Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part I. The effects on pectin extraction and structural properties

Authors: Zhao, Wei; Xu, Yixiang; Dorado, Christina; Chau, Hoa - Rose; Hotchkiss, Arland; Cameron, Randall - Randy

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2023
Publication Date: 12/9/2023
Citation: Zhao, W., Xu, Y., Dorado, C., Chau, H.K., Hotchkiss, A.T., Cameron, R.G. 2023. Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part I. The effects on pectin extraction and structural properties. Food Hydrocolloids. 149/109516. https://doi.org/10.1016/j.foodhyd.2023.109516.
DOI: https://doi.org/10.1016/j.foodhyd.2023.109516

Interpretive Summary: Pectin is a complex polysaccharide widely used in the food and pharmaceutical industries due to its gelling, thickening, and stabilizing properties. Pectin obtained with commercial extraction method is usually high-methoxyl (HM) and demethylation of pectin is needed to enable the pectin to gel without the requirement of high sugar added. Enzymatic demethylation of pectin with plant pectin methyl-esterase (PME) generates high quality pectin with desirable structural features but the cost is extremely high. In this study we report a pretreatment of fresh orange peel with high-pressure processing (HPP) before pectin extraction with the commercial method. The HPP-pretreatment modified pectin structure and increased the yield of subsequent pectin extraction. The physicochemical and structural properties of the extracted pectins were analyzed and the results indicate that the HPP-modified pectins had structural features similar to the effects of enzymatic demethylation of pectin with plant PME, suggesting that modification of pectin in source plant material before pectin extraction by HPP may be an efficient and economical way to generate pectin with desirable structural features, as well as increased yield of pectin extraction.

Technical Abstract: The possibility of making use of endogenous plant pectin methyl-esterase (PME) to modify pectin in source material prior to pectin extraction is proposed and explored in this study. This is based on the reports about activation of endogenous PME in plant-based foods by high-pressure processing (HPP) treatment. Fresh orange (Hamlin) peel from a local commercial juice plant was pretreated with HPP at different combinations of pressures and durations, followed by pectin extraction with a commercial method. The effects of HPP pretreatments on pectin yield, physicochemical and structural properties of the extracted pectins were determined. HPP pretreatment increased the yield of subsequent pectin extraction by 41.10 %. Compared to the control (pectin extracted from un-treated peel), pectins extracted from HPP pretreated peel (Hp) had a lowered degree of methyl-esterification (DM), which was accompanied by an increase in degree of blockiness (DB) of non-esterified galacturonic acid (GalA). GalA percentage content and linearity of pectin were higher while percentage neutral sugar content and degree of branching (DBr) were lower in Hp. The reduction in weight average molecular weight of Hp was minor and it was positively correlated with a reduction in neutral sugars, indicating an effect of pectin debranching without degradation of the pectin main chain. The effects of HPP on pectin main chain, degree and distribution of methyl-esterification in this study were similar to the reported effects of orange PME on extracted pectin. The structural features of the modified pectins were validated by Fourier Transform Infrared Spectroscopy (FTIR) analysis and a newly developed lateral flow assay (Zhao et al., 2022). The study indicates that HPP modification of pectin structure in fresh orange peel before pectin extraction may be an efficient and economical way to generate pectin with desirable structural features, as well as increased yield of pectin extraction.