Melanoidin formation

The kinetics of the Amadori-compound formation from D-glucose and l-lysine, as well as melanoidin formation, has been examined. The so-called Amadori compounds are formed at an exponential rate, while showing pseudo-first-order disappearance of L-lysine in the presence of... 

An effort has also been made to determine the structure of products providing coloration in the Maillard reaction prior to melanoidin formation. The reaction between D-xylose and isopropylamine in dilute acetic acid produced 2-(2-furfurylidene)-4-hydroxy-5-methyl-3(2/f)-furanone (116). This highly chromophoric product can be produced by the combination of 2-furaldehyde and 4-hydroxy-5-methyl-3(2//)-furanone (111) in an aqueous solution containing isopropylammonium acetate. The reaction between o-xylose and glycine at pH 6, under reflux conditions, also pro-duces " 116. Other chromophoric analogs may be present, including 117,... 

Dreizen S, Gilley EJ, Mosny JJ and Spies TD (1957) Experimental observations on melanoidin formation in human carious teeth. J Dent Res 36, 233-236. 

Sattler, L. Zerban, F. W. Unfermentable reducing substances in molasses — volatile decomposition products of sugars and their role in melanoidin formation. Ind. Eng. Chem. 1949, 41, 1401-6. 

Fig. 4.—Dependence of Color Intensity of a D-Glucose-Glycine Solution on pH. (Curve A intensity of total color curve B intensity of color due to non-melanoidin products curve C color from melanoidin formation, by difference between A and B.164)...

Blue-Mi showed some resemblance to a melanoidin prepared from xylose and n-butylamine neutralized with acetic acid in methanol at 50 °C for 7 d, based on sugar moiety per N, residual OH content, periodate consumption, dehydration ratio, and dehydrogenation ratio. This led Kato and Hayase to suggest Blue-Mi as a key intermediate in melanoidin formation. 

T. Hofmann, W. Bors, and K. Stettmaier, Radical-assisted melanoidin formation during thermal processing of foods as well as under physiological conditions, J. Agric. Food Chem., 1999, 47, 391-396. 

The browning reaction involves a number of steps. An outline of the total pathway of melanoidin formation has been given by Hodge (1953) and is shown in Figure 3-7. According to Hurst (1972), the following five steps are involved in the process ... 

The principal degradation mechanism of organic matter in the formation of peats (humic substances included) and leading to the formation of coal, therefore, appears to involve the preferential breakdown of labile biomolecules (carbohydrates, etc.), and the selective preservation of inert and relatively inert (i.e., somewhat degraded) biomolecules (Hatcher and Clifford, 1997). Melanoidin formation may also play some role in the... 

Young D. K., Sprang S. R., and Yen T. E. (1977) Preliminary investigation on the precursors of the organic components in sediments-melanoidin formations. In Chemistry of Marine Sediments (ed. T. E. Yen). Ann Arbor Science,... 

Fig. 4.1 Reactions and structures involved in melanoidin formation (a) example of sugar rearrangement (b) typical units in the carbohydrate backbone of melanoidin (c) common initial condensation reaction between a sugar residue and an amino acid (after Rubinsztain et al. 1984).

YAYLAYAN, V. A. and KAMINSKY, E. (1998). Isolation and structural analysis of Maillard polymers caramel and melanoidin formation in glycine/glucose model system. Food Chemistry, 63, 25-31. 

CROSSPY A Radical Intermediate of Melanoidin Formation in Roasted Coffee... 

Although extensive investigations have been perfohned for more than 35 years, the chemical nature and the formation of the free radical in roasted coffee is still unknown. The objective of the present investigation was, therefore, (i) to characterize the chemical structure of the free radical formed during roasting of coffee beans, and (ii) to study whether this radical is somehow involved in melanoidin formation. 

Hie radical cation CROSSPY was identified as a previously unknown type of cross-linking amino acid involved in melanoidin formation during roasting of coffee beans. Also for other browned foods such as wheat bread crust or roasted meat a tight relationship between the formation of CROSSPY and browning development could be observed (Hofinann, unpublished results), thus. 

The second method of melanoidin formation, which also leads to protein oligomers, is more typical for foods. This reaction assumes covalent bond formation of transformation products of sugars on the side chains of proteins, especially of bound lysine, arginine or cysteine, to form chromophore structures. Some of the previously mentioned AGE structures, such as pentosidine (4-241) are coloured. Other chromophores include substances that are formed in systems containing furan-2-carbaldehyde. The lysyl residue in a peptide chain reacts in a neutral solution with furan-2-carbaldehyde, forming chromophore (4-253). Also described are... 

FIGURE 14 Simplified scheme of melanoidin formation by the sugar-amine reaction ( means presence or absence). 

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