Thermal gelation of aqueous curdlan suspension: preparation of curdlan jelly.
Curdlan jelly was prepared by heating an aqueous curdlan suspension at 70 degrees C for 5 min. Theophylline, as a model drug, was entrapped in the jelly network. Curdlan jelly had a hardness comparable with that of commercially available jelly for confectionary. Syneresis was observed for 8 days after the preparation and was not detected during the experimental term from the gel prepared from 10% w/v curdlan suspension. Release of theophylline from the jellies was sustained, and was increasingly delayed with an increase in the curdlan concentration. An aqueous curdlan suspension was studied by means of differential scanning calorimetry (DSC) up to 80 degrees C and down to -25 degrees C, and subsequent re-heating to 30 degrees C. Enthalpy increased with the concentration of curdlan, while the temperature at the onset of the endothermic peak decreased with the concentration of curdlan. The enthalpy due to thermal gelation of 1 mg curdlan was 12.2 mJ. An increase in curdlan concentration decreased the enthalpy and lowered the onset temperature of the endothermic peak during the DSC re-heating scan. The results are due to an increase in the amount of non-freezing water and freezing bound water and a decrease in free water. The number of water molecules entrapped in the curdlan jelly as non-freezing water was 8.1 per glucopyranose residue.
Hino
Tomoaki
T
Faculty of Pharmaceutical Sciences, The University of Tokushima, Sho-machi 1-78-1, Tokushima 770-8505, Japan. hino@ph.tokushima-u.ac.jp
Ishimoto
Hayato
H
Shimabayashi
Saburo
S
D002151:Calorimetry; D002626:Chemistry, Pharmaceutical; D003692:Delayed-Action Preparations; D005936:Glucans / Q000737:chemistry*; D006801:Humans; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D013535:Suspensions; D013806:Theophylline / Q000737:chemistry; D047071:beta-Glucans
D003692:Delayed-Action Preparations; D005936:Glucans; D011135:Polysaccharides, Bacterial; D013535:Suspensions; D047071:beta-Glucans; C038459:curdlan; D013806:Theophylline