Abstract

In this study, Box–Behnken design was applied to optimize the ultrasound-assisted extraction (UAE) and heating extraction (HE) conditions for pectin production from pistachio green hull (PGH). The pectin extraction yield at optimal condition for UAE (ultrasound power of 150 W, pH of 1.5 and time of 24 min) and HE (temperature of 70 °C, time of 90 min and liquid to solid ratio of 40 v/w) methods was about 12.0 and 10.3%, respectively. In these conditions, the galacturonic acid content of UAE-pectin and HE-pectin was about 59.33 and 75.11%, respectively. Both pectin samples showed good emulsifying activity, water holding capacity and oil holding capacity. In addition, total phenol content, antiradical and surface activities of HE-pectin were higher than UAE-pectin. The degree of esterification of pectin produced by the HE method was higher than the UAE method, which was confirmed by FT-IR and ¹H-NMR analysis. The results of XRD patterns showed an amorphous structure with several crystalline portions for PGH pectin. The rheological properties of pectin solutions illustrated that in high frequencies, both pectin samples had a similar behavior (elastic), while in low frequencies, HE-pectin showed a viscous behavior. In the final, it should be stated that the UAE method significantly increased pectin yield using a lower processing time and consumed solvent, however, HE-pectin presented a better quality in comparison to UAE.

Graphic abstract

中文翻译：

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开心果副产物果胶的超声和热萃取：理化，结构表征和功能测定

摘要

在这项研究中，采用Box–Behnken设计来优化从开心果壳（PGH）生产果胶的超声辅助提取（UAE）和加热提取（HE）条件。在UAE（超声功率为150 W，pH为1.5和24分钟的时间）和HE（温度为70°C，时间为90分钟，液固比为40 v / w）的最佳条件下提取果胶分别约为12.0％和10.3％。在这些条件下，阿联酋果胶和HE-果胶的半乳糖醛酸含量分别约为59.33％和75.11％。两个果胶样品均显示出良好的乳化活性，保水能力和保油能力。另外，HE-果胶的总酚含量，自由基和表面活性均高于UAE-果胶。¹ H-NMR分析。XRD图谱的结果表明，对于PGH果胶，具有几个结晶部分的无定形结构。果胶溶液的流变特性表明，在高频率下，两种果胶样品都具有相似的行为（弹性），而在低频率下，HE-果胶表现出粘性行为。最后，应该指出的是，阿联酋方法使用较短的处理时间和消耗的溶剂即可显着提高果胶的产量，但是，与阿联酋相比，HE-果胶的质量更高。

图形摘要