Glucose-casein reaction

A control diet was prepared as follows Tha labelled egg-white protein was mixed with a basal diet in the proportion 2 98. The basal diet contained 10% casein, 10% sucrose, about 70% starch and 5% maizeoil, as well as vitamins and minerals. A small amount of [sHl-lysine was added to this mixture, giving a ratio of tritium to (11 C) dpm of approximately 10 1. The experimental diet was obtained by adding a small amount ot the glucose-lysine reaction mixture to the control diet. 

The reaction of sugar with protein becomes irreversible. For example, in a model system, after glucose incubation with casein, no glucose... 

Lea, C. H. and Hannan, R. S. 1950. Studies of the reaction between proteins and reducing sugars in the dry state. II. Further observations on the formation of the casein-glucose complex. Biochem. Biophys. Acta 4, 518-531. 

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). 

Lysine, like other amino acids, can also be decomposed by heating. The early work of Lea and Hannan showed that the destruction and cross-linking of lysine with sugars took place in the reaction between glucose and casein (19) ... 

Figure 1.2. Differential thermal analysis for the humic acid fraction isolated in NaOH from a sapric histosol (1), from the acid precipitate isolated from products of the reaction of meth-ylglyoxal with glycine (2), and from the acid precipitate formed from the reaction of glucose with glycine (3), alkali lignin (4), casein (5), lignin-casein 3 1 complex (6), and lignin-casein 6 1 complex (7).

Ketoses undergo a similar series of reactions, leading to 2-amino-2-deoxyaldoses (Heyns rearrangement). However, browning reactions of fructose differ from those of glucose, e.g., loss of amino acid or of free amino groups (casein) is much lower.28... 

Lee, J. T., and Woo, K. L. (1988). Effect of preventing the Maillard reaction between casein and glucose with corn syrup and sucrose. Korean J. Food Sci. and Technol. 20 526-535 (Food Sci. Technol. Abstr. 5A13, 1989). 

Casein-Bound 3H Lysine in Untreated, Early, and Advanced Maillard Casein (41). Goat sodium caseinate biologically labelled with L-4,5-3H-lysine was treated with glucose under conditions inducing early and advanced Maillard reactions. The two preparations contained about the same reactive lysine (see Table III) the early Maillard 3H-casein contained only c-deoxyfructosyllysine as Maillard products and the advanced Maillard 3H-casein contained some c-deoxy-fructosyllysine and unidentified derivatives of lysine and glucose as brown pigments. 

In Fig. 23, the role of moisture in bimolecular reactions is classified by Hageman into three cases. The increases in reaction rate are attributed to a change in state of the water associated with the solid as reflected by a lower effective viscosity. In Case I, there is a continual increase in reaction rate with increasing water content above the monolayer. When all the reactant has been solubilized and further water dilutes the medium. Case II results. If the dilution is extensive, or if water is a product inhibitor of decomposition, a rate reduction can be observed (Case III). Case III behavior is an example of the effect of moisture on the progress of the Malliard reaction for the glucose-containing formulations of a-A-acetyl-L-lysine, poly-L-lysine, insulin, casein, and plasma proteins. " The fact that there can be a maximum degradation rate at a humidity other than 100% RH is observed in other situations as well. 

If one could conclusively show that there is an effect of plasticizers on reaction rate that is independent of moisture content or a , then this would demonstrate the significance of matrix properties for governing reaction rate. Labuza et al. (1977) studied the Maillard reaction and measured the effects of several parameters. These included temperature, reactant concentration, pH, buffers, and the addition of humectants. The formulation consisted of glucose and casein as reactants within a carrier matrix of microcrystalline cellulose and an inert lipid. Reaction rate was measured both as glucose loss, lysine loss, and pigment production (A42o). 

PG peptide (casein hydrolyzate)-glucose reaction mixture. 

Mayaudon et al. also showed that the casein-hydrolysing activities of soil extracts were poorly correlated to microbial numbers in soils. Ladd and Paul demonstrated with a glucose-amended soil that the highest activities of proteinases towards casein were achieved during a rapid phase of turnover of microbial cells and of net decline in microbial cell numbers, at which time equivalent to 14% of the net gain in soil caseinase activity was extractable with a dilute bicarbonate solution. Nannipieri et reported that the casein activities of pyrophosphate extracts of tw o soils were equivalent to about 60% of the activities of the respective unextracted soils and, in the case of a third soil, to about 140%, indicative of higher active enzyme concentrations or higher specific activities due perhaps to facilitation of enzyme-substrate reactions in extracts. 

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