Physicochemical, Thermal, Pasting and Microstructure Properties of Hydroxypropylated Jackfruit Seed Starch Prepared by Etherification with Propylene Oxide

The jackfruit seed starch was subjected to the hydroxypropylation process by using various volumes of propylene oxide in the range of 5-50 ml (HP5-HP50). It was found that the molecular substitution (MS) increased with the volume of propylene oxide used. The shape of the native starch appeared irregular, round to bell or semi-oval with an average size of 7.66 mu m. The modified granules were still intact in granular form without fragmentation. However, the presence of traces of degradation was observed on some starch granules, particularly the treatment of HP40-HP50. No marked differences in the XRD pattern were observed between the native starch and the hydroxypropyl derivatives. However, a decrease in the degree of crystallinity was found as the volume of propylene oxide in the reaction mixture increased. The swelling power and solubility of the hydroxypropylated starches were higher than in the native starch. Progressive increases in swelling power and solubility were observed as the MS increased among the hydroxypropylated starches. The pasting properties revealed that decreases in the pasting temperature, final viscosity and setback was found with increasing MS while the breakdown increased. Hydroxypropylated starches had lower gelatinization parameters (To, Tp, Tc and Delta H) compared with the native starch. During refrigerated storage of the starch gel, the native starch showed syneresis from the first cycle while no syneresis was found during seven cycles for the treatment of HP10-HP50.