柑橘果肉果胶的流变和结构特性

摘要

以柑橘果肉为原料,采用稀酸提醇沉法提取果胶粗品,研究了果胶溶液的浓度及热处理温度对果胶溶液流变学性质的影响。采用DEAE Cellulose-52柱对柑橘果肉粗品进行洗脱得到3个多糖组分(P-0, P-1和P-2),对其分子量、半乳糖醛酸、单糖组成及酯化度等进行分析,并利用红外光谱及核磁共振氢谱等对各组分进行结构特性分析。结果表明,柑橘果肉果胶为典型的剪切稀化型非牛顿流体； P-0, P-1和P-2组分分子量存在显著差异；柑橘果肉果胶为富含糖醛酸的酸性多糖,且是发生部分乙酰化的低酯果胶,其单糖组成以半乳糖醛酸、半乳糖、阿拉伯糖、鼠李糖和岩藻糖居多,且均以Ⅰ型聚鼠李半乳糖醛酸( RG-Ⅰ型)结构为主；3种组分糖环类型均是吡喃糖,糖苷键既有α型,又有β型。%Raw pectin from citrus pulp was prepared with diluted acid extraction and ethanol precipitation. Its rheological behavior was assessed under different thermal treatments at different concentrations. Three polysac-charides, named P-0, P-1 and P-2, were isolated by anion-exchange chromatography on a diethyl-aminoethyl ( DEAE) cellulose-52 column at 0, 0. 1, 0. 3 mol/L NaCl eluent, respectively. Their structural features were elucidated by determination of their molecular weight, sugar analyses, esterification degree analyses, Fourier transform infrared(FTIR) and 1H nuclear magnetic resonance(1H NMR) spectra. The results indicated that citrus pulp pectin was the typical shearing thinning non-newtonian fluid. The molecular weights of P-0, P-1 and P-2 were 752410, 286320, 131380, respectively. They belonged to the kind of acid polycose, which was abundant in uronic acid and low-esterified pectin with partial acetylesterification. P-0, P-1 and P-2 were main-ly made up of rhammogalacturonan-Ⅰ( RG-Ⅰ) structure and their monosaccharides compositions were mostly glucuronate, galactose, arabinose, rhamnose and fucose at different ratio. FTIR and NMR spectra implied that P-0, P-1 and P-2 owned pyranose rings and exhibited both α-and β-glycosidic bonds.