Generation, Maillard reactions

Table V shows thermally generated Maillard reaction products with medium and low volatility isolated from the tomato products by extraction with methylene chloride and cleaned up by gel chromatography. They were separated on a 60 m fused silica capillary (conditions as for the volatile compounds listed in Table IV).

The generation of artifacts has also been an intermittent concern. Hayashi et al.59 reported a heat-induced artifact for conversion of Amadori products of the Maillard reaction to V -(carboxymcthyl) lysine that had the potential to affect IHC staining. However, among thousands of articles pertaining to... 

The Maillard reaction is inextricably linked to the desirable flavour and colour characteristics of cooked foods and this review provides an insight into some of the chemistry associated with flavour generation in the reaction and the different aromas which are involved. The chemical pathways associated with the initial and intermediate stages of the Maillard reaction are presented and routes by which the important classes of aroma compounds may be formed from Maillard intermediates are discussed. 

Mauron J (1981) In Eriksson C (ed) Maillard Reactions in Food. Pergamon, Oxford, p 3 Mottram DS (1994) In Parliment TH, Morello M), McGorrin R) (eds) Thermally Generated Flavors Maillard, Microwave, and Extrusion Processes. ACS Symposium Series 543. American Chemical Society Washington, p 104 Nursten HE (1980) Food Chem. 6 263... 

Since process flavours are generated by the interaction of raw materials like protein derivatives (amino acids) and reducing sugars (Maillard reaction), it is obvious that a large number of prepared food products are affected ... 

Figure 2.9. Glucose can enolize and reduce transition metals thereby generating superoxide free radicals (02" ), hydroxyl radicals ( OH), hydrogen peroxide (H202) and reactive dicarbonyl compounds. Adapted with permission from Wolff, S. P. (1996). Free radicals and glycation theory. In The Maillard Reaction. Consequences for the Chemical and Life Sciences, Ikan, R., ed., John Wiley Sons, Chichester, UK, 73-88.

The reaction pathways for the Maillard Reactions have been studied and reviewed by many researchers since Dr. Maillard s early work (4—6) These papers give a concise outline of the major chemical pathways identified in the Maillard Reaction Mechanism. In heat treated meat with nearly 75% of those volatiles generated are pyrazines derivatives (7). Those pyrazines have been found to play an important role in developing a roasted flavor in heated products. They will be discussed later. 

In addition to simple model systems, more complex systems which are closer to actual foodstuffs have been used to investigate the formation of flavor chemicals in the Maillard reaction. Sixty-three volatile chemicals were isolated and identified from starch heated with glycine (4). When beef fat was used as a carbonyl compound precursor in a Maillard model system with glycine, 143 volatile chemicals were identified (6). These included fifteen n-alkanes, twelve n-alkenes, thirteen n-aldehydes, thirteen 2-ketones, twelve n-alcohols, and eleven n-alkylcyclohexanes. Recently, the effect of lipids and carbohydrates on the thermal generation of volatiles from commercial zein was studied (7). 

The Maillard reaction commonly occurs in food products and during food processing. A typical or pure Maillard reaction is simply the reaction of a sugar and an amino acid. Strictly speaking, the sugar must be a reducing carbohydrate and the amino acid can be either free or bound, as a peptide or protein. The reaction generates not only volatile compounds, which provide odor, but also odorless nonvolatile compounds, some of which are colored. 

The thermal reaction of cystine and 2,3-dimethyl-4-hydroxy-3 (2H)-furanone (DMHF), a modified Maillard reaction is important for the generation of meat flavors. The reaction products, their flavor compounds, aroma character and yield vary, according to the reaction parameters. These parameters include the reaction medium, duration, water content, temperature, pH and presence or absence of oxygen. 

There is increasing evidence that the interaction of lipids with the Maillard reaction is relevant to the generation of flavor in many cooked foods. For instance, the removal of lipids from coconut has been shown to cause flavor changes in the roast material (12). Uncooked coconut contained significant amounts of lactones as the main aroma components on roasting pyrazines, pyrroles and furans were also found in the aroma volatiles which added a strong nut-like aroma to the sweet aroma of the unroasted coconut. When ground coconut was defatted and then roasted, the sweet aroma due to lactones disappeared and the product possessed a burnt, nut-like aroma. A marked increase in the number and amount of Maillard reaction products, in particular pyrazines, was found. 

Volatile compounds generated by model systems of zeln, corn amylopectin and corn oil extruded at barrel temepratures of 120°C and 165°C were analyzed by GC and GC/MS. The largest quantities of lipid oxidation products were detected in systems containing all three components. In each system, the quantity of 2,4-deca-dienal was low relative to the quantities of hexanal, heptanal and benzaldehyde. Identification of the Maillard reaction products, 2-methyl-3(or 6)-pentyl-pyrazine, 2-methyl-3(or 6)-hexylpyrazine and 2,5-di-methyl-3-pentylpyrazine, suggested that lipid-derived aldehydes might be involved in the formation of substituted pyrazines. 4-Methylthiazole was identified as a major decomposition product of thiamin when corn meal containing 0.5% thiamin was extruded at a final temperature of 180°C. 

Y. Chen and C.-T. Ho, Effects of camosine on volatile generation from Maillard reaction of ribose and cysteine, J. Agric. Food Chem., 2002, 50, 2372-2378. 

D. S. Mottram, Flavor compounds formed during the Maillard reaction, in Thermally Generated Flavors Maillard, Microwave, and Extrusion Processes, T. H. Parliment, M. J. Morello, and R. J. McGorrin (eds), American Chemical Society, Washington, DC, 1994, 104-126. 

T. Hofmann, Studies on melanoidin-type colourants generated from the Maillard reaction of casein and furan-2-carboxaldehyde — chemical characterisation of a red coloured domaine, Z. Lebensm. Unters. Forsch, 1998, 206, 251-258. 

T. H. Parliment, A concerted procedure for the generation, concentration, fractionation, and sensory evaluation of Maillard reaction products, in Flavor Chemistry Thirty Years of Progress, R. Teranishi, E. L. Wick, and I. Homstein (eds), Kluwer/Plenum, New York, 1999, 43-54. 

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