Effect of oxidation on physicochemical characteristics of thermoplastic canna starch

The effects of oxidation on physicochemical characteristics of thermoplastic canna starch were investigated. Thermoplastic starch (TPS) of native canna starch (CS) and oxidized canna starch (OCS) were prepared with different contents of sodium hypochlorite (1%, 3%, and 5% w/w) and 30 wt% of glycerol as plasticizer. Native starch-based TPS (NTPS) and oxidized starch-based TPS (OTPS) samples were tested for physicochemical, morphological, thermal, and mechanical properties. In OCS, the content of carboxyl and carbonyl groups increased with the increase in the content of oxidant, and this contributed to the improvement in CS plasticization efficiency. SEM images indicated that the morphology of OTPS samples was smoother than that of NTPS. The stronger interaction between OCS and plasticizer in OTPS was indicated by FTIR spectra. XRD confirmed that the crystallite type of starch was changed and their decrease in crystallinity is attributed to effects of both oxidation and plasticization. The carbonyl and carboxyl content had a large impact on T-g and Delta H-g of OTPS. The higher content of these groups in OCS leads to the lower T-g and the lower Delta H-g, which could make the plasticization easier. Due to the better plasticization in OTPS, their mechanical properties and thermal stability were enhanced.