چکیده (انگلیسی):

The aim of this research was to describe the thermal behavior
of β-sitosterol crystals in oil-suspensions with a focus
on the role of water during heating. The suspensions
were prepared by recrystallization in order to achieve a microcrystalline
particle size. The structural changes together
with the mechanical properties of the suspensions during
heating were studied by using variable temperature X-ray
powder diffractometry (VT-XRPD), differential scanning calorimetry
(DSC), and dynamic mechanical analysis (DMA).
Hydrated β-sitosterol crystals in an oil-suspension dehydrated,
despite the composition of the suspensions, at low
temperatures. At high β-sitosterol concentration, the monohydrate
crystal form changed partially to a hemihydrated
form, and when only a small amount of water was initially
incorporated, the hemihydrate crystal form dehydrated to a
mostly anhydrate crystal form. The released water, which
was immiscible in the surrounding oil, caused the recrystallization
of hydrated β-sitosterol during cooling. This procedure
indicated a reversible dehydration process. Structural
and thermal analysis of β-sitosterol crystals in suspensions,
together with mechanical analysis made it possible to understand
various physical changes during heating.