Glucose Maillard reaction

Chemical degradation of amino acids such as glutamin, cysteine reaction of amino-acids with glucose (Maillard reaction)... 

Egg white is composed of about 10% protein and 0.5% glucose. Maillard reaction of egg white proteins with glucose proceeds during the production of dried egg white powder, resulting in the formation of brownish pigments and the alteration of powdered protein functional properties such as solubility, emulsifying activity, gelling property (4). 

YOKDTA A, MiYATA K, MURAGUCHi H and TAKAHASHi A (1987) Effect of glucose on the antioxidative activity of Maillard reaction products during extmsion cooking , Nippon Nogeikagaku Kaishi, 61 (10) 1273-8. 

When the Maillard reaction was evaluated using 10 g/1 glucose for 30 minutes at 90 °C and 20 1 liquor ratio the fibre diameter increased by 3.5% xylose gave an increase almost twice as much but showed some yellowing. In this process accessibility of the fibre for dye molecules is increased, since the glucose molecules penetrate between the peptide chains. The reaction also introduces primary alcoholic groups, making the wool more dyeable with... 

At present, antioxidants are extensively studied as supplements for the treatment diabetic patients. Several clinical trials have been carried out with vitamin E. In 1991, Ceriello et al. [136] showed that supplementation of vitamin E to insulin-requiring diabetic patients reduced protein glycosylation without changing plasma glucose, probably due to the inhibition of the Maillard reaction. Then, Paolisso et al. [137] found that vitamin E decreased glucose level and improved insulin action in noninsulin-dependent diabetic patients. Recently, Jain et al. [138] showed that vitamin E supplementation increased glutathione level and diminished lipid peroxidation and HbAi level in erythrocytes of type 1 diabetic children. Similarly, Skyrme-Jones et al. [139] demonstrated that vitamin E supplementation improved endothelial vasodilator function in type 1 diabetic children supposedly due to the suppression of LDL oxidation. Devaraj et al. [140] used the urinary F2-isoprostane test for the estimate of LDL oxidation in type 2 diabetics. They also found that LDL oxidation decreased after vitamin E supplementation to patients. 

Figures 4.2.1 and 4.2.2 [4.9] show sorption isotherms 1, for such products which become less hygroscopic with increased temperature, or 2, for glucose, fats and oils which become more hygroscopic with increased temperature. Since freeze drying lowers aw values, the growth of bacteria, fungus and yeast below aw = 0.8 is reduced, or impossible. On the other hand, the Maillard reaction increases with decreasing aw up to a maximum at aw 0,6-0,7,...

Several markers for the Maillard reaction have been described in the literature. For example, the product initially formed between glucose and lysine is partly transformed into furosine (Heyns et ah, 1968) on acid hydrolysis. Conversely, the fluorescent amino acid pentosidine (Sell and Monnier, 1989) is an advanced glycation endproduct (AGE) and may form covalent bonds between proteins (cross-linking). Furthermore, the Maillard reaction leads to an increase in characteristic fluorescence (excitation 370 nm, emission 440 nm) (Monnier et ah, 1984 Pongor et ah, 1984). 

The aim of this study was to find proof that the Maillard reaction can take place in demineralized dentin. Markers for the initial and advanced Maillard reaction as well as physiological cross-links were investigated after incubation of bovine dentin with glucose. Changes in susceptibility to protein-degrading enzymes and in fluorescence specific for the reaction were additionally measured. 

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). 

The aim of this study was to verify previous conclusions that dentin collagen resists enzymatic attack after reaction with glucose. The results show that, following the Maillard reaction, dentin collagen indeed is less degraded by pepsin, but not by trypsin. 

Chapter 4 describes the in vitro reaction of glucose wifh demineralized dentin. Preliminary tests revealed that use of disfilled insfead of deionized water accelerated browning, consistent with the effect of frace metals on the Maillard reaction. The yellow discolored slices were more resistant than controls to pepsin-mediated breakdown, but not to trypsin-mediated breakdown. It would be worthwhile to investigate proteolysis of denfin collagen covalently bound by the Maillard reaction to proteins, which penetrate into a caries lesion. 

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. 

To study the effect of the Maillard reaction on nutritive value of protein, Patton, et a l. (57) heated purified casein and soybean globulin in 57. glucose solution for 24 hrs at 96.5°C, and found significant losses of lysine, arginine, tryptophan, and histidine (52). 

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