Degradation kinetics and structural characteristics of pectin under simultaneous sonochemical-enzymatic functions

The Influence of Citrus Pectin and Polyacrylamide Modified with Plant-Derived Additives on the Properties of α-TCP-Based Bone Cements

Materials based on highly reactive α-tricalcium phosphate (α-TCP) powder were developed and evaluated. Furthermore, the impact of different polymeric additives, such as citrus pectin or polyacrylamide (PAAM) modified with sago starch, neem flower, or rambutan peel, on the physiochemical and biological properties of the developed materials was assessed. The addition of modified PAAM shortened the setting process of bone cements and decreased their compressive strength. On the other hand, the addition of citrus pectin significantly enhanced the mechanical strength of the material from 4.46 to 7.15 MPa. The improved mechanical properties of the bone cement containing citrus pectin were attributed to the better homogenization of cementitious pastes and pectin cross-linking by Ca2+ ions. In vitro tests performed on L929 cells showed that 10% extracts from α-TCP cements modified with pectin are more cytocompatible than control cements without any additives. Cements containing PAAM with plant-derived modifiers show some degree of cytotoxicity for the highly concentrated 10% extracts, but for diluted extracts, cytotoxicity was reduced, as shown by a resazurin reduction test and live/dead staining. All the developed bone substitutes exhibited in vitro bioactivity, making them promising candidates for further biological studies. This research underscores the advantageous properties of the obtained biomaterials and paves the way for subsequent more advanced in vitro and in vivo investigations.

Effect of ultrasonic modification on the binding ability of pectin to anthocyanin

BACKGROUND

Pectin was considered as a potential candidate to improve the thermal stability of anthocyanins, and the binding ability of pectin to anthocyanins was influenced by its structure. In this study, sunflower pectins, modified by ultrasound (40 kHz) for different periods of time, were prepared and used to bind with anthocyanins, extracted from purple sweet potato.

RESULTS

Characterization and thermal stability of pectin-anthocyanin complexes were investigated. The ultrasonic modification of pectin resulted in many changes in pectin chemical structure, including degradation of neutral sugar side chains, breakage of methoxyl groups, and increased molecular flexibility. Extension of ultrasonic modification time led to greater changes in pectin chemical structure. Analysis of the binding ability, as determined by Fourier transform infrared spectroscopy and molecular dynamics simulations, revealed that the interaction between pectin and anthocyanins was driven by hydrogen bonding, electrostatic interaction, and hydrophobic interaction. Pectins with different ultrasonic modification times bound with anthocyanins to different extents, mainly resulting from an increase in the number of hydrogen bonds. According to high-performance liquid chromatographic analysis, during heating at 90 °C the stronger the binding ability of pectin and anthocyanin complex, the better was its thermal stability.

CONCLUSION

Ultrasonic modification of pectin could effectively enhance its binding ability to anthocyanin. © 2023 Society of Chemical Industry.

Effect of localized electrochemical pH and temperature synergistic modification on the structural and antibacterial properties of pectin/polyvinyl alcohol/zinc oxide nanorod films

Two low-methoxy pectins (LMPs) were obtained by local electrochemical pH modification using an H-type double-layer water bath sealed electrochemical cell at the voltage of 180 V for 3 h. The weight-average molecular weight (Mw) of citrus peel pectin (CPP) prepared in the anodic part at room temperature (CPP-A5/RT) and in the cathodic part at 5 °C (CPP-C5/RT) were 346 kDa and 328 kDa, respectively, and the degrees of methylation (DM) were 36.8 % and 11.9 %. Moreover, the second-order kinetic model was most appropriate for the degradation processes, as free radicals were generated in the anodic part and β-elimination occurred in the cathodic part. Subsequently, CPP-A5/RT and CPP-C5/RT were utilized to fabricate food packaging film blending with polyvinyl alcohol (PVA), bcZnO (ZnO coupled with bentonite and colophony) nanorods, and Ca2+ ions by casting method. Then the prepared films were studied for their ability to maintain the freshness of strawberries. The addition of Ca2+ ions and bcZnO nanorods increased the thickness, water contact angle (WCA), and mechanical properties of the composite films, while decreased water vapor permeability (WVP). Therefore, the CPP-based films, supplemented with bcZnO nanorods and crosslinked with Ca2+ ions by "egg-box" model, can serve as an antibacterial food packaging material for food preservation.

