Citrus pectin research advances: Derived as a biomaterial in the construction and applications of micro/nano-delivery systems

Citrus fruits are rich in pectin, phenolics, essential oils, and other bioactive. Pectin, as the main substance in the by-product (e.g., peel and pomace), has potential anti-inflammatory and immunomodulatory effects. This may arise through structural function as well as pectinolytic and its metabolites. The structural characteristics of pectin, such as neutral sugar side chains, molecular weight, and degree of methyl-esterification, determine the functional properties. Therefore, green extraction and modification techniques can be performed on pectin to improve bioactivity and encapsulation ability. In addition, green extraction techniques can obtain a high extraction yield of pectin, with the advantages of short time, low solvent usage, and environmental friendliness. Due to its biodegradability and low toxicity, citrus pectin holds great promise as a biomaterial for micro/nano delivery applications. Pectin can interact with cations, polysaccharides, and proteins to construct delivery systems, which can encapsulate polyphenols, essential oils, and probiotics in bioactives delivery and biofilm applications. Therefore, this paper compares six green extraction and three modification techniques for pectin, and discusses the influencing conditions and major structural changes. Recent advances in citrus pectin regarding the micro/nano-delivery systems construction and application are systematically summarized, which can provide a reference for the potential utilization of citrus pectin in the future.