Effects of Heat-moisture Treatment on Rheological Properties of Sweet Potato Starch

Objective:Using HAAKE MARS Ⅲ rheometer to study the rheological properties of sweet potato starch under different heat-moisture treatments(HMT). Methods:Sweet potato starch was heat-moisture treatment modified by controlling moisture contents(10%~30%),temperature(90~130 ℃)and time(4~12 h). Result:The paste of sweet potato starch and moist heat modified starch had obvious shear thinning behaviors,and its rheological curve also obeyed Herschel-Bulkley model. The concentration coefficient K and yield stress τ₀ of starch paste obtained under different heat-moisture treatment conditions were lower than those of native sweet potato starch(K=14.816 Pa·sⁿ,τ₀=10.322 Pa),and the flow characteristic index n was higher than that of Native sweet potato starch(n=0.47). With the increasing of heat-moisture treatment moisture,temperature and time,K of starch paste decreases gradually,while τ₀ increased first and then decreased. When heat-moisture treatment moisture contents was 20%,the temperature was 110 ℃,and the time was 8 h,the maximum yield stress(τ_{0 uplink}=5.683 Pa,τ_{0 downlink}=12.423 Pa). The dynamic rheological properties test showed that the storage modulus(G')of sweet potato starch paste was greater than the loss modulus(G″),whether HMT or not. Compared with sweet potato starch,the viscoelasticity of sweet potato starch paste modified by HMT increased significantly. Conclusion:The concentration coefficient and yield stress of sweet potato starch paste decreased,the non-Newtonian properties decreased and the viscoelasticity increased significantly after HMT. It would be more suitable for food processing aids and additives.