Lactose, physical properties

Milk consists of 85—89% water and 11—15% total soflds (Table 1) the latter comprises soflds-not-fat (SNF) and fat. Milk having a higher fat content also has higher SNF, with an increase of 0.4% SNF for each 1% fat increase. The principal components of SNF are protein, lactose, and minerals (ash). The fat content and other constituents of the milk vary with the animal species, and the composition of milk varies with feed, stage of lactation, health of the animal, location of withdrawal from the udder, and seasonal and environmental conditions. The nonfat soflds, fat soflds, and moisture relationships are well estabhshed and can be used as a basis for detecting adulteration with water (qv). Physical properties of milk are given in Table 2. 

The book assumes a knowledge of chemistry and biochemistry but not of dairy chemistry. As the title suggests, the book has a stronger biochemical orientation than either Principles of Dairy Chemistry or Dairy Chemistry and Physics. In addition to a fairly in-depth treatment of the chemistry of the principal constituents of milk, i.e. water, lactose, lipids, proteins (including enzymes), salts and vitamins, various more applied aspects are also covered, e.g. heat-induced changes, cheese, protein-rich products and the applications of enzymes in dairy technology. The principal physical properties are also described. 

Table 2.3 Some physical properties of the two common forms of lactose (modified from Jenness and Patton, 1959)...

Milk is a dilute emulsion consisting of an oil/fat dispersed phase and an aqueous colloidal continuous phase. The physical properties of milk are similar to those of water but are modified by the presence of various solutes (proteins, lactose and salts) in the continuous phase and by the degree of dispersion of the emulsified and colloidal components. 

Ross, K. D. 1978A. Effects of methanol on physical properties of a- and /3-lactose. J. Dairy Sci. 61, 152-158. 

The presence of amorphous lactose in the excipient may have a negative effect on compactibility and product stability. Direct compression grades of lactose monohydrate are available as granulated/agglomerated particles from multiple vendors. These physical properties are listed in Table 7.4. Commercial products combine the good flowability of coarse lactose crystals and the good compressibility... 

TABLE 7.4 Typical Physical Properties of Selected Lactose as Directly Compressible Filler-Binders... 

Anhydrous lactose is a free-flowing crystalline /3-lactose without water of hydration, first described in the literature in 1966.33 It is available in a white crystalline powder that has good flowability and high compactibility. Anhydrous lactose can be reworked or milled, resulting in a smaller loss of compactibility than with other forms of lactose (due to its high fragmentation propensity). Table 7.4 lists the physical properties of the product. The product is very suitable for moisture-sensitive chug formulations. 

Table 4-6 Some Physical Properties of the Two Common Forms of Lactose...

Jones, T.M. Pilpel, N. Some physical properties of lactose and magnesia. J. Pharm. Pharmacol. 1965, 17, 440. 

Other physical properties of lactose solutions that have been investigated include the rate of crystallization, density, viscosity, rc-... 

Lactose is widely used as a filler or diluent in tablets and capsules, and to a more limited extent in lyophilized products and infant formulas.Lactose is also used as a diluent in dry-powder inhalation. Various lactose grades are commercially available that have different physical properties such as particle size distribution and flow characteristics. This permits the selection of the most suitable material for a particular application for example, the particle size range selected for capsules is often dependent on the type of... 

Table II Typical physical properties of selected commercially available lactose, monohydrate.

A number of different grades of lactose are commercially available that vary in their physical properties and many studies have been reported in the literature comparing the behavior of these various materials in different formulations. A number of co-processed excipients which contain lactose are available for direct-compression applications co-processed lactose and starch (Starlac, Meggle/Roquette Freres), lactose and microcrystalline cellulose Microcelac, Meggle) lactose and cellulose powder (Cellactose, Meggle), lactose, povidone, and crospovidone (Ludipress, BASF). 

Thwaites PM, Mashadi AB, Moore WD. An investigation of the effect of high speed mixing on the mechanical and physical properties of direct compression lactose. Drug Dev Ind Pharm 1991 17 503-517. 

Fell JT, Newton JM. The production and properties of spray-dried lactose, part 2 the physical properties of samples of spray-dried lactose produced on an experimental drier. Pharm Acta Helv 1971 46 425 30. 

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