Modification methods, biological activities and applications of pectin: A review

Pectin is a complex and functionally rich natural plant polysaccharide that is widely used in food, medical, and cosmetic industries. It can be modified to improve its properties and expand its applications. Modification methods for natural pectin can be divided into physical, chemical, enzymatic, and compound methods. Different modification methods can result in modified pectins (MPs) exhibiting different physicochemical properties and biological activities. The objectives of this paper were to review the various pectin modification methods explored over the last decade, compare their differences, summarize the impact of different modification methods on the biological activity and physicochemical properties of pectin, and describe the applications of MPs in food and pharmaceutical fields. Finally, suggestions and perspectives for the development of MPs are discussed. This review offers a theoretical reference for the rational and efficient processing of pectin and the expansion of its applications.

Degradation, isomerization and stabilization of three dicaffeoylquinic acids under ultrasonic treatment at different pH

Dicaffeoylquinic acids (diCQAs) are found in a variety of edible and medicinal plants with various biological activities. An important issue is the low stability of diCQAs during extraction and food processing, resulting in the degradation and transformation. This work used 3,5-diCQA as a representative to study the influence of different parameters in ultrasonic treatment on the stability of diCQAs, including solvent, temperature, treatment time, ultrasonic power, duty cycle, and probe immersion depth. The generation of free radicals and its influence were investigated during the treatment. The stability of three diCQAs (3,5-diCQA, 4,5-diCQA and 3,4-diCQA) under the certain ultrasonic condition at different pH conditions was evaluated and found to decrease with the increase of pH, further weakened by ultrasonic treatment. Ultrasound was found to accelerate the degradation and isomerization of diCQAs. Different diCQAs showed different pattern of degradation and isomerization. The stability of diCQAs could be improved by adding epigallocatechin gallate and vitamin C.

The Preparation and Potential Bioactivities of Modified Pectins: A Review

Pectins are complex polysaccharides that are widely found in plant cells and have a variety of bioactivities. However, the high molecular weights (M_w) and complex structures of natural pectins mean that they are difficult for organisms to absorb and utilize, limiting their beneficial effects. The modification of pectins is considered to be an effective method for improving the structural characteristics and promoting the bioactivities of pectins, and even adding new bioactivities to natural pectins. This article reviews the modification methods, including chemical, physical, and enzymatic methods, for natural pectins from the perspective of their basic information, influencing factors, and product identification. Furthermore, the changes caused by modifications to the bioactivities of pectins are elucidated, including their anti-coagulant, anti-oxidant, anti-tumor, immunomodulatory, anti-inflammatory, hypoglycemic, and anti-bacterial activities and the ability to regulate the intestinal environment. Finally, suggestions and perspectives regarding the development of pectin modification are provided.

Grape-derived pectic polysaccharides alter the tannin and pigment composition of Cabernet Sauvignon red wines

Tannins, anthocyanins, and polymeric pigments are essential phenolic constituents of red wine because they provide color, color stability, and mouthfeel properties like astringency. The behavior of these compounds is significantly affected by pectic polysaccharides, whereby the extent of their influence on red wine quality depends on their structural features and their interactions with the polyphenols. In the present study, the composition of the pectic polysaccharides of commercially available Cabernet Sauvignon wines and their impact on anthocyanin, tannin, and polymeric pigment analyses was characterized. This was accomplished by preparation of polysaccharide deprived wines and comparison of the polyphenolic composition of both, the wines and their corresponding polysaccharide-free counterparts. The results show that the cell wall fragments enhance the spectral absorbance of anthocyanins by facilitating anthocyanin self-association, leading to a co-pigmentation-like effect. Low molecular weight pectins like rhamnogalacturonan II and polygalacturonic acids with a low degree of esterification are assumed to form soluble complexes with anthocyanins and also prevent protein precipitation of tannins, which was reduced by 6-13%. High molecular weight pectins with a high degree of esterification lead to the increased precipitability of pigments and tannins by a factor of 1.3 to 32.4 and 1.1 to 1.9, respectively, seemingly impairing the incorporation of anthocyanins in tannins to form precipitable polymeric pigments that are responsible for the longevity of red wine color. The increased precipitability of the pigments due to the interactions with the polysaccharides may indicate the formation of pigmented yet non-covalent aggregates that show comparable properties to the covalently formed precipitable pigments. The formation of those non-covalent structures may affect red wine color stability and astringency.

