红豆淀粉-脂质复合物结构及体外消化性质

Structure and in Vitro Digestibility of Adzuki Bean(Vigna angularis) Starch-Lipid Complexes

将红豆淀粉与棕榈酸、硬脂酸、油酸和亚油酸4种脂肪酸复合,采用微波处理淀粉后,使用水浴加热方法制备红豆淀粉-脂质复合物,利用扫描电子显微镜、差示扫描量热仪、傅里叶变换红外光谱及X射线衍射探讨复合物的结构变化,并测定复合物的体外消化特性。结果表明,在扫描电子显微镜下观察,与对照红豆淀粉相比,红豆淀粉-脂质复合物的体积增大,表面凹凸不平。差示扫描量热分析结果表明红豆淀粉只有单一峰,而复合物有3个峰,证明复合物是由Ⅰ型和Ⅱ型复合物共同构成;糊化起始温度、峰值温度、结束温度均升高,说明加入脂肪酸抑制了淀粉的糊化;热焓随着脂肪酸碳链长度及不饱和度的增加而增大,热焓的增加可能与抗性淀粉的形成有关。傅里叶变换红外光谱分析结果表明复合物形成,氢键的增加可能使抗性淀粉含量增多。复合物产生了Ⅴ型结晶结构的衍射角,晶体特性发生改变,证明了复合物的存在,添加棕榈酸、硬脂酸、油酸形成复合物的特征峰强度明显高于添加亚油酸形成复合物的特征峰强度,随着Ⅴ型特征峰强度的增加,抗性淀粉含量增多。复合物的快速消化淀粉质量分数降低、缓慢消化淀粉及抗性淀粉质量分数升高,抗消化性随着脂肪酸碳链长度的增加及不饱和度的增加而降低。4种脂肪酸对红豆淀粉结构及体外消化影响不同,其中,以棕榈酸的影响效果最为显著。本实验可为淀粉-脂质复合物的结构性质及其在抗性淀粉的应用提供参考依据。

Adzuki bean starch was complexed with four fatty acids(palmitic, stearic, oleic and linoleic acid), separately. After microwave-assisted pretreatment of the starch, starch-lipid complexes were prepared by water bath heating. The structures of the starch-lipid complexes were investigated by scanning electron microscopy(SEM), differential scanning calorimetry(DSC), Fourier transform infrared(FT-IR) spectroscopy and X-ray diffraction(XRD). Their digestion characteristics in vitro were determined as well. The results showed that the volume of the four complexes, with uneven surfaces, increased when compared with the control starch under SEM. DSC analysis indicated that there was only one single peak in rice bean starch but three in each of these complexes, suggesting that the complexes were composed of type Ⅰ and type Ⅱ complexes. Gelatinization onset temperature, peak temperature, and conclusion temperature increased in the four complexes, which confirmed that the addition of fatty acids inhibited the gelatinization of the starch. Thermal enthalpy increased with the increase in the carbon chain length or the degree of unsaturation of fatty acids. The increase in enthalpy value was possibly related to the formation of resistant starch. FT-IR spectroscopy demonstrated the formation of complexes. Increased number of hydrogen bonds may increase the content of resistant starch. The complexes generated a diffraction angle of the Ⅴ-type crystal structure accompanied by changes in crystal characteristics, which proved the existence of the complexes. The characteristic peak intensity of the complexes with palmitic, stearic or oleic acid was significantly higher than that of the complex with linoleic acid. As the intensity of the Ⅴ-shaped characteristic peak increased, the resistant starch content increased. The relative content of rapidly digested starch in all complexes decreased, the relative contents of slowly digested starch and resistant starch increased, and the anti-digestibility of the starch decreased with the increase in the carbon chain length or unsaturation degree of fatty acids. The four fatty acids had different effects on the structure and in vitro digestion of adzuki bean starch. Among them, palmitic acid had the most significant effect. This study could provide useful information for further studies on the structural properties of starch-lipid complexes and their applications in resistant starch.