Aged citrus peel (Chenpi) is traditionally consumed with tea in Asian for synergistic flavor and health benefits. However, the structural evolution of citrus peel polysaccharides (Chenpi polysaccharides, CP) during aging and their regulatory role in the bioavailability of tea polyphenols remain poorly understood. In this study, CP from Chenpi aged 1–15 years were investigated for their impact on the digestive stability, epithelial transport, and delivery efficiency of epigallocatechin gallate (EGCG). Progressive depolymerization of CP altered their binding affinity toward EGCG (CP1 > CP15 > CP10 > CP5). Stronger binding led to greater digestive retention; CP1 showed the highest affinity (K_a = 3.02 × 10³ M^-1), enhancing EGCG retentionto 92.4 μg/mL (+376% vs. control), along with improved antioxidant capacity. However, its tight complexation hindered transmembrane transport. In contrast, CP15 formed compact nanospherical structures that enabled sustained EGCG release via weak multivalent interactions. Western blotting, TEM, and immunofluorescence revealed that CP15 downregulated efflux transporters (P-gp, MRP2) and reversibly remodeled tight junction protein ZO-1, promoting paracellular transport (P_app = 97.5 × 10^-7 cm·s^-1, 22.7-fold increase). These findings suggest a functional transformation of CP during aging—from stabilizing agents to barrier-modulating carriers—offering novel insights into structure-function relationships and a promising strategy for natural polysaccharide-based polyphenol delivery systems.

Citrus fruit contains a variety of bioactive ingredients and is particularly rich in dietary fiber (DF) with values of 50.13–68.00 g/100 g dry base. Citrus dietary fiber has excellent physicochemical properties in terms of water-holding capacity, water-swelling capacity and oil-holding capacity, making it widely used in meat products, baked products and dairy products. In addition, citrus dietary fiber has been proven to play a positive role in preventing several diseases such as diabetes, obesity, cardiovascular diseases and intestinal diseases due to diverse functional properties. In this review, the molecular composition, chemical structure, physicochemical properties, physiological activities and food application of citrus dietary fiber are summarized in order to provide a theoretical basis for the development and comprehensive utilization of citrus dietary fiber.

Some citrus plants are important medicinal and edible plants. Fructus Aurantii, Fructus Aurantii Immaturus, finger citron, Zhique (the dried fruit of Citrus grandis × junos), Citri Grandis Exocarpium (the dried unripe or almost ripe exocarp of C. grandis ‘Tomentosa’ or C. grandis (L.) Osbeck and Guangchenpi (the dried pericarp of C. reticulata ‘Chachi’) are common medicinal and edible citrus plant products, rich in flavonoids, coumarins, alkaloids, limonoids and volatile oils and having a variety of biological activities, such as antioxidant, anti-inflammatory, hypolipidemic, anti-depressant, antitussive and expectorant activities. They are widely used in the fields of health products, food and medicine. However, they have different bioactive components and clinical efficacies. Nowadays, their bioactive components and clinical efficacies have not been systematically summarized and compared. The bioactive components and bioactivities of these citrus products are systematically compared in this article, in order to provide a theoretical basis for further research and rational utilization of medicinal citrus plant resources.

In order to compare the conversion efficiencies of hesperidin into hesperitin-7-O-glucoside by single- and mixed-strain at 30 ℃ and 160 r/min, hesperidin was transformed by submerged fermentation using single and mixed (1:1) cultures of Fusarium nivale and Aspergillus sojae, and the fermentation products and the α-L-rhamnosidase activity of the fermentation broth the at different time points during fermentation were determined by high performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) and the pH of the fermentation broth was measured as well. The results showed that there was a significant difference between the mixed- and single-strain fermentations in the transformation of hesperidin to hesperitin-7-O-glucoside (P < 0.05). The mixed-strain fermentation gave a higher α-L-rhamnosidase activity (104.81 U/mL) than the single-strain fermentations (24.73 and 26.17 U/mL), and the fermentation of both strains was completed under acidic condition (pH 4-6). Mixed-strain fermentation could provide another way for the comprehensive development of orange peel, which could make full use of citrus by-products and at the same time avoid environmental pollution.

In this study, a ternary complex of zein with lecithin and propylene glycol alginate (PGA) was prepared by an anti-solvent method and applied to encapsulate β-carotene. The structural properties of β-carotene nanoparticles were studied. Moreover, the influences of environmental conditions such as temperature, pH and light on the stability of β-carotene nanoparticles were investigated. The results showed that compared with zein nanoparticles and zein-lecithin complexes, the ternary complex nanoparticles had a higher encapsulation efficiency for β-carotene (93.63%) and showed good stability against temperature and pH. In addition, the ternary complex was extremely effective in inhibiting β-carotene color degradation caused by exposure to ultraviolet light, keeping the average particle size below 250 nm. Therefore, zein-lecithin-propylene glycol alginate nanoparticles are expected to become an effective carrier for hydrophobic compounds.

The consumption of plant secondary metabolites-rich foods shows a positive effect on the regulation of human health. However, due to their poor solubility and chemical instability, the bioavailability of those secondary metabolites is usually low. The destruction of food composition caused by food processing is an important condition for the release of plant secondary metabolites, while food composition affects the absorption of plant secondary metabolites. In this review, we summarize the effects of different food components such as lipids and proteins as well as food processing methods such as thermal processing, mechanical processing and fermentation on the bioavailability of plant secondary metabolites. We expect that this review will provide a theoretical basis for improving the bioavailability of plant secondary metabolites in the daily diet.