Valorization of citrus peel waste for the sustainable production of value-added products

Globally the generation and mismanagement of waste from fruit processing and post-harvest impose a severe burden on waste management strategies along with environmental pollution, health hazards. Citrus waste is one of such worrying fruit waste, which is rich in several value-added chemicals, including pectin. Pectin is a prebiotic polysaccharide possessing a multitude of health benefits. Citrus pectin has excellent gelling, thickening, water holding capacity, and encapsulating properties, which pave its functionality in versatile industrial fields including food processing and preservation, drug and therapeutic agents, cosmetics, and personal care products. The utilization of citrus wastes to derive valuable bioproducts can offer an effective approach towards sustainable waste management. With the ever-increasing demand, several strategies have been devised to increase the efficiency of pectin recovery from citrus waste. This review article discusses the sources, effect, and technology-mediated valorization of citrus waste, the functional and nutritive application of pectin along with its socio-economic and environmental perspective.

Ultrasound-assisted enzymatic hydrolysis of yeast β-glucan catalyzed by β-glucanase: Chemical and microstructural analysis

The purpose of this study was to investigate the effect of ultrasound-assisted enzymolysis on modified solubilization of yeast β-glucan and its related mechanism. The depolymerization effects of this system on the physicochemical properties and structural features of the degraded fragments were studied systematically. The structure and physicochemical properties of the samples showed that the solubility of yeast β-glucan achieved 75.35 % after modification; and ultrasonic enzymatic enhanced the degradation efficiency. The yeast β-glucan obtained after solubilization and modification owned better antioxidant activities. The yeast β-glucan particles become obviously smaller, sparsely dispersed in the aqueous solution and the stability was improved. In addition, the hydrogen bonds in yeast β-glucan native triple helix structure were partially broken. Moreover, the disruption of yeast β-glucan's original structure made it decreased thermostability and easier to dissolve in water. The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of yeast β-glucan and the small-strand degradation fragments. Therefore, this research can provide a feasible and effective approach for improving solubility of water-insoluble yeast β-glucan to enlarge its food and biomedical applications.

Structural Determination of Pectins by Spectroscopy Methods

Plant polysaccharides include pectins, which are responsible for an important role in plant physiology and are part of the plant cell wall. These compounds are known as gelling and stabilizing agents, which are widely used in the food industry. The scientific literature lacks precise information on the spectroscopy of apple pectin and citrus pectin. Therefore, the aim of this work was to test and compare the physicochemical properties of these compounds. The curves of FT-IR, NMR, ESI-MS, and thermogravimetric analysis (TGA) of pectin samples were measured and discussed. The analysis of the spectroscopic results confirms that the isolated pectins using various enzymes (xylanase and cellulase) have a structure similar to the commercially available pectin (PectaSol-C), with a noticeable change in morphology. These characteristics are helpful for further basic research and application.

Conjugation of soy protein isolate (SPI) with pectin: effects of structural modification of the grafting polysaccharide

Recently, there has been a great interest in enhancing the emulsifying properties of soy protein isolate (SPI) by Maillard reaction. As a commonly-used grafting polysaccharide, pectin has proved useful in modifying proteins. However, effects of its structural characteristics on conjugation are still not fully understood. To address this problem, we employed alkaline or/and enzymatic treatments to modify pectin and obtained three modified samples. Structural characteristics of pectin, including the molecular weight, degree of methoxylation and acetylation, and monosaccharide compositions were measured. When conjugated with SPI, pectin with lower molecular weight and less main chains induced higher conjugate yield. Fluorescence intensity and surface hydrophobicity of all conjugates markedly reduced compared to the original SPI, suggesting a more loosened protein structure after Maillard reaction. In this study, the enzymolysis pectin proved an optimum grafting polysaccharide considering the simple preparation procedures and the highest emulsifying properties of its resulting conjugates.

Trends in "green" and novel methods of pectin modification - A review

Modification of hydrocolloids to alter their functional properties using chemical methods is well documented in the literature. There has been a recent trend of adopting eco-friendly and "green" methods for modification. Pectin, being a very important hydrocolloid finds its use in various food applications due to its gelling, emulsifying, and stabilizing properties. The adoption of various "green" methods can alter the properties of pectin and make it more suitable for incorporation in food products. The novel approaches such as microwave and pulsed electric field can also be utilized for solvent-free modification, making it desirable from the perspective of sustainability, as it reduces the consumption of organic chemicals. Pectic oligosaccharides (POSs) produced via novel approaches are being explored for their biological properties and incorporation in various functional foods. The review can help to set the perspective of potential scale-up and adoption by the food industry for modification of pectin.

