title: Physical stability of a microcrystalline beta-sitosterol suspension in oil.
abstract: Sterols have been shown to reduce plasma cholesterol by blocking the absorption of cholesterol from the gut. The physical properties of crystalline plant sterols limit their use in foods. A coarse-grained structure can be avoided by recrystallisation, a method that affords a reduction in the particle size. A previous work described how to produce a microcrystalline beta-sitosterol suspension. The present study deals with the stability of that suspension. Recrystallisation was carried out by two different methods; one based on rapid the other based on slow cooling, whereby six different compositions were made containing 5-30% of beta-sitosterol and secondly either 5 or 20% water was added. The particle size and habit were evaluated during a 16 weeks storage period (+4 or -19 degrees C) by way of optical microscopy. The crystal structure and degree of crystallinity was analysed by X-ray diffraction. Suspensions can, in most cases, be stored for 16 weeks without any changes to the size and habit. The only evidence of crystal growth came from a suspension with a low sterol concentration at a temperature of +4 degrees C. This is due to the dissolution-diffusion process which is affected by temperature and viscosity. Suspensions containing higher amounts of sterol remained stable, if stored at +4 or -19 degrees C, for 16 weeks. The suspensions included both hemihydrous and monohydrous beta-sitosterol crystals. Suspensions containing less sterol showed greater amounts of monohydrated crystals. This illustrates more water penetration into the crystals. A higher sterol concentration led to a larger number of smaller crystals creating reflections similar to hemihydrated crystals.
authors.affiliation: Department of Pharmacy, University of Helsinki, Helsinki, Finland. anna.vonbonsdorff@helsinki.fi
authors.forename: Anna
authors.initials: A
authors.lastname: von Bonsdorff-Nikander
authors.forename: Milja
authors.initials: M
authors.lastname: Karjalainen
authors.forename: Jukka
authors.initials: J
authors.lastname: Rantanen
authors.forename: Leena
authors.initials: L
authors.lastname: Christiansen
authors.forename: Jouko
authors.initials: J
authors.lastname: Yliruusi
mesh_terms: D002784:Cholesterol / Q000031:analogs & derivatives* / Q000737:chemistry; D004355:Drug Stability; D000960:Hypolipidemic Agents / Q000737:chemistry*; D010840:Phytosterols; D012855:Sitosterols / Q000737:chemistry*; D012987:Soil; D013535:Suspensions; D013997:Time Factors; D014783:Viscosity; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D000960:Hypolipidemic Agents; D010840:Phytosterols; D012855:Sitosterols; D012987:Soil; D013535:Suspensions; D014867:Water; C021273:campesterol; C025473:gamma-sitosterol; D002784:Cholesterol