Brazilian Amazon white yam (Dioscorea sp.) starch

the functional properties of starch granules define its application in food and non-food industries. thus, in this study we investigated thermal, rheological, structural and colour properties of the native and modified starch of the amazon dioscorea sp. (white yam) tuber. the dioscorea sp. native starch was modified by applying single, simultaneous and combined modification agents (sodium hypochlorite, ultraviolet (uv) radiation and microwave irradiation). the thermogravimetric curves showed three main mass losses and increased thermal stability for the triple (naclo + uv + microwaves) modified sample. the uv-irradiated samples required less energy (enthalpy) to gelatinize as registered by the differential scanning calorimetry. performing modification using microwaves resulted in starches of highly viscous pastes as recorded by the rapid visco analyser. all the starch gel samples presented thixotropic behaviour, in which pseudoplastic characteristics were adequately described by ostwald–de waele and herschel–bulkley models. rheological evaluation also revealed that one-step modified starches could produce stronger gels than the native one. lower degree of relative crystallinity and a wide range of granule sizes were demonstrated by x-ray diffraction patterns and scanning electron microscopy. the colour measurement revealed the brightening and browning action of naclo and microwaves, respectively.