Effect of Extraction Procedures with Ultrasound and Cellulolytic Enzymes on the Structural and Functional Properties of Citrus grandis Osbeck Seed Mucilage

The structural and functional properties of Citrus grandis Osbeck (CGO) seed mucilage by different extraction practices, including conventional citrate buffer, ultrasonic-assisted (UAE), enzymatic-assisted extraction (EAE) with cellulase or Celluclast^® 1.5 L and various ultrasonic-assisted enzymatic extraction (UAEE) procedures were investigated. It was found that CGO seed from agricultural and processing byproducts is an excellent new source of high methoxyl pectin with quite high intrinsic viscosity (about 108.64 dL/g) and molecular weight (about 1.9 × 10⁶) as compared with other pectin sources. UAEE with Celluclast^® 1.5 L enhanced the extraction yield most pronouncedly (about 2.3 times). Moreover, the monosaccharide composition of CGO seed mucilage is least affected by EAE with Celluclast^® 1.5 L. In contrast, EAE with cellulase dramatically reduces the galacturonic acid (GalA) content to less than 60 molar%, and increases the glucose (Glc) content pronouncedly (to about 40 molar%), which may be considered as an adverse effect in terms of pectin purity. Though extraction procedures involved with ultrasound and cellulolytic enzymes generally show a decrease in GalA contents, weight average molar mass and intrinsic viscosity, EAE with Celluclast^® 1.5 L is least affected, followed by UAE and UAEE with Celluclast^® 1.5 L. These features can be leveraged in favor of diversified applications.

Changes in pectin characteristics of jujube fruits cv "Dongzao" and "Jinsixiaozao" during cold storage

Softening is one of the main factors affecting market value and consumer preferences for jujubes, and it was closely related to the modification and depolymerization of pectin. Changes in characteristics of three pectins (water-soluble pectin (WSP), sodium carbonate-soluble pectin (SSP) and chelate-soluble pectin (CSP)), including their contents, degree of methylesterification (DM), neutral sugar compositions, the molecular weight (M_w ) distributions and nanostructures, from two jujube fruits cv Dongzao (DZ) and Jinsixiaozao (JS) during cold storage were assessed. The results showed that variation in pectin characteristics during cold storage was similar between DZ and JS. The reduction of firmness corresponded to a conversion of water-insoluble pectin to WSP during cold storage. DM of WSP presented an increase trend in the late storage. Rhamnose (Rha), arabinose (Ara) and glucose (Glc) were the crucial compositions in three pectins, and most neutral sugar compositions in three pectins first increased and then decreased during cold storage. Changes in the ratio of (galactose (Gal)+Ara)/Rha and Ara/Gal represented that the branch chains of rhamnogalacturonan-I in three pectins depolymerized after storage. The high M_w in WSP and SSP of jujubes were solubilized and extensively depolymerized into pectin with lower M_w after storage. AFM images showed an increase in short chains and branch structures of three pectins after storage. Overall, three pectins in DZ and JS depolymerized and solubilized during cold storage. WSP and SSP were more contributed to the softening of jujubes compared to CSP, and they played the critical role for regulating the softening of jujube fruits during cold storage. PRACTICAL APPLICATION: Softening is one of the main factors affecting market value and consumer preferences for jujubes, and it was closely related to the modification and depolymerization of pectin. Changes in characteristics of three pectins (WSP, SSP, CSP), including their contents, degree of methylesterification, neutral sugar compositions, the molecular weight distributions and nanostructures, from two jujube fruits cv Dongzao (DZ) and Jinsixiaozao (JS) during cold storage were assessed. Three pectins in DZ and JS depolymerized and solubilized during cold storage. WSP and SSP were more contributed to the softening of jujubes compared to CSP, and they played the critical role for regulating the softening of jujube fruits during cold storage. This study would elucidate the mechanism of jujube softening and help to regulate the postharvest quality during cold storage.

