Lactose browning

Ferretti A. and Flanagan V.P. (1973) Characterization of volatile constituents of an V-alpha-formyl-i-lysinc-D-lactose browning system. J. Agric. Food Chem. 21, 35-7. 

Action of sodium hydroxide. Boil about 0 2 g. of glucose with 5 of 10% NaOH solution the mixture turns yellow, then brown, and emits the odour of caramel. Fructose, maltose, lactose and soluble starch behave similarly sucrose and ordinary starch do not give colorations. 

Pharmaceutical tablets coated with lactose often develop a brown discoloration. The factors that primarily affect the... 

Caramel. Officially, the color additive caramel is the dark brown Hquid or soHd material resulting from the carefully controlled heat treatment of the following food-grade carbohydrates dextrose, invert sugar, lactose, malt symp, molasses, starch hydrolysates and fractions thereof, or sucrose. Practically speaking, caramel is burned sugar. 

The reaction of a primary amine with lactose is accompanied by a browning of the solids, and the path of such reactions is easily following by means of diffuse reflectance spectroscopy. For instance, the reaction of isonicotinic acid hydrazide (Isoniazid) with lactose could be followed through changes in the reflectance spectrum [31]. As may be seen in Fig. 4, a steady decrease in reflectance was noted as the sample was heated for increasing amounts of time. The spectral data were used to deduce the rate constants for the browning reaction at various heating temperatures, and these rates could be correlated with those... 

The reaction of neomycin with many compounds has been described in Section 3, hence numerous reports of neomycin incompatibility may be expected. Dale and Rundman have extensively reviewed the compatibility of neomycin with substances that may be encountered by the formulation pharmacist. Kudalker et al 03 have described the incompatibility of the antibiotic with rancid oils, and the incompatibility with bentonite, a montomorill-onite clay, has been reported by Danti and Guth306. The incompatibility with lactose, causing a discoloration of the mixture has been studied by Hammouda and Salakawy- 0 . The amount of browning produced was shown to be dependant on the initial pH of the solution. The rate of discoloration of the lactose/neomycin powder was directly related to the temperature of storage and the relative humidity of the atmosphere. Discoloration was overcome by addition of sodium bisulphite. 

The factors affecting the Maillard reaction include temperature, time, moisture content, concentration, pH, and nature of the reactants. - It has been shown that, out of 21 amino acids, glycine, lysine, tryptophan, and tyrosine provide the most intense browning when exposed to five saccharides, especially a-lactose. The Maillard reaction is also responsible for the decreased availability of lysine in proteinaceous foods. 

When sugars are treated with aqueous ammonia for a short time at low temperature in the absence of a catalyst, the reaction is arrested before heterocyclic compounds can be formed in appreciable proportion, and the products are mainly epimerization products of the sugars, probably formed by way of their 2,3-enediols. These epimerization products are summarized in Table I which shows the reactions of D-glucose, D-fructose, lactose, maltose, and melibiose with aqueous ammonia for a short time at low temperature. A dark-colored, high polymer is also formed in some instances (the browning reaction). In the ammoniacal solution, the monosaccharides are epimerized the disaccharides are epimerized and, in addition, may be hydrolyzed to monosaccharides that can also be epimerized hence, the variety of products obtained may be considerable. 

Figure 9.1 The time needed (t ) at various temperatures (T) to inactivate some enzymes and cryoglobulins to kill some bacteria and spores to cause a certain degree of browning to convert 1 % of lactose to lactulose to cause heat coagulation to reduce available lysine by 1 % and to make 10% and 75% of the whey proteins insoluble at pH 4.6 (from Walstra and Jenness,...

The initial Schiff base is digestible but after the Amadori rearrangement, the products are not metabolically available. Since lysine is the amino acid most likely to be involved and is an essential amino acid, Maillard browning reduces the biological value of proteins. Interaction of lysine with lactose renders the adjacent peptide bond resistant to hydrolysis by trypsin, thereby reducing the digestibility of the protein. 

Lactose and casein are the two principal reactants in the browning of milk products, but dried whey products containing lactose also undergo browning. Holsinger et al. (1973) studied the variation of total and available lysine in dehydrated products from cheese wheys by different processes. Roller-dried products showed significant losses in ly-... 

Ferretti, A. and Flanagan, V. P. 1971. The lactose-casein (Maillard browning-system. Volatile components. J. Agri. Food Chem. 19, 245-249. 

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