Maillard reaction stages

Electron-spin resonance (e.s.r.) spectra with characteristic hyperfine structure have been recorded during the initial stages of the Maillard reaction between various sugar and amino compounds. The products responsible for the spectra appear to be IV, Af -disubstituted pyrazine radical cations. The pyrazine derivatives are assumed to be formed by the bimolecular condensation of two- and three-carbon enaminol compo-... 

HPLC. Furosine and pentosidine, indicators of the initial and advanced stages of fhe Maillard reaction, respectively, increased in glucose-exposed slices (figs. 3,4 fable 3). Hydroxylysylpyridinoline apparenfly did nof form in fhe demineralized dentin at 37°C, as it did not increase in dentin exposed at 37°C (table 3). 

Fu MX, Wells-Knecht KJ, Blackledge JA, Lyons TJ, Thorpe SR and Baynes JW (1994) Kinetics, mechanisms, and inhibition of late stages of the Maillard reaction. Diabetes 43, 676-683. 

Two opposing reactions thus likely occur in caries, namely the decrease in physiological cross-links and the formation of new crosslinks in the advanced stages of the Maillard reaction. It is conceivable that the latter will prevail after a prolonged period. 

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. 

Scheme 12.2 Intermediate stages of the Maillard reaction showing the formation of carbonyl compounds...

The products in these two groups are capable of further reaction, and the subsequent stages of the Maillard reaction involve the interaction of furfurals, fu-ranones and dicarbonyls with other reactive compounds such as amines, amino acids, hydrogen sulphide, thiols, ammonia, acetaldehyde and other aldehydes. 

Namiki and Hayashi (46) recently summarized their theory of formation of intermediate free radicals, N, N -disubstituted pyrazine cation radicals, in an early stage of the Maillard reaction (cf. 47). 

Namiki, M. Hayashi, T. Formation of novel free radical products in an early stage of Maillard reaction. Prog. Food Nutr. Sci. 1981, 5, 81-91. 

The mechanism proposed by Hodge in 1953 U) for the early stages of the Maillard reaction, involving the Amadori rearrangement as a key step, has been accepted over a quarter of a century as a most apt description. Here, we propose a new mechanism... 

Development of Novel Free Radicals in the Early Stage of the Maillard Reaction... 

With the single exception of the stable free radical observed in melanoidin prepared from the glycine-glucose reaction ( 7 ) > there have been no reports of free radical formation in the early stages of the Maillard reaction. We have observed the... 

It is therefore clear that fragmentation of the sugar to two-or three-carbon products occurred readily at a very early stage in the Maillard reaction in aqueous systems. 

Formation of mainly two-carbon fragmentation products of sugars at an early stage of the Maillard reaction implies the presence of residual product(s) of the fragmentation in the reaction mixture. To demonstrate this, the reaction mixture of D-glucose with n-butylamine in ethanol was treated at the initial stage with NaBHi, and then acetylated for GLC analysis. As shown... 

Formation of novel free radical products at an early stage of the Maillard reaction was demonstrated by use of ESR spectrometry. Analyses of the hyperfine structures for various sugar-amino compound systems led to the conclusion that the radical products are N,N -disubstituted pyrazine cation radicals. These new pyrazine derivatives are assumed to be formed by bimolecular condensation of a two-carbon enaminol compound involving the amino reactant residue. The presence of such a two-carbon product in an early stage reaction mixture of sugar with amine was demonstrated by isolation and identification of glyoxal dialkylimine by use of TLC, GLC, NMR, MS and IR. 

Determination of product concentrations during the early stages of the Maillard reaction indicated a sequential reaction... 

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