Effects of High-Pressure Homogenization on Pectin Structure and Cloud Stability of Not-From-Concentrate Orange Juice

Not-from-concentrate (NFC) juice is popular with consumers due to its similarity to fresh fruit juice in taste, flavor, and beneficial nutrients. As a commonly used technology in fruit juice production, high-pressure homogenization (HPH) can enhance the commercial value of juice by improving the color, flavor, taste, and nutrient contents. In this study, the effects of HPH on the pectin structural properties and stability of NFC orange juice were investigated. The correlations between HPH-induced changes in the structure of pectin and the stability of orange juice were revealed. Compared with non-homogenized orange juice, HPH increased the galacturonic acid (GalA) content and the linearity of pectin, while decreasing the molecular weight (Mw), pectin branching, and rhamnogalacturonan (RG) contribution, and cracks and pores of different sizes formed on the surface of pectin, implying depolymerization. Meanwhile, with increasing pressure and number homogenization of passes, HPH effectively improved the stability of NFC orange juice. HPH can effectively prevent the stratification of orange juice, thereby promoting consumer acceptance and endowing a higher commercial value. The improvement of the stability of NFC orange juice by HPH was related to the structural properties of pectin. Turbidity was significantly (P < 0.01) positively correlated with GalA and pectin linearity, but was significantly (P < 0.01) negatively correlated with Mw, RG contribution, and pectin branching. Modification of pectin structure can improve the stability of NFC orange juice. In this work, the relationship between the pectin structure and stability of NFC orange juice is elucidated, providing a path toward improving consumer acceptance and enhancing the palatability and nutritional and functional qualities of orange juice. Manufacturers can use this relationship to modify pectin directionally and produce high-quality NFC orange juice beverages.

Effects of ultrasound on the enzymatic degradation of pectin

Ultrasound-assisted enzymatic maceration (UAEM) has gained considerable interest in the fruit juice industry, owing to its potential to increase juice yield and content of polyphenols while simultaneously saving time and energy. In this study, the effects of UAEM (ultrasonic probe, 20 kHz, 21 W*cm^-2 and 33 W*cm^-2) on pectin degradation in a continuous circulation system were investigated over 60 and 90 min. Main pectinolytic enzymes activities of (polygalacturonase, pectin lyase and pectin methylesterase) of a commercial enzyme preparation were examined for individual synergistic effects with US. Pectin hydrolysis by UAEM differed significantly compared to treatment with ultrasound or enzymes alone regarding the profile of degradation products compared to treatment with ultrasound or enzymes alone. Ultrasound fragmented pectin to less branched oligomers of medium molecular weight (Mp approx. 150 kDa), which were further degraded by pectinolytic activities. The low molecular weight fraction (<30 kDa), which is known to be beneficial for juice-quality by adding nutritional value and stabilizing polyphenols, was enriched in small oligomers of homogalacturonan-derived, rhamnogalacturonan I-derived, and rhamnogalacturonan II-derived residues. Synergistic effects of ultrasound application enhanced the effective activities of polygalacturonase and pectin lyase and even prolonged their performance over 90 min, whereas the effective activity of pectin methylesterase was not affected. Final marker concentrations determined by each enzyme assay revealed a considerable higher total process output after UAEM treatment at reduced temperature (30 °C) comparable to the output after conventional batch maceration at 50 °C. The obtained results demonstrate the high potential of UAEM to produce high-quality juice by controlling pectin degradation while reducing process temperature and equally highlight the matrix and enzyme specific effects of a simultaneous US treatment.

Effect of high hydrostatic pressure-assisted pectinase modification on the Pb2+ adsorption capacity of pectin isolated from sweet potato residue

Novel pectin derived from sweet potato residue was modified by high hydrostatic pressure (HHP)-assisted pectinase and then used for Pb²⁺ removal from aqueous solutions. The removal characteristics and mechanisms were also investigated. Results showed that modified sweet potato pectin exhibited greater adsorption performances for Pb²⁺ than that of natural ones, and showed excellent eco-friendly properties and good potential for adsorption of some other heavy metals (such as Cu²⁺). The adsorption curves were much more conformed to Langmuir model, and the highest capacity for Pb²⁺ adsorption was 263.15 mg/g with 1.00% pectin at pH 7. Chemical adsorption process of pectin for Pb²⁺ absorption involved O-containing functional groups (O-H, COO-), cation exchange, and along with electrostatic interactions. Overall, the results in this study indicated that sweet potato pectin modified with HHP-assisted pectinase had the potential to become an environmentally friendly coagulant-flocculant agent for the heavy metal adsorption, especially for Pb²⁺.

