湿热处理对甘薯淀粉流变特性的影响

目的:采用HAAKE MARSⅢ型流变仪研究不同湿热处理条件下甘薯淀粉的流变性。方法:通过控制湿热处理的水分(10%~30%)、温度(90~130 ℃)和时间(4~12 h)对甘薯淀粉进行湿热改性。结果:原淀粉与湿热改性淀粉的糊具有明显的剪切稀化行为,其流变曲线也服从Herschel-Bulkley模型。不同湿热处理条件下得淀粉糊浓度系数K、屈服应力τ₀均低于原淀粉(K_原=14.816 Pa·sⁿ,τ_0原=10.322 Pa),流动特性指数n高于原淀粉(n_原=0.47)。随着湿热处理水分、温度与时间的增加,淀粉糊的K逐渐减小,τ₀则先增后减,湿热处理水分20%,温度110 ℃,时间8 h的屈服应力最大(τ_0上行线=5.683 Pa,τ_0下行线=12.423 Pa)。动态流变学特性表明:不论湿热改性与否,甘薯淀粉糊的储能模量(G')均大于损耗模(G″)。并且相对于原淀粉,湿热改性甘薯淀粉糊的黏弹性明显增加。结论:经过湿热处理,甘薯淀粉糊的浓度系数与屈服应力下降,非牛顿性减弱,黏弹性显著提高,更适合作为食品加工的辅料和添加剂。

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(τ0 uplink=5.683 Pa,τ0 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.