Effect of debranching and heat treatments on formation and functional properties of resistant starch from high-amylose corn starches

High-amylose corn starches [(Hylon V (H5) and Hylon VII (H7)] were debranched with pullulanase, followed by autoclaving-storing cycles and drying in an oven (at 50 A degrees C) or freeze-dryer. The samples were autoclaved at 123 and 133 A degrees C and stored at 4 and 95 A degrees C. Molecular weights of the samples decreased and resistant starch (RS) contents increased with increased debranching time. RS contents of H7 samples were higher than those of H5 samples. RS contents of oven-dried samples were higher than those of freeze-dried samples. Debranching caused decreases in DSC peak temperature (T (p)) and increases in enthalpy (Delta H) values of H5 and H7. Autoclaving at 133 A degrees C caused higher Delta H values as compared to autoclaving at 123 A degrees C. The solubility and water-binding values of autoclaved-only (control) and autoclaved-debranched (3-48 h) samples and the samples treated with autoclaving-storing cycles after debranching of both H5 and H7 were higher than those of their respective native starches. Debranching of starch samples affected the emulsion capacity of albumin adversely, but improved the emulsion stability of albumin. Cold viscosity values of freeze-dried samples were higher than those of oven-dried samples. Autoclaving-storing cycles after debranching caused decreases in peak, breakdown and final viscosity values.