title: Elucidation of density profile of self-assembled sitosterol + oryzanol tubules with small-angle neutron scattering.
abstract: Small-angle neutron scattering (SANS) experiments have been performed on self-assembled tubules of sitosterol and oryzanol in triglyceride oils to investigate details of their structure. Alternative organic phases (deuterated and non-deuterated decane, limonene, castor oil and eugenol) were used to both vary the contrast with respect to the tubules and investigate the influence of solvent chemistry. The tubules were found to be composed of an inner and an outer shell containing the androsterol group of sitosterol or oryzanol and the ferulic acid moieties in the oryzanol molecule, respectively. While the inner shell has previously been detected in SAXS experiments, the outer shell was not discernible due to similar scattering length density with respect to the surrounding solvent for X-rays. By performing contrast variation SANS experiments, both for the solvent and structurant, a far more detailed description of the self-assembled system is obtainable. A model is introduced to fit the SANS data; we find that the dimensions of the inner shell agree quantitatively with the analysis performed in earlier SAXS data (radius of 39.4 +/- 5.6 angstroms for core and inner shell together, wall thickness of 15.1 +/- 5.5 angstroms). However, the newly revealed outer shell was found to be thinner than the inner shell (wall thickness 8.0 +/- 6.5 angstroms). The changes in the scattering patterns may be explained in terms of the contrast between the structurant and the organic phase and does not require any subtle indirect effects caused by the presence of water, other than water promoting the formation of sitosterol monohydrate in emulsions with aqueous phases with high water activity.
authors.affiliation: Unilever Research and Development Vlaardingen, Olivier van Noortlaan 120, NL-3133 AT Vlaardingen, The Netherlands. arjen.bot@unilever.com
authors.forename: Arjen
authors.initials: A
authors.lastname: Bot
authors.forename: Elliot P
authors.initials: EP
authors.lastname: Gilbert
authors.forename: Wim G
authors.initials: WG
authors.lastname: Bouwman
authors.forename: Hassan
authors.initials: H
authors.lastname: Sawalha
authors.forename: Ruud
authors.initials: R
authors.lastname: den Adel
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Paul
authors.initials: P
authors.lastname: Venema
authors.forename: Erik
authors.initials: E
authors.lastname: van der Linden
authors.forename: Eckhard
authors.initials: E
authors.lastname: Flöter
mesh_terms: D000473:Alkanes; D002368:Castor Oil / Q000737:chemistry; D053138:Cyclohexenes / Q000737:chemistry; D003903:Deuterium; D005054:Eugenol / Q000737:chemistry; D000077222:Limonene; D033363:Neutron Diffraction; D010666:Phenylpropionates / Q000737:chemistry*; D053838:Scattering, Small Angle; D012855:Sitosterols / Q000737:chemistry*; D013729:Terpenes / Q000737:chemistry; D014280:Triglycerides / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000473:Alkanes; D053138:Cyclohexenes; D010666:Phenylpropionates; D012855:Sitosterols; D013729:Terpenes; D014280:Triglycerides; D005054:Eugenol; D002368:Castor Oil; D000077222:Limonene; D003903:Deuterium; C012867:decane; C013172:gamma-oryzanol