Maillard model systems, aqueous

S. M. Monti, R. G. Bailey, and J. M. Ames, The influence of pH on the non-volatile reaction products of aqueous Maillard model systems by HPLC with diode array detection, Food Chem., 1998, 62, 369-375. 

Analysis of NonvolatUe Reaction Products of Aqueous Maillard Model Systems The Effect of Time on the Profile of Reaction Products... 

The work described here is part of a continuing project aimed at investigating the formation of non-volatile compounds, both colorless and colored, in Maillard model systems (P, 10). The focus of this report is the effect of time of heating and subsequent storage on the profile of reaction products formed from an aqueous xylose-lysine hydrochloride model system. 

In heated foods the main reactions by which flavors are formed are the Maillard reaction and the thermal degradation of lipids. These reactions follow complex pathways and produce reactive intermediates, both volatile and non-volatile. It has been demonstrated that lipids, in particular structural phospholipids, are essential for the characteristic flavor development in cooked meat and that the interaction of lipids with products of the Maillard reaction is an important route to flavor. When model systems containing amino acids and ribose were heated in aqueous buffer, the addition of phospholipids had a significant effect on the aroma and on the volatile products. In addition a number of heterocyclic compounds derived from lipid - Maillard interactions were found. The extent of the interaction depends on the lipid structure, with phospholipids reacting much more readily than triglycerides. 

Much attention has recently been paid to arginine as a melanoidin precursor. In a model system, lV -acetylarginine was first allowed to react with glyoxal in aqueous solution at pH 7, followed by furfural. Repeated chromatography of the aqueous residue after ethyl acetate extraction led to a 1% yield of the deep red 29.180 Such a compound provides an example of a potentially coloured crosslink in proteins derived by the Maillard reaction (see Chapter 8). 

S.-J. Ge and T.-C. Lee, Kinetic significance of the Schiff base reversion in the early-stage Maillard reaction of a phenylalanine-glucose aqueous model system,. /. Agric. Food Chem., 1997, 45, 1619-1623. 

Strecker aldehydes are quantitatively the major products of the Maillard reaction. In addition to their intrinsic flavor, they are very reactive and participate in numerous reactions that make additional contributions to flavor development in foods. There is a lack of information on the reaction kinetics of these Strecker aldehydes as well as other flavor compounds. Thus a kinetic study on the formation of methional and two secondary products (dimethyl disulfide and 2-acetylthiophene) from the reaction of amino acids (0.075 mole) and glucose (0.5 mole) in aqueous model systems was conducted. Systems were heated at temperatures from 75 to 115°C at times from 5 min. to 7.5 h and pH s of 6, 7, and 8. Kinetic data are presented and discussed. 

Structures 4.1 show some low-molecular-mass coloured compounds formed in model Maillard systems. The organic chemistry underlying colour in melanoidins was not clear until 1972, when a specific compound, 4a, was isolated by Severin and Kronig167 in 0.07% yield from a heated aqueous mixture of xylose and isopropylamine acetate. It is yellow with Alliax = 365 nm. When the amine was replaced by glycine or lysine, the yield dropped further. Similar results were obtained when ara-binose was substituted for xylose. Subsequent work led to the identification of related compounds (see 4b and 4c), in some of which the ring oxygen of the furfural is replaced by NR. 

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