Microencapsulation of Rosemary Essential Oil by Co-Extrusion/Gelling Using Alginate as a Wall Material

An essential oil is the volatile lipophilic component extracted from plants. Microencapsulation systems protect the essential oil from degradation and evaporation, and at the same time allow a sustained release. This work analyzed and characterized the rosemary essential oil microcapsules prepared by co-extrusion technique using alginate as wall material and calcium chloride as cross linker. Several instrumental techniques were used: optical microscopy, coulter counter, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), termogravimetric analysis (TGA), spectrophotometry, antimicrobial test and chromatography. Results show that rosemary oil has pesticidal properties, and its microencapsulation allows knowing that these properties remain inside the microcapsules.

钙离子存在下海藻酸盐稀溶液的粘度性质

通过测定体系的粘度,研究了加入不同量的Ca2+到海藻酸钠稀溶液中所引起体系粘度的变化规律。考察了海藻酸钠浓度、温度、以及外加NaC l对粘度的影响。结果表明,在较高浓度(质量分数分别为0.125%和0.15%)时,随着Ca2+加入量的增大,海藻酸盐体系的粘度先降至一极小值,然后迅速增大,直至有凝胶状物质生成;在较低浓度(质量分数为0.075%)时,海藻酸盐体系的粘度则变化幅度不大;在15~35℃温度范围内,Inηrel-1/T具有良好的线性关系;NaC l的加入使体系相对粘度下降。FTIR和DSC结果表明,Ca2+与海藻酸盐发生了相互作用,所形成的海藻酸钙复合物的热稳定性比相应的海藻酸钠高。

pH值对海藻酸钠溶液黏度及体系中氢键的影响规律

为了分析不同pH值下海藻酸钠(SA)溶液黏度的变化规律及其形成机制,首先测试了不同pH值下SA溶液的流变曲线,采用高斯分峰拟合法对各SA溶液的FTIR谱图中羟基的特征吸收峰进了分峰拟合,并根据拟合结果统计了各SA溶液体系中氢键的类型和相对强度。同时研究了储存时间对不同pH值SA溶液的黏度和体系中氢键强度的影响。结果表明,不同pH值下SA溶液均呈现剪切变稀的特性,且随着pH值的增大,SA溶液的黏度下降;各SA溶液体系中存在分子间和分子内氢键,SA溶液中分子间氢键的相对强度随着pH值的增大而降低,同时SA表面的负电荷增加,使得SA分子之间的静电斥力增加,导致黏度下降。冷藏储存24 h后,pH值为5和9的SA溶液体系中分子间氢键的相对强度分别增加4. 22%和20. 13%,导致SA溶液的黏度增大;而pH值为7的SA溶液体系中分子间氢键的相对强度仅增加0. 29%,其溶液的黏度几乎没变。