Semi-Dry Impregnation Method Of Rice Starch With Xanthan Gum Prior To Modification By Dry Heat Treatment

Dry heated xanthan gum-rice starch samples were prepared by dry heat treatment (130 degrees C) of high, medium and low amylose rice starches (HA, MA and LA, respectively) with xanthan gum (X) using semi-dry impregnation method (SD) (modified samples: HAX-SD-130, MAX-SD-130, LAX-SD-130). Interactions between starch molecules and xanthan gum induced by dry heat treatments were revealed as xanthan gum was anchored to swollen granules and not dispersed upon cooking. No breakdown viscosity was observed for HAX-SD-130 and MAX-SD-130 during pasting. Paste clarity of modified samples was not detected due to restricted swelling of starch granules. Storage modulus (G') of modified samples at 95 degrees C and 25 degrees C was increased. Gelatinization and retrogradation temperatures of modified samples slightly changed while gelatinization enthalpy (Delta H) of modified samples generally decreased. Dry heat treatment with xanthan gum generally tended to inhibit the retrogradation of rice starches. Modified samples prepared by semi-dry impregnation method showed improved paste stability under prolonged cooking time (95 degrees C, 10 min) or acidic condition (pH = 3).