Optimization of extraction with salicylic acid, rheological behavior and antiproliferative activity of pectin from Citrus sinensis peels

The effect of ultrasonic power on the physicochemical properties and antioxidant activities of frosted figs pectin

Ultrasound has been widely used in industry due to its high energy and efficiency. This study optimized the ultrasonic-assisted extraction (UAE) process of frosted figs pectin (FFP) using response surface methodology (RSM), and further investigated the effect of ultrasonic power on the structural characteristics and antioxidant activities of FFPs. The UAE method of FFP through RSM was optimized, and the optimal extraction process conditions, particle size of 100 mesh, pH value of 1.95, liquid-solid ratio of 47:1 (mL/g), extraction temperature of 50 °C and extraction time of 65 min, were obtained. The extraction rate of FFP under this condition was 37.97 ± 2.56 %. Then, the four FFPs modified by ultrasound were obtained by changing the ultrasonic power. Research had found that ultrasonic power had little effect on the monosaccharide composition, Zeta potential, as well as the thermal stability and appearance structure of the four FFPs. However, ultrasonic power had a significant impact on other properties of FFP: as the ultrasonic power increased, the DM% and particle size decreased continuously, while the total carbohydrate content increased. Meanwhile, ultrasonic power also had a significant impact on antioxidant activities of FFPs. From the research results, it could be seen that different ultrasonic power had certain changes in its spatial structure and properties, and the structural changes also affected the biological activity of FFP. The study of the effects of ultrasonic power on the physicochemical properties and biological activity of FFP lays the foundation for the development and application of FFP in food additives and natural drug carriers.

Extraction of high methoxyl pectin from unripe waste Ponkan mandarine (Citrus reticulata Blanco cv. Ponkan) with an eco-friendly solvent

The aqueous batch extraction of pectin from unripe Ponkan mandarin was evaluated for potential application in the food industry. A small central composite design with 4 variables (temperature, volume to mass ratio, pH, and mean particle size) and 3 levels was applied for pectin extraction optimization. Also, the kinetic of the pectin yield extraction was investigated at temperatures 70-90 °C, stirring rate of 100-700 rpm, ultrasound pretreatment system, and modeling using four mathematical models. The pectin extraction process was evaluated by yield of pectin and esterification degree. FTIR, TGA, and DTA were performed to evaluate the quality of pectin obtained. The small central composite design demonstrated that temperature and volume to mass ratio were significant variables, and the highest yield of pectin extraction was 11.62 % obtained at temperature and volume to molar ratio of 81.9 °C and 33.9 v/w %, respectively. Besides, the esterification degree showed higher than 70 % for all extraction conditions, suggesting high methoxyl pectin. The kinetics showed the stirring rate and the ultrasound pretreatment did not cause any significant alteration, while high temperatures proved to be beneficial to the rate and the yield of the pectin extraction. The best fit was provided by Fick's law, suggesting the extraction process is limited by internal mass transfer. FTIR showed the functional groups expected for pectin, and TGA and DTA indicated that the pectin obtained is proper for most food products, as only above 200 °C the pectin should degrade.

Novel edible films fabricated with HG-type pectin extracted from different types of hybrid citrus peels: Effects of pectin composition on film properties

This study investigated the valorization of novel HG-type hybrid citrus pectins derived from three cultivars: Setoka (ST), Kanpei (KP), and Shiranui (SH), and their application as packaging materials. The physicochemical properties of these pectins and their corresponding films were evaluated and compared to commercial citrus pectin. Significant variations were observed in pectin yield (18.15-24.12 %) and other physicochemical characteristics, such as degree of esterification (DE), degree of methoxylation (DM), and monosaccharide composition, among the different cultivars. All hybrid citrus pectins were classified as high-methoxy pectin types (66.67-72.89 %) with typical structural configurations like commercial citrus pectin. However, hybrid citrus pectin films exhibited superior physical properties, including higher mechanical strength, flexibility, and lower water solubility than commercial citrus pectin film, while maintaining similar transparency and moisture content. Additionally, the films displayed smooth and uniform surface morphology, confirming their excellent film-forming properties. Correlation analysis revealed that DE positively influenced mechanical properties (r = 1.0). Furthermore, the monosaccharide composition of pectins showed strong relationships (r = 0.8-1.0) with the film's mechanical and barrier properties. These findings highlight the potential of hybrid citrus pectin as potential packaging material, and the knowledge of the structure-function relationship obtained in this study could be useful for the tailored modification of citrus pectin-based packages.

