Formation of Resistant Starch in Corn Starch and Estimation of its Content from Physicochemical Properties

The effect of autoclaving temperatures (100-120 degrees C) on yields of enzyme-resistant starch (RS) from normal corn starch and the physicochemical properties of autoclaved-cooled starches were studied. The RS content increased linearly with increasing autoclaving temperature (R-2 = 0.993) and the number of autoclaving-cooling cycles at an autoclaving temperature of 120 degrees C. The effect of the number of autoclaving-cooling cycles was more pronounced than that of temperature. The swollen starch weight measured at 60 degrees C slightly increased as the RS content increased, and then drastically decreased with the continous increase of the RS content (R-2 = -0.969). As the RS content increased, all parameters of Rapid Visco Analyser (RVA) viscosity except breakdown decreased. Log RVA peak viscosity showed a negative correlation with the RS content (R-2 = -0.986). The enthalpy in the differential scanning calorimetry (DSC) endotherm corresponding to the transitions of RS linearly increased as the RS content increased (R-2 = 0.988). The RS content of the heat-treated starch estimated from the relationship between RS content and swollen starch weight at 60 degrees C, log RVA peak viscosity or DSC enthalpy was in good agreement with that determined with the standard method.