Yield, Esterification Degree and Molecular Weight Evaluation of Pectins Isolated from Orange and Grapefruit Peels under Different Conditions

Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification “DE” and on molecular weight “Mw”. Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x1005 to 2.47x1005 g/mol for grapefruit pectin and from 1.639 x1005 to 2.471 x1005 g/mol for orange pectin.

以橙（Citrus sinensis）与葡萄柚（Citrus paradise）的果皮作为果胶（pectin）的提取原料，在不同条件下开展果胶提取实验。果皮采用两种使用状态：新鲜果皮与残留果皮（即完成精油提取后的果皮）。果胶提取过程中分别使用有机酸（柠檬酸）与无机酸（硫酸）作为提取试剂。本研究旨在评估提取条件对果胶得率、酯化度（DE）以及分子量（Mw）的影响。实验结果表明，采用残留果皮时的果胶得率更高。此外，两种果皮均可制备得到酯化度大于50%的高甲氧基果胶。分子量采用Mark-Houwink-Sakurada方程计算，该方程可描述分子量与特性黏度之间的关系；特性黏度则通过四种方程完成测定：Huggins方程、Kramer方程、Schulz-Blaschke方程以及Martin方程。葡萄柚果胶的分子量范围为1.538×10^5 至2.47×10^5 g/mol，橙果胶的分子量范围为1.639×10^5 至2.471×10^5 g/mol。