韧化温度和时间对不同直链淀粉质量分数玉米淀粉物化性质的影响

Effect of Annealing Temperature and Time on the Physicochemical Properties of Corn Starches with Different Amylose Contents

为进一步探讨韧化处理对淀粉性质的作用机理,通过测定糊化性质、热特性、膨胀力、结晶特性及观察偏光十字现象和微观结构,研究了不同韧化温度和时间对不同直链淀粉质量分数玉米淀粉(普通玉米淀粉(normal corn starch,NCS)和蜡质玉米淀粉(waxy corn starch,WCS))物化性质的影响。结果表明,韧化处理主要作用于NCS和WCS淀粉颗粒的无定形区,对淀粉结晶类型没有影响;但韧化处理能够明显增强NCS和WCS的热稳定性和抗剪切能力,抑制淀粉老化和糊化,显著降低峰值黏度和膨胀力(P<0.05)。韧化温度升高至60 ℃时韧化效果更加明显,糊化焓和相对结晶度明显降低,颗粒表面被明显破坏。但延长韧化时间对NCS和WCS老化的抑制效果和对糊化焓、膨胀力、颗粒形貌等的影响不明显。

In order to provide useful information to explore the mechanism of the effect of annealing treatment on the physicochemical properties of corn starch, we evaluated the pasting properties, thermal properties, swelling power, crystalline structure, birefringence, and morphological structure of corn starches with different amylose contents (normal corn starch (NCS) and waxy corn starch (WCS)) annealed at different temperatures for different periods. The results showed that annealing treatment affected the amorphous zones of NCS and WCS, but exerted no effects on their crystal types. The thermal stabilities and anti-shear abilities were enhanced significantly after annealing. Annealing treatment retarded the retrogradation and gelatinization of the two starches and significantly reduced the peak viscosity and swelling power (P < 0.05). Annealing temperature up to 60 ℃ enhanced the above effects, leading to a significant decrease in the gelatinization enthalpy and the relative crystalline degree and obvious destruction of the morphological structure. However, prolonged annealing time did not significantly retard the retrogradation of NCS and WCS starches while having no significant effect on the gelatinization enthalpy, swelling power, or morphological structure.