CP/MAS 13C NMR技术分析酸提取对烟草果胶产率和结构的影响

摘要

In order to investigate the fine structure of tobacco pectin and the key factors in extraction, the effects of extraction conditions (including pH, temperature and extraction time) on the yield, purity and structure of pectin were studied by cross-polarization/magic angle spinning 13C nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. The results showed that: 1) The highest pectin yield (10.87%) achieved after extracting for 1.5 hours at pH 1.5 and 85 ℃; while polygalacturonic acid(PGA)reached its highest purity (78.4%) after extracting for 1.5 hours at pH 2.0 and 95 ℃. 2) The extraction conditions influenced the structure of pectin to a certain extent, the degrees of methylation (DM) and acetylation (DA) of pectin increased as pH value increased from 1.5 to 2.5, while decreased with the rise of temperature and the prolongation of extraction time significantly.%为研究烟草果胶的精细结构和掌握果胶提取的关键因素，采用交叉极化/魔角旋转固态核磁光谱技术（CP/MAS 13C NMR）考察了酸提取条件（pH、温度和提取时间）对烟草果胶产率、纯度（质量分数）及结构的影响。结果表明：①在pH 1.5和85℃条件下提取1.5 h时，烟草果胶得率最高，为10.87%，但在pH 2.0和95℃条件下提取1.5 h时，聚半乳糖醛酸（PGA）的纯度最高，为78.4%。②提取条件对烟草果胶的结构也有一定的影响，pH=1.5~2.5时，果胶的甲酯度（DM）和乙酰度（DA）均随pH升高而增大，随温度升高而降低，随提取时间延长而显著下降。