Effects of hydroxypropylation on the functional properties of psyllium

The hydroxypropylated psyllium derivatives were successfully prepared with propylene oxide under the alkaline condition for the first time. Four hydroxypropylated psyllium derivatives, denoted as HP1, HP2, HP3, and HP4, were characterized for their hydroxypropyl content, molar substitution, and IR spectra. The hydroxypropyl derivatives were also evaluated for their surface structure, gelling properties, water uptake capacities, swelling volumes, and in vitro bile acid-binding abilities. The results showed that hydroxypropylation significantly reduced the gelling properties of psyllium. Psyllium derivatives with a relatively low hydroxypropyl substitution degree had greater in vitro binding capacities against cholic and chenodeoxycholic acids and higher swelling ability. The results from this study suggested that hydroxypropylation may be a possible approach for obtaining novel psyllium derivatives with improved physicochemical, functional, and biological properties for utilization in functional foods or supplemental and pharmaceutical products.