不同加热-冻融循环处理对甘薯淀粉结构及物化特性的影响

Effect of Gelatinization and Retrogradation Cycle Treatments on the Structure and Physicochemical Properties of Sweet Potato Starch

本文研究了不同温度下(75、95和121℃)重复的加热-冻融循环处理对甘薯淀粉结构及物化特性的影响。采用扫描电子显微镜、X-射线衍射、差示量热扫描仪及快速黏度测定仪对甘薯淀粉的结构、结晶性质、热特性和糊化特性进行分析,并测定了其膨胀势、溶解度和体外消化性。75、95和121℃加热-冻融循环处理均使甘薯淀粉颗粒形态破坏或消失,呈不规则块状;75℃加热-冻融循环处理导致了甘薯淀粉结晶吸收峰及热吸收峰强度减弱,焓值降低、糊化温度升高且范围变小,而经95和121℃加热-冻融循环处理后,甘薯淀粉结晶型由A型向B型转化,热吸收峰消失;此外,甘薯淀粉溶解度随着加热-冻融循环次数的增加呈先降低后增加的趋势,各黏度特征值降低,回生趋势减弱,慢速消化淀粉(SDS)含量有所增加,121℃一次加热-冻融循环处理(RGR-1)后含量最高,可达29.25%。

The effects of different repeated gelatinization and retrogradation (RGR) treatments at temperatures of 75, 95, and 121 on the structural and physicochemical properties of sweet potato starch were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and rapid visco analysis (RVA) were used to evaluate the changes in the structural, crystalline, thermal, and pasting properties of sweet potato starch. The swelling power, solubility, and in vitro digestibility were also determined. The starch granule morphology was damaged or disappeared and irregular lumps formed after RGR treatment at 75, 95, or 121. For the RGR cycle treatment at 75, the intensities of the crystal absorption peak and heat absorption peak of sweet potato starch were reduced, while its gelatinization enthalpy decreased. The gelatinization temperature increased and the gelatinization temperature range became smaller. After RGR cycle treatments at 95 and 121, the X-ray diffraction patterns of sweet potato starch were converted from A-type to B-type and the heat absorption peak disappeared completely. In addition, with the increasing RGR cycles at different temperatures, the solubility of sweet potato starch increased first and then decreased, resulting in a decrease of starch viscosity characteristic value, a weakening retrogradation trend, and an increase of the slowly digestible starch (SDS) content. The highest SDS content (29.25%) of sweet potato starch was found in one RGR cycle treatment (RGR-1) at 121. © 2015, Editorial Board of Modern Food Science and Technology. All right reserved.