Effect of microwave-assisted dry heating with xanthan on normal and waxy corn starches

Normal corn starch (CS) and waxy corn starch (WCS) were impregnated with xanthan gum (1% based on starch) and heat-treated using a microwave in a dry state for 0, 4, or 6min (CS-X0, CS-X4, CS-X6, WCS-X0, WCS-X4, WCS-X6), respectively. Effects of the microwave-assisted dry heating (MADH) on pasting, morphological, and structural properties were evaluated. The results revealed that the viscosity of both the CS and WCS with xanthan increased compared with untreated samples after MADH, and the effect on WCS was more obvious. The syneresis values showed that the water-holding ability of CS-X6 and WCS-X6 increased, and that value of CS was lower than that of WCS after MADH with xanthan. The MADH with xanthan reduced the To, Tc, Tp, and ΔH values of both the CS and WCS. After MADH, the particle morphology of the starch-xanthan connected more densely, especially WCS, and the gelatinized samples exhibited a strong and smooth laminar structure. The Fourier transform Infrared Spectroscopy (FTIR) displayed that the absorption peak width of both CS-X6 and WCS-X6 became larger. X-ray diffraction showed that the crystallinity of CS-X6 and WCS-X6 decreased slightly as a result of MADH, and the crystalline pattern remained A-type.