果胶提取工艺对甜菜粕物化性质的修饰作用研究

Modification of Pectin Extraction Conditions on Physiochemical Properties of Sugar Beet Pulp

本文研究了提取溶剂对甜菜粕结构、形貌的修饰作用。甜菜粕结构致密,表面由无规则褶皱组成。经草酸铵溶液处理后(80℃,pH 5.2,浸提2遍),甜菜粕中的钙离子含量由1.28%降至0.81%,且甜菜粕具有疏松多孔状的表面形貌,但甜菜粕主要的官能团及结晶结构并未发生变化。在热酸作用下(80℃,pH 1.5),甜菜粕中的原果胶逐渐转化为可溶性果胶;此时,甜菜粕的光谱信息也发生相应的变化,表现为2930 cm-1的红外光谱吸收峰变强、相对结晶度增加。溶解于草酸铵的甜菜果胶得率为2.6%,而酸溶性甜菜果胶得率中为13.1%;所有甜菜果胶提取物均富含半乳糖醛酸、中性糖。研究结果表明,草酸铵能解除钙离子对部分甜菜果胶的束缚,并降低甜菜粕的致密度;稀酸对甜菜粕具有强修饰作用,不仅能溶解甜菜果胶及细胞壁中的钙离子,还能显著提高甜菜粕的相对结晶度。

The modification of extractant type on the structure and morphology of sugar beet pectin was studied in this study. Sugar beet pectin showed a compact texture and the appearance was made up of irregularly folding architecture. After treatment with the oxalate ammonia （80 ℃, pH 5.2, twice）, the calcium content in the sugar beet pulp decreased from 1.28% to 0.81%; the morphology of the sugar beet pulp changed into a highly loose and polyporous texture., while the major functional groups and the crystallinity of the sugar beet pulp did not change. After the heat-acid treatment （80 ℃, pH 1.5）, the protopectin located in the pulp was gradually converted into soluble pectin. Meanwhile, the spectroscopic characteristics of FTIR and XRD changed accordingly; the absorption band of FTIR at 2930 cm-1 became stronger and the relative crystallinity increased to a higher level. The Yield of the pectins solubilized in oxalate ammonia was 2.6%, while that of the acid-soluble pectin reached to 13.1%. All pectin extracts were predominantly comprised of galacturonic acid and neutral sugars. The results obtained in this work showed that oxalate ammonia liberated some pectins from the cell wall by chelating intrinsic calcium ions, and decreased the compactness of the sugar beet pulp. The dilute acid leaded to a significant modification effect on the pulp because it not only solubilized both sugar beet pectins and calcium ions presented in the cell wall, but also improved significantly the relative crystallinity of the sugar beet pulp.