Enzymatic debranching of starches from different botanical sources for complex formation with stearic acid

Starches from different botanical sources (corn, potato, and tapioca) were modified enzymatically using pullulanase, and the resultant debranched starches were used to formulate inclusion complexes with stearic acid. Effects of the debranching and botanical source of starch on the degree of complex formation, thermal and crystalline characteristics of the complexes were analyzed. The amount of stearic acid in the complexes, recovered as precipitates from aqueous reaction mixtures, was high in the order of tapioca, potato and corn starches. By debranching for 12 h, tapioca starch could form the complex with stearic acid at a recovery yield of 71%, which was the maximum among the values obtained with other starches. Further, all the starch/stearic acid complexes exhibited a combination of V- and B-type polymorphs under X-ray diffraction analyses. From a thermal transition analyses, both type I and II crystals were observed in the inclusion complexes. Melting enthalpy of the inclusion complexes improved by debranching, indicating that the complexes were thermally stabilized. Overall data revealed that the enzymatic debranching of starch effectively improves the complexation, crystallinity, dispersion ability and stability of starch-stearic acid complex.