Functional and Pharmaceutical Properties of Physically and Chemically Modified Rice Bean (Vigna umbellata) Starches

This study explored the functional and pharmaceutical properties of native and modified starches derived from rice bean (Vigna umbellata) using physical (pregelatinization) and chemical (phosphorylation, carboxymethylation) modifications. Native starch (NRBS) exhibited a 27.5% amylose content. Modifications significantly influenced physicochemical characteristics. Swelling power increased from 12.25 g/g in NRBS to 16.34 g/g (pregelatinized, PGRBS) and 18.91 g/g (carboxymethylated, CMRBS), while solubility reached 53.12% in CMRBS. X-ray diffraction study estimated degrees of crystallinity of 26.5%, 19.4%, 22.8%, and 14.5% for NRBS, PGRBS, phosphate crosslinked (CLRBS), and CMRBS, respectively. Oil absorption capacity was highest in CMRBS (1.67 g/g), while its free swelling capacity reached 6.12 g/g at 37 °C. In vitro digestibility showed resistant starch (RS) contents of 11.31%, 5.49%, 17.38%, and 21.65% for NRBS, PGRBS, CLRBS, and CMRBS, respectively. Flowability and compressibility analysis demonstrated that CLRBS had the best flow (Carr’s Index: 12.16%, Hausner ratio: 1.14), while CMRBS exhibited superior tablet hardness across compression forces. These findings highlight rice bean starch, particularly in its modified forms, as a sustainable and multifunctional excipient and ingredient for food and pharmaceutical applications.