The combined effect of thermal-acid hydrolysis, periodate oxidation, and iodine species removal on the properties of native tapioca (Manihot esculenta Crantz) starch

Through a four-step top-down approach, native tapioca starch (NTS) was thermally acid-hydrolyzed, periodate-oxidized with subsequent removal of iodine species (i.e., IO4(−), IO3(−), I(−), and I2), and dialdehyde tapioca starch (DTS) alcohol-precipitation. The percent yield was ∼91%. Analyses confirmed the presence of aldehydic functionalities (∼71%), effectual iodine species removal (∼98%), and enhanced water-solubility (∼96.57%). Besides, the combined treatment significantly reduced the Mw (∼57.81 kDa) and ameliorated homogeneity as well as thermal stability (Tmax ∼ 667.15 °C). Structural-spectral characterization also confirmed the presence of aldehydic functionality, polymorphic transition (C- to A-type), and a higher degree of crystallinity (∼91.77%), the latter further corroborated by thermal analysis. The morphological study revealed that the combined treatment reduced size (∼393.55-nm-diameter and ∼5.22-μm-length) and changed shape into rod-like crystals. DTS showed considerably and significantly low cytotoxicity to HaCaT cells in vitro at the concentrations assayed over the test period (24 h). DTS's conformation was most stable at −289 kcal/mol and −151.7 au heat formation and minimum potential energies, respectively. Overall, these results demonstrated that the combined treatment had no deleterious effects on NTS's properties, thus yielded DTS with ideal properties for multifarious uses. •Treatment yielded DTS with ∼71% aldehyde content, ∼96.57% water-solubility, < 2% iodine species, and low cytotoxicity.•The combined effect reduced Mw / size and, conversely, increased homogeneity, reactivity, crystallinity, and heat-stability.•Treatment induced a polymorphic transition from C- to A-type and truncated-rounded granules to rod-like crystal structures.•Combined treatment had no adverse effects on properties, and DTS could potentially be used for biomaterial applications.