Lactose phase composition

To illustrate the utility of TG analysis for such determinations, a series of calibration samples were prepared at levels approximately 90% or 10% in the monohydrate phase, using anhydrous /1-lactose as a diluent in bulk a-monohydrate.48 These were subjected to a standard TG evaluation, and the results of the analysis are shown in Table 1. The results indicate that the TG method yields reasonable estimations of the phase composition, but that the difference between measured and found compositions could be unacceptably large for some applications. The data appear to indicate the existence of a small positive bias, which was found to be worse in the 10% monohydrate samples. In a properly controlled and validated system, however, it is highly likely that method limitations could be overcome and TG analysis appropriately used for quantitative analysis of phase composition. 

In a wide-ranging study, NIR spectroscopy was used to quantitate the phase composition in various forms of sulfamethoxazole, sulfathiazole, lactose, and ampicillin.80 For instance, as shown in Figure 4, the o -mono-hydrate phase of lactose is easily distinguished from /Mactose anhydrate on the basis of the characteristic band at 1940 nm associated with the water combination mode. In all cases, however, properly calibrated NIR methods were able to yield good predictions of phase composition relative to the actual composition of the standards used, and it was concluded that the quantitative NIR was equally effective for such work as other commonly used quantitative methods. 

The retention behavior of fructose, glucose, sucrose, maltose, and lactose on various aminopropyl columns (RI detector) was studied using an 80/20 acetonitrile/water mobile phase. Elution for all compounds was complete in 15-20 min with all peaks well resolved. This method, or one very similar to it, is used for the sugar analyses of a wide variety of food products. For example, a food sample that contains elevated salt levels poses a problem for sugar analyses since the chloride ion can coelute with fructose under normal conditions [1204]. In this work, the optimal mobile phase composition of 70/30 acetonitrile/water (on an aminopropyl colunm) had to be modified to 75/25 in order to shift the retention of the first-eluting sugar (fructose) past the elution time of chloride (here 4 min or Ji/ 1). Standards of n oWn w/w were made and 25 uL was injected. 

A phase can be defined as a domain bounded by a closed surface in which parameters such as composition, temperature, pressure and refractive index are constant but change abruptly at the interface. The principal phases in milk are its serum and fat and the most important interfaces are air/serum and fat/serum. If present, air bubbles, and ice, fat or lactose crystals will also constitute phases. Forces acting on molecules or particles in the bulk of a phase differ from those at an interface since the former are attracted equally in all directions while those at an interface experience a net attraction towards the bulk phase (Figure 11.6). 

Protein Composition of Milk. Skim milk is a colloidal suspension of extreme complexity. The particulate phase, the casein micelles, consists primarily of a mixture of asi, as2, / , and x-caseins combined with calcium ions and an amorphous calcium-phosphate-citrate complex. The soluble phase contains lactose, a fraction of the caseins and calcium, and, in raw milk, the whey proteins, which are predominantly /3-lacto-globulin and a-lactalbumin. When milk is centrifuged at high speed (in our experiments, 30 min at 110,000 X gravity), the casein micelles sediment. This permits one to separate the two physical phases of skim milk and to measure changes in composition of the phases resulting from... 

Size as well as inner structure of the WPP depend on the reaction conditions in terms of the temperatnre regime and the medium composition. As shown by Plock et al. (1997) and by Spiegel (1999), the lactose content in the aqueous phase is of great influence. Figure 19.11 shows the resulting aggregate size of the WPP,... 

Milk is a liquid secretion of the mammary glands of female mammals, consisting of 80-90% water and 10-20% dry mass. It is an oil-in-water (OAV) emulsion composed of fat and fat-soluble vitamins the aqueous phase contains proteins, mineral salts, lactose, and water-soluble vitamins. The chemical composition of milk (Table 2.1) depends on species and breed, lactation period, and nutritional and health conditions of the animal. 

---