title: Moisture sorption, compressibility and caking of lactose polymorphs.
abstract: The aim of this study was to conduct storage studies on the moisture sorption and caking properties of lactose powder containing different polymorphs (i.e. alpha-monohydrate, alpha-anhydrous unstable, alpha-anhydrous stable, beta-anhydrous) and spray-dried lactose. The dry sample was compacted using a texture analyzer in paper cylinders and stored at relative humidity (RH) of 33%, 43%, 57% and 75% (25 degrees C, for 3 months). The samples were monitored for weight gain, moisture content, alpha/beta balance and hardness. A simple new method of powder compression for measuring the degree of hardness of caked lactose was developed using a texture analyzer. Clear distinctions were found in the storage behavior of the five different samples. Storage at various RHs caused severe caking to beta-lactose anhydrous and spray-dried lactose. The beta-lactose anhydrous was hygroscopic at 75% RH. The spray-dried lactose, which contained some amorphous lactose, was hygroscopic at all RHs studied. Its moisture sorption behavior differed from that of its major component, alpha-lactose monohydrate, by initially absorbing moisture then desorbing. alpha-Lactose monohydrate was less hygroscopic at 75% RH and it formed friable cakes. The alpha-lactose anhydrous stable was hygroscopic at 75% RH and initially formed hard cakes which became friable during storage. The unstable form of anhydrous alpha-lactose was hygroscopic at all levels of RH studied but did not cake.
authors.affiliation: Plant and Food Science Centre, University of Western Sydney, Penrith South DC, NSW 1797, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Listiohadi
authors.forename: J A
authors.initials: JA
authors.lastname: Hourigan
authors.forename: R W
authors.initials: RW
authors.lastname: Sleigh
authors.forename: R J
authors.initials: RJ
authors.lastname: Steele
mesh_terms: D000327:Adsorption; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D004355:Drug Stability; D004356:Drug Storage; D005079:Excipients / Q000737:chemistry*; D006244:Hardness; D006813:Humidity; D007785:Lactose / Q000737:chemistry*; D011208:Powders / Q000737:chemistry
chemical_list: D005079:Excipients; D011208:Powders; D007785:Lactose