Maillard browning degradation

Sulfur Compounds of Beef Flavor. Methional, which results from the degradation of methionine, is an important contributor to flavor in meat. Thiolanes, formed during the cooking of beef, have peculiar oniony flavors that also augment the quality of the meaty flavor. Thiophenes and thiofurans are also important to meaty flavors. Sulfides, such as methyl sulfide, are oxidized to methyl sulfoxide and methyl sulfone. Condensation reactions of Maillard browning products also result in thiazoles such as benzothiazole, an important component of meat flavor. 

Biochemical Degradation Biochemical degradation is another harmful transformation that occurs with most biological products. There are four key reactions to consider lipid oxidation, Maillard browning, protein denaturation, and various enzyme reactions. These reactions are both heat- and moisture-dependent such that control of temperature and moisture profiles can be very important during drying. 

Brown proposed a mechanism where the enolate radical resulting from the radical addition reacts with the trialkylborane to give a boron enolate and a new alkyl radical that can propagate the chain (Scheme 24) [61]. The formation of the intermediate boron enolate was confirmed by H NMR spectroscopy [66,67]. The role of water present in the system is to hydrolyze the boron enolate and to prevent its degradation by undesired free-radical processes. This hydrolysis step is essential when alkynones [68] and acrylonitrile [58] are used as radical traps since the resulting allenes or keteneimines respectively, react readily with radical species. Maillard and Walton have shown by nB NMR, ll NMR und IR spectroscopy, that tri-ethylborane does complex methyl vinyl ketone, acrolein and 3-methylbut-3-en-2-one. They proposed that the reaction of triethylborane with these traps involves complexation of the trap by the Lewis acidic borane prior to conjugate addition [69]. 

Armstrong attributed the increased resistance of dentin matrix to proteolysis to the blockage of susceptible sites by covalently bound carbohydrate. Later it became clear that the Maillard reaction induces the formation of covalent bonds (cross-links) between protein molecules, accounting for such resistance as well. The presence of non-degradable matrix proteins inhibits mineral dissolution (Chapter 2). In addition, both brown pigments and cross-linked proteins inhibit the production of extracellular polysaccharides by cariogenic streptococci (Kobayashi et al., 1990). 

The Maillard condensation is one of the most extensively studied reactions within the field of degradation chemistry, particularly in the area of food and nutritional science. Louis Mallard reported in 1912 that some amines react with reducing carbohydrates to produce brown pigments. The condensation typically yields a simple glycosylamine, which then readily undergoes the Amadori rearrangement to produce 1 -amino-1 -deoxy-2-ketoses [95]. Reducing carbohydrates... 

The formation of brown pigments via the Maillard reaction, especially in model systems (e.g. glucose-glycine), usually follows zero-order kinetics, but the loss of reactants has been found to follow first- or second-order kinetics in foods and model systems. Activation energies of 109, 116 and 139 kJ mol-1 have been reported for the degradation of lysine, the formation of brown pigments and the production of hydroxymethylfurfural (HMF), respectively. 

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