An Atomic Force Microscopy Study on the Effect of β-Galactosidase, α-L-Rhamnosidase and α-L-Arabinofuranosidase on the Structure of Pectin Extracted from Apple Fruit Using Sodium Carbonate

The enzyme driven changes in plant cell wall structure during fruit ripening result in debranching, depolymerization and solubilization of pectin polysaccharides, which has an effect in terms of the postharvest quality losses in fruit. Atomic force microscopy (AFM) has revealed that diluted alkali soluble pectins (DASP) from fruit and vegetables have an interesting tendency to self-assemble into regular structures. However, the mechanism is not yet fully understood. The current study is aimed at investigating the role of neutral sugars, namely galactose, rhamnose and arabinose in the formation of the branched structure of DASP. β-galactosidase, α-L-rhamnosidase and α-L-arabinofuranosidase enzymes were used for the treatment of DASP extracted from Golden Delicious apple flesh (Malus domestica cv. Golden Delicious). The effects of the selective degradation of pectic polysaccharides after 15, 30, 60, 90 and 120 min of incubation were observed using AFM. The α-L-rhamnosidase enzyme activity on pectin extracted with Na2CO3 did not cause any visible or measurable degradation of the molecular structure. The moderate effects of β-galactosidase enzymatic treatment suggested the possible role of galactose in the branching of DASP molecules deposited on mica. Data obtained for α-L-arabinofuranosidase indicated the crucial role of arabinose in the formation and preservation of the highly branched structure of the DASP fraction.

Manothermosonication (MTS) treatment by a continuous-flow system: Effects on the degradation kinetics and microstructural characteristics of citrus pectin

Modified pectin (MP) was reported to have increased bioactivities compared with the original one. However, traditional modification methods such as using an acidic solvent with heating are not only costly but causing severe pollution as well. In this study, manothermosonication (MTS) with a continuous-flow system was utilized to modify citrus pectin. The citrus pectin (5 g/L) treated by MTS (3.23 W/mL, 400 kPa, 45 °C) exhibited lower molecular weight (Mw, 248.17 kDa) and PDI (2.76). The pectin treated by MTS (400 KPa, 45 °C, 5 min) exhibited a narrower Mw distribution and lowered more Mw (48.8%) than the ultrasound(US)-treated (23.8%). Pectin degradation data fitted well to kinetic model of 1/Mw_t -1/Mw₀ = kt (45-65 °C). A lower activation energy of 13.33 kJ/mol was observed in the MTS treatment compared with the US-treated (16.38 kJ/mol). The MTS-treated pectin lowered the degree of methoxylation (DM), mol% of rhamnose and galacturonic acid (GalA) while increased mol% of galactose (Gal), xylose (Xyl), and arabinose (Ara). The ¹H and ¹³C nuclear magnetic resonance showed that MTS could not alter the primary structures of citrus pectin. However, an elevated (Gal + Ara)/Rha and reduced GalA/(Rha + Ara + Gal + Xyl) molar ratios after MTS suggested that MTS resulted in more significant degradation on the main chains and less on the side chains of pectin, in agreement with the result of atomic force microscope. Moreover, the MTS-treated pectin exhibited a higher 1,1-diphenyl-2picryl hydrazyl radical scavenging capacity compared with original pectin.

Treatment with Subcritical Water-Hydrolyzed Citrus Pectin Ameliorated Cyclophosphamide-Induced Immunosuppression and Modulated Gut Microbiota Composition in ICR Mice

