Abstract: Response surface methodology was employed to study the reaction conditions for buckwheat resistant starch (RS) content by autoclaving enzymatic debranching recrystallization. Thermal-press temperature, pullulanase amount, pullulanase debranching time, cold preservation time at 4 ℃, were analyzed for their influence on the content of buckwheat resistant starch. A five-level-four-factor central composite design was used for maximizing the buckwheat RS content. The optimal reaction conditions obtained were thermal-press temperature 120.63 ℃, pullulanase debranching time 7.49 h, pullulanase amount 4.61 U/g, cold (4 ℃) preservation time 3.11 d, respectively. RS content experimentally obtained was 47.87%, in agreement with the predicted values. In addition, the physical shape of original starch and RS were investigated by scanning electron microscopy (SEM), the starch shape changed significantly, by rule smooth ball into larger transparent crystal structure.

Key words: buckwheat, autoclaving enzymatic debranching recrystalllization, RS, response surface methodlogy, physical shape