reactions of peptides, amino acid mixtures and fructose. 

During baking there is an evaporation of water from the loaf, this is particularly marked near the surface of the loaf, and this evaporation plus the occurrence of the Maillard reaction cause a characteristic dark brown crust to be formed on the exterior of the loaf. The Maillard reaction is a complex set of chemical reactions in which the amino acids in proteins react with reducing sugars such as glucose and fructose, and which are very important to our perception of flavour in baked bread. 

Cooking starch in the presence of amino acids may favour the occurrence of Maillard reactions, lowering the bioavailability of lysine in the diet. 13C CPMAS was used to follow the effect of Maillard reactions on the bioavailability of potato starch.124 A loss of crystallinity was found for the three samples studied starch, amylopectin, and amylose, being more marked for amylose. A similar study on chestnut starch indicated that Maillard reactions do not influence significantly its digestibility.125 NMR was used to characterize some Maillard reaction products extracted from model reactive mixtures such as starch-glucose-lysine 126 and lactose-lysine.127... 

An undesirable aspect of heat and alkaline treatment is that crosslinking compounds such as lysinoalanine are formed and can lead to severely impaired digestibility and reduced bioavailability of the protein. Such changes cannot be completely separated from the isopeptide formations (6), the Maillard reactions (2) and the racemization reactions (8) discussed elsewhere in this volume. In this chapter the chemistry, the analysis, the toxicology and the occurrence of lysinoalanine will be reviewed. 

It should be mentioned that today the medical field has become the major discipline researching the Maillard reaction since it plays a role in aging as well as several diseases. The dominance of the medical discipline at the last few international symposia on the Maillard reaction illustrates this occurrence [6-9]. 

About 10 years ago iV-(l-methyl-4-hydroxy-3-imidazolin-2,2-ylidene)alanine was isolated from beef broth and reported to impart a brothy, thick sour taste as characteristic taste impression of beef bouillon (7). Although this compounds has been suggested to be formed from the reaction between creatinine and lactic acid, neither the formation pathways, nor the human threshold concentration for the sensory activity of that molecule was yet confirmed. In order to answer the question as to whether this taste modulator might be formed by Maillard-type reactions of creatinine, the objective of the present investigation was to screen for taste modulating creatinine glycation products in heated creatinine/ribose solutions and to investigate the sensory activity of these derivatives. Furthermore, LC-MS/MS studies should be performed to verify the natural occurrence of the identified taste modulators in beef stock. 

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