Generation from Maillard reaction

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. 

Chun H.K. and Ho C.T. (1997) Volatile N-containing compounds generated from Maillard reactions under simulated deep-fat frying conditions. J. Food Lipids 4 (4), 239—44. 

C.-T. Ho and J. Chen, Generation of volatile compounds from Maillard reaction of serine, threonine, and glutamine with monosaccharides, in Flavor Chemistry Thirty Years of Progress, R. Teranishi, E. L. Wick, and I. Homstein (eds), Kluwer/Plenum, New York, 1999, 327-333. 

As well as the amino and carboxy groups, the amino-acid side-chain is also involved early in the Maillard reaction, so the side-chain functional groups become incorporated into the products from Maillard reactions. Cysteine, in particular, reacts with glucose to generate numerous reaction products, some of which introduce attractive tastes and aromas to foods associated with sulphur functional groups. 

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. 

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.

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). 

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. 

Tressl et al7r J1 designated the linear polymers as Type I and the branched ones as Type II. In most melanoidins, they would represent domains (or substructures), unsubstituted pyrroles and Strecker aldehydes, for example, being integrated into the melanoidin backbone, giving a complex macromolecular structure overall. Tressl et aV1 consider the oligomerisation/polycondensation reactions described as the only experimentally established pathways by which simple Maillard products generated from hexoses and pentoses are easily and irreversibly converted into macromolecules. 

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. 

A. Amoldi and G. Boschin, Flavors from the reaction of lysine and cysteine with glucose in the presence of lipids, 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, 240-250. 

The polymeric material from the plain caramel is generated from the condensation reactions of the aldehydes and ketones formed by heating the sugar with bases or acids. The ammonia caramel is formed in a Maillard type reaction [2] where carbonyl compounds react with amino groups or ammonia. This type of compound will be further presented in Sections 11.2 and 11.3. Sulfite caramel is also a Maillard type polymer. However, as hydrogen sulfites form stable adducts with aldehydes and ketones, the sulfite caramels include in their structure sulfite groups. 

In this reaction, creatine generates creatinine that reacts with a pyridine or a pyrazine (formed from the Maillard reaction) and an amino acid (glycine, alanine, etc.) to form the heterocyclic amine. 

In proteinaceous foods rich in saccharides or secondary lipid oxidation products, the Maillard reaction prevails. The generation of pyrraline from Lys can be used as an indicator of thermal changes in proteins ... 

Izzo, H.V., Yu, T.-H., and Ho, C.-T., Flavor generation from the Maillard reaction of peptides and proteins, in Progress in Flavor Precursor Studies, Schreier, P. and Winterhalter, P., Eds., Allured Publishing Corp., Carol Stream, IL, 1992, p. 315. 

The Maillard reaction between reducing carbohydrates and amines is among the most important flavor generating reactions in thermally processed foods (5). Thus, it might be expected that in foods treated with HHP, but at low temperatures, some of the typical aroma compounds might not be formed. Only two studies about the influence of HHP on the formation of volatiles in Maillard model systems are currently available (6, 7). Bristow and Isaacs (d) reported that at 100°C, the formation of volatiles from xylose/lysine was generally suppressed when HHP was applied. Hill et al. (7) confirmed this observation for a glucose/lysine system. However, it has to be pointed out that the samples analyzed were not reacted in a buffered system and, also, the reaction time of the pressure-treated and untreated sample were not identical. 

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