苹果酸玉米淀粉酯理化性质及消化特性研究

Physicochemical Properties and Digestibility of Malate Corn Starch

苹果酸玉米淀粉酯是L-苹果酸(有机酸)和玉米淀粉在一定条件下反应生成的一种酯化变性淀粉,具有与膳食纤维相似的功能特性。以L-苹果酸和玉米淀粉为原料在高温下干热处理制备苹果酸淀粉酯,旨在阐明苹果酸淀粉酯表观结构、糊化特性、溶胀特性以及体外消化特性等物理化学特性与玉米原淀粉的差异;明晰不同取代度的淀粉酯在表观结构和理化特性方面的变化,并通过X-射线衍射(XRD)、扫描电子显微镜(SEM)和傅立叶红外光谱(FT-IR)进行分析。结果表明:苹果酸淀粉酯的白度、溶胀度、冻融稳定性、糊化特性较原淀粉下降;扫描电镜图中可以观察到低取代度的淀粉酯中出现较多小颗粒的淀粉碎片,随着取代度增加,淀粉表面粗糙且出现小孔,颗粒形状不规则,碎片之间发生明显的粘连;原淀粉与低取代度的苹果酸淀粉酯的X-射线衍射图表现为A型结晶,但随着取代度增大,结晶结构被破坏,衍射峰变弱且最终消失。红外光谱结果表明:酯化后的淀粉均在1739cm-1处出现了羰基振动的特征峰,且随着取代度增加峰值明显。体外消化试验结果表明:经酯化后的淀粉,抗性淀粉含量明显增加。

Malate corn starch is one kind of modified starch by the esterification of malic acid(organic acid)with corn starch,which has some similar functional characteristics of dietary fiber.In this study,L-malic acid and corn starch were used as raw materials to prepare malate starch by the dry heat treatment at high temperature.This work aims to elucidate the differences between the physicochemical characteristics of malate starch and corn starch,such as its apparent structure,gelatinization,swelling and in vitro digestibility characteristics.The changes of apparent structure and physicochemical properties of malate starch with different degrees of substitution were clarified,and the samples were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM)and infra-red spectroscopy(FT-IR).The results showed that,compared with the corn starch,the whiteness,swelling,freeze-thaw stability and gelatinization of malate starch decreased.In SEM,more small starch fragments were observed in the malate starch with low degree of substitution.With the increase of the degree of substitution,the surface of starch became rough and holes appeared,and the particle shape became irregular,finally the adhesion between fragments was observed.The X-ray diffraction pattern of the corn starch and the malate starch with low degree of substitution showed that the crystal was A-type crystal.However,as the degree of substitution increased,the crystal structure was destroyed,and the diffraction peak became weaker and finally disappeared.The results of FT-IR indicated that the characteristic peak of carbonyl vibration appeared in the esterified starch at 1 739 cm-1,and the peak value increased obviously with the increase of the degree of substitution.In vitro digestion experiment showed that the content of resistant starch increased obviously after the esterification.