Fabrication of Pickering emulsions stabilized by citrus pectin modified with β-cyclodextrin and its application in 3D printing

Pickering emulsions stabilized by polysaccharide particles have received increasing attention because of their potential applications in three-dimensional (3D) printing. In this study, the citrus pectins (citrus tachibana, shaddock, lemon, orange) modified with β-cyclodextrin (β-CD) were used to stabilize Pickering emulsions reaching the requirements of 3D printing. In terms of pectin chemical structure, the steric hindrance provided by the RG I regions was more conducive to the stability of the complex particles. The modification of pectin by β-CD provided the complexes a better double wettability (91.14 ± 0.14°-109.43 ± 0.22°) and a more negative ζ-potential, which was more beneficial for complexes to anchor at oil-water interface. In addition, the rheological properties, texture properties and stability of the emulsions were more responsive to the ratios of pectin/β-CD (R_β/C). The results showed that the emulsions stabilized at a φ = 65 % and a R_β/C = 2:2 achieved the requirements (shear thinning behavior, self-supporting ability, and stability) of 3D printing. Furthermore, the application in 3D printing demonstrated that the emulsions under the optimal condition (φ = 65 % and R_β/C = 2:2) displayed excellent printing appearance, especially for the emulsions stabilized by β-CD/LP particles. This study provides a basis for the selection of polysaccharide-based particles to prepare 3D printing inks which may be utilized in food manufacturing.

Comparison of characterization and antioxidant activity of different citrus peel pectins

Pectins obtained from citrus peel of different cultivars and growth regions were compared based on physicochemical properties and antioxidant activity in vitro. The physicochemical features were elucidated using Fourier transform infrared (FT-IR), molecular weight distribution, monosaccharide composition, thermal behaviors and flow behaviors. Results showed that the different cultivars and growing areas have significant effects on the properties of citrus peel pectins (CPPs). Citrus peel pectins extracted by acetic acid were highly heterogeneous polysaccharides with broad molecular weight distributions and had high proportions of the RG-I domain. Among the 10 kinds of citrus peel pectins, Shatangju (CPP-6) and Xuecheng (CPP-7) own superior antioxidant biological activity and Dahongpao (CPP-3) and Buzhihuo (CPP-9) had excellent functional properties (thermal stability and viscosity). According to the correlation analysis, molecular weight, galacturonic acid content and degree of methyl-esterification were beneficial to increase the thermal stability and viscosity of citrus peel pectins, while the rhamnose content, rhamnogalacturonan I region and lower molecular weight can improve citrus peel pectins antioxidant activity. Our findings suggest that CPP-6 and CPP-7 may be useful as a potential natural antioxidant in pharmaceutical and cosmetic industries. Meanwhile, CPP-3 has great application potential in high temperature food and CPP-9 can be used as a thickener or stabilizer in the food industry.

Multifunctional hydrogels based on oxidized pectin and gelatin for wound healing improvement

Gelatin (G) cross-linked with oxidized pectin (OP) was studied as a potential scaffold material for tissue engineering. The effect of oxidation on the chemical properties of pectin was investigated by determining the carbonyl and carboxyl amounts. The OP treatment led to a significant decrease of all values (Mn, Mw, [η] and Rh) determined by size exclusion chromatography (SEC) coupled on line with multiangle light scattering and viscometer detectors. Cross-linking parameters were elucidated by FTIR and TNBS assay. In general, the degree of crosslinking increased with the oxidation of pectin. It was found that the presence of the crosslinking agents caused a reduction in swelling and in the gelatin release which was determined by the BCA kit assay. From the hemolysis test, the membrane of red blood cells was not disrupted by the contact of films and the rate of release of hemoglobin was lower than 5%. The coagulation properties were evaluated by the dynamic blood clotting test. The G/OP hydrogels manifested a good activity of wound healing in the albino rats' model. Moreover, the films did not produce any unwilling symptoms. So, it was concluded that studied films have the potentiality to be used as wound healing biomaterials.

Interaction mechanism between soybean protein isolate and citrus pectin

In this study, citrus pectin (CP) and soybean protein isolate (SPI) were used as raw materials to prepare a complex. The interaction mechanism and structural changes between SPI and CP were deeply studied by fluorescence spectroscopy and Fourier infrared spectroscopy. The results show that CP has a strong quenching effect on SPI's endogenous fluorescence, and with the addition of CP, the endogenous fluorescence intensity of SPI decreased from 13,565.2 to 6067.3. The CP quenching of SPI is static quenching, and the number of combined bits is 1.26. The results of three-dimensional fluorescence spectra showed that the addition of CP reduced the polarity of SPI amino acid residue microenvironment and changed the protein structure. Hydrophobic interaction exists between CP and SPI. The results of three-dimensional fluorescence spectra showed that the addition of CP reduced the polarity of the amino acid residue microenvironment of SPI and changed the protein structure. Fourier transform infrared spectroscopy shows that CP could change the secondary structure of SPI by decreasing the α-helix and β-sheet, increasing β-rotation and irregular curl, destroying the ordered structure of SPI and increasing the polarity of the amino acids exposed to the solution. The microstructure analysis shows that SPI-CP composite system has honeycomb structure and dense pores. From the perspective of reaction thermodynamics, it was found that the addition of CP could improve the thermal stability of SPI and increase the denaturation temperature of SPI from 119.73 to 132.97°C. This study can provide a theoretical basis for the preparation of protein-pectin complexes and provides reference for their application in food grade gels and Pickering emulsions.