Lutein, a dietary carotenoid, has various pharmaceutical functions such as protecting retinal pigment epithelial cells from damage caused by blue light, preventing cardiovascular and cerebrovascular diseases and anti-tumor activity. It is also a natural food colorant and antioxidant. The application of lutein in foods is hindered by its poor water solubility, chemical instability, and low oral bioavailability. To solve this problem, delivery systems have been developed. This review discusses the factors limiting lutein application, and summarizes the current status of research on food delivery systems for lutein encapsulation. We anticipate that this review will provide a reference for further research and application of lutein.

In order to explore the effect of different dietary structures (normal diet, high-protein diet, high-fat diet, high-sugar diet) on the bioavailability and antioxidant activity of citrus carotenoids, the changes in the carotenoid content, ferric reducing capacity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity of mandarin pulp were monitored during in vitro simulated digestion. The correlation between carotenoid content and antioxidant activity was also evaluated. The results showed that as digestion progressed, the contents of total carotenoids and two carotenoid monomers in mandarin pulp mixed with whey protein, soybean oil and corn starch in four different proportions decreased continuously and the antioxidant activity of carotenoids in the four groups also decreased significantly (P < 0.05). Among these groups, the content of carotenoids in the high-fat diet group was higher at all digestion stages, and the antioxidant activity of carotenoids in this group was also stronger. There was a significantly positive correlation between the antioxidant activity and content of citrus carotenoids (P < 0.05). The comprehensive analysis showed that dietary structures had a great impact on the bioavailability and antioxidant activity of citrus carotenoids. The bioavailability of carotenoids in the high-fat diet group was (24.08 ± 1.78)% and significantly higher than that ((19.26 ± 1.06)%) in the normal diet group (P < 0.05), and the antioxidant activity of carotenoids in the high-fat diet group was the strongest. The bioavailability of carotenoids in the high-protein diet group was (15.27 ± 0.90)% and significantly lower than that in the normal diet group (P < 0.05), while there was no significant difference in carotenoid bioavailability between the high-sugar ((19.71 ± 1.58)%) and normal diet groups. This study suggests that high-fat diet can significantly improve the bioavailability and antioxidant activity of citrus carotenoids.

In this study, low-sugar citrus jam was prepared from either ‘Jiuyuehong’ navel orange or Yichang tangerine by two different methods: high hydrostatic pressure at 500 MPa for 10 min, and heat treatment (water bath heating 100 ℃ for 30 min). The effects of high hydrostatic pressure and heat treatment on the quality and rheological properties of low-sugar citrus jam were investigated by analyzing physicochemical, sensory, color, rheological and texture properties. The results showed that high hydrostatic pressure and heat treatment reduced the content of total phenols in navel orange jam by 13.67% and 7.34% and in tangerine jam by 41.41% and 15.32%, respectively. Compared with the untreated citrus jam, heat treatment caused significant browning in both citrus jams, with total color difference (∆E) greater than 2. High hydrostatic pressure treatment significantly increased the brightness (L*) of the two citrus jams (P < 0.05). All four citrus jam samples were shear-thinning pseudoplastic fluids, and their storage (G’) and loss (G”) moduli increased with an increase in oscillation frequency; G’ was always greater than the corresponding G”, which is characteristic of an elasticity-dominant viscoelastic body. As far as navel orange jam was concerned, in the frequency range of 0.1–100 rad/s, G’ was largest in the heat treatment group (757.2–4390.5 Pa), medium in the high hydrostatic pressure group (375.5–2641.5 Pa), and smallest in the untreated group (177.25–973.95 Pa). A similar trend was observed for tangerine jam. In addition, compared to those prepared by heat treatment, high hydrostatic pressure treated citrus jams had lower firmness, stickiness and chewiness, and a more delicate mouthfeel. In conclusion, the quality of citrus jam prepared by high hydrostatic pressure is better. The results of this study can provide a reference for the development of new jams.

The contents, structures, physicochemical properties and functional characteristics of soluble dietary fiber (SDF), insoluble dietary fiber (IDF) and total dietary fiber (TDF) from the peel and pomace of Nanfeng tangerine, Zigui navel orange and Shatian pomelo were compared and analyzed. The results showed that TDF contents in citrus peel and pomace ranged from 19.96 to 44.26 g/100 g, and IDF/SDF ratios in tangerine peel, tangerine pomace and pomelo pomace were the closest to the recommended dietary ratio (2:1). All dietary fiber samples had obvious characteristic structures of polysaccharides, but their monosaccharide compositions and microstructures were different. Citrus pomace dietary fiber exhibited superior physicochemical properties and functional characteristics to peel dietary fiber, with pomelo pomace dietary fiber showing the best overall performance. Notably, pomelo pomace SDF had a water-holding capacity (WHC) of 28.46 g/g, a water swelling capacity (WSC) of 29.07 mL/g, an oil-holding capacity (OHC) of 3.38 g/g, a cholesterol adsorption capacity (CAC) of 22.56 mg/g, a nitrite ion adsorption capacity (NIAC) of 911.59 µg/g, a glucose adsorption capacity (GAC) of 2.64 mmol/g, and a glucose dialysis retardation index (GDRI) of 28.78% (15 minutes). In conclusion, citrus peel and pomace are good sources of high-quality dietary fiber and can be used as functional food components. This study can provide a theoretical basis for further refining the application of citrus dietary fiber and improving the added value of citrus by-products.