Lactose reducing properties

Because of their speed and reasonable instrumental requirements, there is continuing interest in colorimetric procedures for lactose determinations. Most procedures are based on the reducing properties of lactose samples that contain only one sugar are easily measured colori-metrically, but samples with three or four sugars may require several different colorimetric assays to determine the composition accurately. 

Dextrose is widely used in solutions to adjust tonicity and as a sweetening agent. Dextrose is also used as a wet granulation diluent and binder, and as a direct-compression tablet diluent and binder, primarily in chewable tablets. Although dextrose is comparable as a tablet diluent to lactose, tablets produced with dextrose monohydrate require more lubrication, are less friable, and have a tendency to harden. The mildly reducing properties of dextrose may be used when tableting to improve the stability of active materials that are sensitive to oxidation. 

Lactose is a disaccharide reducing sugar. Unlike the other sugars mentioned, lactose is not particularly soluble. A property that has some use in yeast-containing products is that lactose is not fermented by baker s yeast. 

The properties of disaccharides aren t a simple combination of the properties of the two monosaccharides present. For example, the disaccharide lactose (milk sugar) is a reducing sugar containing a (3-D-glucose linked to a D-galactose molecule. 

Controlled optimal particle size and size distribution ensures superior flow properties of coprocessed excipients and reduced reliance on addition of glidants. The volumetric flow properties of SMCC were studied in comparison with those of the physical mixture of its parent excipients (42). The particle size range of the two test samples was found to be similar, but the flow of coprocessed excipient was better than that of the physical mixture. A comparison of the flow properties of Cellactose with its parent excipients was also performed (5) by measuring the angle of repose and Hausner ratio, and Cellactose was found to have better flow characteristics than lactose or a physical mixture of cellulose and lactose. The spray-dried coprocessed product had a spherical shape and even surfaces, which resulted in improved flow properties. On similar terms, mechanically coating the 2% CSD over microfine cellulose powder resulted in improving its flow properties (43). 

The chemistry and physicochemical properties of lactose, a reducing disaccharide containing galactose and glucose linked by a / (l-4)-bond, were described in Chapter 2. 

Lactose anhydrous has been used experimentally in hydrophilic matrix tablet formulations and evaluated for dry powder inhalation applications. Partial hydration of anhydrous lactose increases the specific surface area and reduces the flow properties of powders but has no effect on compactibility. A specification for lactose is included in the Food Chemicals Codex (FCC) see Factose, Monohydrate. The EINECS number for lactose anhydrous is 200-559-2. 

Similar behavior has been observed for noncrystallizing polymers. For example, the diffusivity of water in poly(vinylpyrrolidone) (PVP) (Oksanen and Zografi, 1993) has been shown to increase at water contents beyond the hydration limit. Additional reports have shovm that the hydration limit has physical significance for other polymer excipients. Microcrystalline cellulose and lactose for compression, for example, lose their direct compaction properties at water contents just below (Huettenrauch and Jacob, 1977), and gelatin capsules become brittle as the water content is reduced below Wm (Kontny and Mulski, 1989). Recently, the chemical stability of a model peptide in PVP matrices was shown to improve when the amorphous dispersion was stored below the polymer s hydration limit (Lai et al., 1999a Lai et al., 1999b Lechuga-Ballesteros et al., 2002). 

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