Thermal, structural and rheological properties of sorghum starch with cactus mucilage addition

Physicochemical properties including rheology of sorghum (Sorghum saccharatum) starch, with cactus (Opuntia ficus) indica mucilage addition were evaluated. Native starch and mucilage mixtures with the ratios 90:10 and 95:5 (g:g) were prepared. A significant increase in starch gelatinization temperature and enthalpy was observed with mucilage addition. Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD), revealed physical interactions between starch and mucilage, possibly by hydrogen bonds, that might restrain water mobility through the granule amorphous regions, favoring the increase in enthalpy and gelatinization temperature. Mixtures starch-mucilage, presented an increment of an amorphous disorderly state degree on starch gels. The mechanical spectra of starch gels, increased about three times the storage modulus (G′) and twice as much the loss modulus (G″), in samples with 90:10 (g:g) starch:mucilage mixture, suggesting a re-arrangement in the starch-mucilage system structure.