木薯双醛淀粉的理化性质

Physicochemical Properties of Cassava Dialdehyde Starch

使用高碘酸钠氧化木薯淀粉制备了醛基含量5%~85%的双醛淀粉(DAS-5~DAS-85),利用FT-IR、凝胶渗透色谱(GPC)、X射线衍射(XRD)、偏光显微镜、扫描电镜(SEM)研究了双醛淀粉的结构和性质,结果显示:木薯淀粉分子量高于1000万,醛基含量为5%时淀粉重均分子量降为9300。氧化反应首先发生在淀粉非晶区,而后破坏结晶区,醛基含量高于39%时淀粉变为无定型结构。随醛基含量增加,双醛淀粉糊化温度升高,糊化焓减小,颗粒表面变粗糙,结构塌陷。在25℃下,质量分数为10%的DAS-85溶液放置6 h出现透明沉淀,DAS-53溶液放置12 h出现透明沉淀,DAS-39溶液48 h后仍澄清。

Dialdehyde starch was prepared by the oxidation of cassava starch with sodium periodate,whose aldehyde contents were 5%to 85%.The influences of oxidation degree of dialdehyde starch on the structures and properties were investigated by FT-IR,gel permeation chromatography(GPC),X-Ray diffractomer(XRD),polarization microscopy and scanning electron microscopy(SEM).GPC results showed that molecular weight of cassava starch was more than ten million,while dialdehyde starch with 5%degree of oxidation had a mass average molecular weight of 9300.XRD patterns indicated the crystallinity decreased with increasing content of the aldehyde groups and it became amorphous when aldehyde content exceeded 39%.Polarization microscopy images showed the oxidation reaction first occurred in the amorphous area and then destroyed the crystalline region.SEM images showed the surface of dialdehyde starch granules became wrinkled.Gelatinization peak temperature increased and enthalpy decreased with increasing content of aldehyde groups.Transparent precipitation formed in DAS-85 solution with 10%mass concentration after 6 h and occurred in DAS-53 solution after 12 h at 25℃.DAS-39 solution remained transparent after 48 h at 25℃.