Crystallization spray-dried lactose

Polyethylene glycol (PEG) 4000, when spray-dried with lactose, has been shown to accelerate the rate and extent of crystallization of lactose. It has also been shown that spray-dried lactose composite particles containing an ion complex of chitosan are suitable for the dry-coating of tablets. Spray-dried lactose and crystallized spray-dried lactose have been evaluated for dry powder inhalation.Amorphous spray-dried lactose has also been studied in composites with PVP. ... 

A faulty batch of tablets can sometimes be recovered by grinding up the tablets and recompressing them, a process which is known as reworking and is analogous to the dry granulation method of tablet manufacture. This can sometimes cause problems with a direct compression formulation. Many direct compression diluent particles are in the form of aggregates, e.g., spray-dried lactose is composed of small crystals of lactose embedded in amorphous lactose. If these aggregates are compressed, their structure may be broken down to such an extent that subsequent recompression will result in impaired tablet quality. 

The Ter (onset) of spray-dried and freeze-dried materials obtained from dynamic DSC analysis are shovm in Figure 44.3 with respective water contents. The decreased with increasing water activities and water contents showing a similar behavior as Tg. T of freeze-dried lactose was higher than T r of spray-dried lactose in the anhydrous state and at all corresponding water contents (Figure 44.3). T for freeze-dried lactose was nearly the same as reported by Roos and Karel (1990) for freeze-dried anhydrous and humidified lactose over various RVP. Crystallization of lactose also occurred differently from differently dehydrated materials. 

The present study has shovm that spray-dried and freeze-dried lactose have different physical structures, thermal transitions, and time-dependent lactose crystallization behavior. Spray-dried lactose had round-shaped particles but freeze-dried lactose resembled broken glass or had a flakelike structure. Tg and Tq. of freeze-dried lactose were higher than those of... 

Haque, M.K. and Roos, Y.H. Water plasticization and crystallization of lactose in spray-dried lactose/protein mixtures, /. Food Sci., 69, 23, 2004. 

FIGURE 3.24 DSC curves for (a) 100% amorphous spray-dried lactose, (b) commercial 15% amorphous spray-dried lactose, (c) crystalline a-lactose monohydrate, and (d) crystallized 15% amorphous spray-dried lactose. (Reproduced from Sebhatu, T., Elamin, A.A., and Ahlneck, C., Pharm. Res., 11, 1233, 1994. With permission.)... 

Frequently, the spray drying process yields amorphous materials, which undergo crystallization upon storage or exposure to suitable environmental conditions. The effect of various additives on the recrystallization of amorphous spray-dried lactose has been studied [36]. The... 

The quality of a product may depend on the amorphousness within a sample. Spray-dried lactose is a term that embraces several types of products, depending on how the product was manufactured. If a suspension of a-lactose monohydrate is spray dried, the lactose in solution acts as a binder during the spraying process to bind the crystals of lactose together as aggregates. Thus, the predominant nature of a-lactose is maintained. The amorphousness of the... 

Lactose may be obtained in two crystalline forms a-lactose and P-lactose (in addition to amorphous forms). The alpha form is obtained when water is incorporated into the lattice structure during crystallization (usually by supersaturation below 93.5°C) (5). Alternatively, the beta form does not contain water and exists as a non-hygroscopic and anhydrous form. Amorphous lactose is formed when either the crystallization is rapid or sufficient transient energy is introduced into the crystalline forms (74), i.e., spray drying (75), micronization and milling (76), freeze-drying, and anti-solvent crystallization (77). 

Lactose glass. When a lactose solution is dried rapidly, viscosity increases so quickly that crystallization is impossible. A noncrystalline form is produced containing a- and /J-forms in the ratio at which they exist in solution. Lactose in spray-dried milk exists as a concentrated syrup or amorphous glass which is stable if protected from air, but is very hygroscopic and absorbs water rapidly from the atmosphere, becoming sticky. 

Even though liquid whey has been successfully commercialized in the form of alcoholic and nonalcoholic beverages, these are still a rarity in most countries. Most whey is converted to whey solids as ingredients for human food or animal feeds by traditional processes such as spray drying, roller drying, concentration to semisolid feed blocks, or production of sweetened condensed whey. Jelen (1979) reported other traditionally established processes including lactose crystallization from untreated or modified whey, production of heat-denatured whey protein concentrate, or recovery of milk fat from whey cheese in whey butter. ... 

When a lactose solution is dried rapidly, its viscosity increases so quickly that crystallization cannot take place. The dry lactose is essentially in the same condition as it was in solution, except for removal of the water. This is spoken of as a concentrated syrup or an amorphous (noncrystalline) glass. Various workers have shown conclusively that lactose in milk powder (spray, roller, or freeze-dried) is noncrystalline and exists in the same equilibrium mixture of a- and /3-lactose as existed in the milk prior to drying (Zadow 1984). 

Crystallization of the lactose in concentrated skim milk (40 to 54% total solids) can result in rapid increases in viscosity even during the short interval between concentration and spray drying (Baucke and Sanderson 1970). 

A general, recent trend has been to apply the principles of ion exchange to the purification of whey or lactose solutions. Anionic and cationic exchange resins are used to remove impurities from the solution, which can then be condensed and crystallized or spray-dried directly. Ahlgren (1977) and Delaney (1976) have reviewed developments... 

Saito, Z. 1985. Particle structure in spray-dried whole milk and in instant skim milk powder as related to lactose crystallization. Food Microstruct. 4, 333-340. 

Haque, K., and Roos, Y.H. (2005). Crystallization and x-ray diffraction of crystals formed in water-plasticized amorphous spray-dried and freeze-dried lactose-protein mixtures. Car-bohydr. Res. 340,293-301. 

A suspension of a-lactose monohydrate crystals in a lactose solution is atomized and dried in a spray drier. Approximately 10-20% of the total amount of lactose is in solution and the remaining 80-90% is present in the crystalline form. The spray-drying process predominantly produces spherical particles. The compactibility of the material and its flow characteristics are a function of the primary particle size of the lactose monohydrate and the amount of amorphous lactose. " ... 

Physical Structure, Water Plasticization, and Crystallization of Spray-Dried and Freeze-Dried Lactose... 

Instant crystallization temperature (onset) for spray-dried and freeze-dried lactose as a function of water content, determined using DSC during heating at 5°C/min. 

Saltmarch, M. and Labuza, T.P SEM investigation of the effect of lactose crystallization on the storage properties of spray-dried whey. Scan. Electron Microsc., 3, 659,1980. 

---