Guo Xiujun, Duan Hanying, Wang Chao, Huang Xuesong
Department of Food Science and Engineering, Jinan University , Guangzhou 510632, China.
J Agric Food Chem. 2014 Jul 9;62(27):6354-61. doi: 10.1021/jf5004545. Epub 2014 Jun 27.
Calcium pectinate (CaP) was prepared from citrus pectin using either calcium chloride (C-CaP) or calcium hydroxide (HO-CaP) as the source of calcium for the reaction. The production yields and the rates of decalcification for the two calcium pectinates were compared and both found to be lower for C-CaP than for HO-CaP. In an attempt to explain these differences, certain chemical and structural characteristics of the two products, including functional groups (-CH3, C═O, COO-), rheological properties, morphology, and egg-box junction zones, were investigated by Fourier transformation infrared (FTIR) spectroscopy, rheology, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results from FTIR showed that, with an increase in calcium content, the wavenumber values and peak areas of FTIR for -CH3, C═O, and COO- groups all changed dramatically for C-CaP, while they were virtually unchanged for HO-CaP. Rheological analysis of the CaP gel showed that C-CaP had a stronger cross-linked network structure and a greater range of elastic behavior as compared to HO-CaP. SEM images of two CaP gels showed irregular membranes. C-CaP maintained a tight structure and a smooth surface, whereas HO-CaP was loose and rough. The results from XRD revealed a higher degree of crystallinity within C-CaP than within HO-CaP, which indicated that C-CaP possessed compact, ordered, and stable egg-box junction zones while the junction zones in HO-CaP were metastable and loose.
以氯化钙（C-CaP）或氢氧化钙（HO-CaP）作为反应的钙源，从柑橘果胶中制备了果胶酸钙（CaP）。比较了两种果胶酸钙的产率和脱钙速率，发现C-CaP的这两项指标均低于HO-CaP。为了解释这些差异，通过傅里叶变换红外光谱（FTIR）、流变学、扫描电子显微镜（SEM）和X射线衍射（XRD）研究了两种产物的某些化学和结构特征，包括官能团（-CH3、C═O、COO-）、流变性质、形态以及蛋盒连接区。FTIR结果表明，随着钙含量的增加，C-CaP中-CH3、C═O和COO-基团的FTIR波数值和峰面积均发生显著变化，而HO-CaP的这些值几乎不变。对CaP凝胶的流变学分析表明，与HO-CaP相比，C-CaP具有更强的交联网络结构和更大范围的弹性行为。两种CaP凝胶的SEM图像显示出不规则的膜。C-CaP保持紧密的结构和光滑的表面，而HO-CaP则疏松且粗糙。XRD结果表明，C-CaP的结晶度高于HO-CaP，这表明C-CaP具有紧密、有序且稳定的蛋盒连接区，而HO-CaP中的连接区是亚稳态且疏松的。
