Nonenzymatic browning reaction

Amino acids play a role in food processing in the development of a cooked flavor as the result of a chemical reaction called the nonenzymatic browning reaction (228). 

As part of extensive studies lasting over 30 years on the structures of chromophores involved in nonenzymatic browning reactions, two intensely orange, previously unknown, compounds have been identified (2R,8aR)-l and ZS, 8aR)-4-(2-furyl)-7-[(2-furyl)methylidene]-2-hydroxy-2//,7//,8a//-pyrano[2,3-3]pyran-3-one <1998CAR215>. Additional studies on the single Maillard reaction products of these compounds have also been reported <1998JFA3912>. 

E.-H. Ajandouz and A. Puigserver, Nonenzymatic browning reaction of essential amino acids effect of pH on caramelization and Maillard reaction kinetics, J. Agric. Food Chem., 1999, 47, 1786-1793. 

T. P. Labuza and M. Saltmarch, The nonenzymatic browning reaction as affected by water in foods, in Water Activity Influences on Food Quality, L. B. Rockland and G. F. Stewart (eds), Academic Press, New York, 1981, 605-650. 

Heterocyclic compounds are primarily formed through nonenzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the Identification of pyrazlnes, pyridlnes, thlazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The Involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions. ... 

Recent debates concerning chlorhexidine staining have considered three possible mechanisms nonenzymatic browning reactions (Maillard reactions), formation of pigmented metal sulphides of iron and tin and precipitation of dietary chromogens. 

It is interesting to note that the colour formation caused by chlorhexi-dine/black tea interaction occurs after only short exposure times and this is speculated to be at a rate much faster than nonenzymatic browning reactions at body temperature. Thus, the overall evidence indicates that the most likely mechanism of staining by chlorhexidine involves the interaction of dietary chromogens with adsorbed chlorhexidine. 

Pyrroles are common products in the reaction of different lipid oxidation products with primary amino groups of amines, amino acid, and protein (Zamora et al., 2000). For example, when squid microsomes were oxidized with iron and ascorbate, TEARS increased simultaneously with the -value (yellowness) and pyrrole compounds, concomitantly with a decrease in free amines. Off-color formation in squid muscle could be due to the nonenzymatic browning reactions occurring between aldehydic lipid oxidation products and the amines on phospholipids head groups... 

Hodge J.E. (1967) Origin of flavor in foods. Nonenzymatic browning reactions. In The Chemistry and Physiology of Flavors, 4th Symp. Oregon State University, AVI, Westport, Conn. pp. 465-491. 

The basic hve-membered iV-containing ring compounds found in tobacco whether they contain one or more nitrogens, arise from several metabolic and catabolic pathways. Additionally, many iV-containing ring compounds are formed via nonenzymatic browning reactions. 

The origins of the hve-membered V-containing ring compounds in leaf are also attributed at least partially to nonenzymatic browning or Maillard reactions between sugars and amino acids (965). Many compounds formed by nonenzymatic browning reactions have desirable havor and aroma characteristics that taken together form the characteristic bouquet and taste associated with tobacco (2337). 

It must be remembered that compounds formed by enzymatic processes can react subsequently in a nonenzymatic transformation. Additionally, by examining the chemical transformations involved in the production of compounds via nonenzymatic browning reactions, several routes can be involved in the production of the same compounds from different precursors (2337). 

Enzymatic and Nonenzymatic Browning Reactions and Control Mechanisms... 

Caramelization of sugar is another type of nonenzymatic browning reaction. These reactions are responsible for the characteristic flavors, aromas, and the brown color of many cooked foods. 

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