不同提取方法对黄秋葵果胶含量和结构特性的影响

Effects of Different Extraction Methods on the Content and Structural Properties of Pectin from Okra

本研究探讨了酸水热提、酶解、超声及酶解-超声四种提取方法对黄秋葵果胶含量及其结构特性的影响。酸水热提及酶解-超声联合法对黄秋葵果胶提取效果优于酶解和超声法;当干秋葵加入20倍pH 3 HCl水溶液,以70℃浸提1h(酸水热提法)或添加3‰果胶酶、50℃酶解90min后置于200W超声波处理10min(酶解-超声法)时,其果胶平均含量(以半乳糖醛酸质量分数计)达到43.61g/kg及32.59g/kg。四种提取方法所制果胶均为吡喃糖构型,但酸水热提及酶解法制备果胶的酯键易发生降解,其在1725cm^(-1)红外吸收峰有变弱甚至消失趋势;而超声或酶解-超声法处理则促进了果胶分子链断裂,其平均分子量由酸水热提法下533ku分别降至420～467ku、319ku。研究结果表明:采用酸水热提法(pH 3、70℃)制备黄秋葵果胶,其果胶得率高、分子量分布集中、外观呈片状且排列致密。本研究结果为高品质秋葵果胶的制备奠定基础。

The effects of four extraction methods such as hot acid-water extraction,enzymolysis,ultrasound,and enzymolysis-ultrasound treatment on the content and structural characteristics of the pectins from okra were studied,and the hot acid-water extraction and enzymolysis-ultrasound methods were found more effective.At the ratio of dried okra to the HCl aqueous solution(pH 3)of 1:20,the extraction at 70℃for 1 h(the hot acid-water extraction method)or with addition of 3‰of pectinase,and the digestion at 50℃for 90 min followed by an ultrasound treatment at 200 W for 10 min(the enzymolysis-ultrasound method),led to a pectin content(as the galacturonic acid mass in okra)of 43.61 and 32.59 g/kg,respectively.All the pectins produced by the four extraction methods was in the pyranose configuration,but the ester bond in the pectins prepared via the hot acid-water extraction or the enzymolysis method tended to degrade,causing the infra-red adsorption peak at 1725 cm-1 to be weakened or even disappear.Whereas,the ultrasound methods or enzymolysis-ultrasound treatment promoted the breakage of the pectin molecular chain,making its average molecular weight decrease from 533 ku(by the hot acid-water method)to 420~467 ku and 319 ku.The results showed that the okra pectin prepared via the hot acid-water extraction method had a higher extraction yield and narrow molecular weight distribution with a flake-like and densely arranged appearance.The results of this research has laid the foundation for the preparation of high quality okra pectin.