超声辅助酶法降解枳实果胶及其衍生物抗氧化性能

Ultrasound-assisted enzymatic degradation to obtain pectin derivatives from Citrus aurantium L.and its antioxidant properties

采用超声辅助酶法对枳实果胶进行降解,获得枳实果胶降解衍生物。以抗氧化活性为指标,考察了超声预处理时间、酶种类、酶添加量等因素对枳实果胶降解衍生物抗氧化活性的影响。利用滴定法、凝胶色谱法和红外光谱等技术分析了枳实果胶降解衍生物中半乳糖醛酸含量、分子量分布以及结构特性,以验证果胶降解衍生物抗氧化构效关系。结果表明:当果胶酶作为降解酶,酶用量为6000 U/g,超声预处理时间为20 min时,制备的枳实果胶降解衍生物的抗氧化活性最佳,此条件下其质量浓度为3 mg/mL时,对DPPH自由基的清除率为62.94%,对ABTS自由基的清除率为52.67%,还原能力为0.9627,与未降解的枳实果胶相比,抗氧化活性显著提高。枳实果胶降解衍生物中半乳糖醛酸含量随降解工艺的不同存在明显差异,且半乳糖醛酸含量与抗氧化活性呈正相关。此外,枳实果胶降解衍生物分子量更低,且甲氧基含量也明显降低,但降解过程并没有改变果胶的吡喃糖结构。研究结果为枳实果胶的高值化利用提供理论依据和参考。

In this paper,pectin derivatives obtained from the degradation of Citrus aurantium L.pectin was prepared by ultrasound-assisted enzymatic method.The effects of ultrasound pretreatment time,enzyme type and amount of enzyme addition on the antioxidant activity of degradation derivatives of Citrus aurantium L.pectin were investigated.Then the content,molecular weight distribution and structural properties of galacturonic acid from the degradation derivatives of Citrus aurantium L.pectin were analyzed by titration gel chromatography and infrared spectroscopy to verify the plausible explanation for the enhanced antioxidant activity of pectin degradation derivatives.The results confirm that the best scavenging rate of DPPH radicals and ABTS radicals as well as the reducing ability of potassium ferricyanide of the pectin degradation derivatives are obtained,when pectinase is selected as the degrading enzyme with the dosage of 6000 U/g and the ultrasound-pretreatment time is 20 min.Under these conditions,the degradation derivatives of Citrus aurantium L.pectin prepared at a mass concentration of 3 mg/mL,shows a more significant increasing in antioxidant activity with a 62.94%scavenging of DPPH radicals,a 52.67%scavenging of ABTS radicals and a reducing capacity of 0.9627,compared to the undegraded pectin.The content of galacturonic acid in the degradation derivatives of Citrus aurantium L.pectin varies significantly with the degradation process.Also it is verified that it is a positive correlation between galacturonic acid content and antioxidant activity,and that a lower molecular weight and lower methoxy content of the degradation derivatives are obtained compared to Citrus aurantium L.pectin,but the pyranose structure of the pectin is not changed in the degradation process.The results of this study provide theoretical basis and reference for the highvalue utilization of Citrus aurantium L.pectin.