Subcritical water can effectively hydrolyze pectin into smaller molecules while still maintaining its functional regions. Pectic heteropolysaccharide can mediate immune regulation; however, the possible effects of subcritical water-hydrolyzed citrus pectin (SCP) on the immune response remain unclear. Therefore, the effects of SCP on immunomodulatory functions and intestinal microbial dysbiosis were investigated using a cyclophosphamide-induced immunosuppressed mouse model. In this research, immunosuppressed ICR mice were administrated with SCP at dosages of 300/600/1200 mg/kg.bw by oral gavage, and body weight, immune organ indexes, cytokines, and gut microbiota were determined. The results showed that subcritical water treatment decreased the molecular mass and increased the content of galacturonic acid in citrus pectin hydrolysates. Meanwhile, the treatment with SCP improved immunoregulatory functional properties and bioactivities over the original citrus pectin. For example, SCP protected immune organs (accelerated recovery of immune organ indexes) and significantly enhanced the expression of immune-related cytokines (IL-2, IL-6, IFN-γ, and TNF-α). The results of the 16S rDNA sequencing analysis on an IlluminaMiSeq platform showed that SCP normalized Cy-induced gut dysbiosis. SCP ameliorated Cy-dependent changes in the relative abundance of several taxa, shifting the balance back to normal status (e.g., SCP increased beneficial Muribaculaceae, Ruminococcaceae, Bacteroidaceae, and Prevotellaceae while decreasing pathogenic Brevundimonas and Streptococcus). The results of this study suggest an innovative application of citrus pectin as an immunomodulator.

Characterization of partial acid hydrolysates of citrus pectin for their pasting, rheological and thermal properties

Pectin was subjected to acid hydrolysis with hydrochloric acid for 30 and 60 min to prepare partial hydrolysates (PH30 and PH 60). The influence of acid hydrolysis on the physico-chemical and functional properties were assessed for their potential applications in foods. Acid hydrolysis significantly reduced the molecular weight and viscosity of pectin in a time dependent manner. Steady shear properties revealed a shear-thinning behavior for NP and PH 30 while Newtonian behavior was observed for PH 60. Oscillatory measurements revealed a viscoelastic behavior for NP while a viscous liquid like behavior was observed for PH30. DSC measurements also revealed reduced thermal stability of pectin hydrolysates in comparison to native pectin. The results of the present study suggested that pectin hydrolysates with improved solubility can be used in various food products as a source of dietary fiber without modifying the texture and palatability of food products.

Manosonication extraction of RG-I pectic polysaccharides from citrus waste: Optimization and kinetics analysis

To better understanding the potential of manosonication to accelerate the extraction of RG-I pectic polysaccharides from citrus wastes, alkaline-mediated manosonication extraction (MSE) was optimized using a Box-Behnken design, and the extraction kinetics model was analyzed. The single-factor method revealed that NaOH significantly impacted on the yield and RG-I characterizations (Rha mol% and (Gal+Ara)/Rha ratio), whereas other factors were focused on influences of yields. In the developed quadratic polynomial model, the maximum extraction yield of 25.51 ± 0.81 % was obtained with sonication at 42 ℃, 40 % amplitude, and 250 kPa for 20 min. The kinetics study demonstrated that MSE facilitated the extractability, dissolution and degradation of pectin, resulting in the highest extractability of 27.83 % compared with ultrasonic extraction (22.86 %) and alkaline extraction at high (24.71 %) and low temperature (20.21 %). Rheology and thermal analyses verified the change in polymerization by MSE and the potential functional applications of the RG-I pectic polysaccharides.

Formation of soy protein isolate (SPI)-citrus pectin (CP) electrostatic complexes under a high-intensity ultrasonic field: Linking the enhanced emulsifying properties to physicochemical and structural properties

In this study, a high-intensity ultrasonic field was applied to the electrostatic interactions between soy protein isolate (SPI) and citrus pectin (CP). The emulsifying properties of SPI-CP soluble complexes formed under different ultrasound powers and durations were investigated and peaked at 630 W for 10 min. Micrographs of emulsions revealed that ultrasound-treated complexes generated a more homogeneous emulsion with significantly reduced and uniformly-distributed droplet sizes. To better understand the mechanism for the improved emulsifying properties, the physicochemical and structural properties of the SPI-CP complexes at pH 3.5 with and without ultrasound treatment were investigated. It was revealed that ultrasound increased the absolute values of the zeta potential and surface hydrophobicity of complexes, but significantly decreased their particle sizes, fluorescence intensity and turbidity. Results indicated that cavitation effects resulted in structural modifications in both biomacromolecules, as well as enhanced the electrostatic interactions between SPI and CP, which in combination contributed to the more desirable emulsifying properties of the complex.

Ultrasonic-assisted citrus pectin modification in the bicarbonate-activated hydrogen peroxide system: Chemical and microstructural analysis

The modified pectin (MP) showed the improved functional properties than the native one. The aim of present study was to develop the ultrasonic accelerated bicarbonate-hydrogen peroxide system for pectin modification to generate short fragments with advanced bioactive properties. The depolymerization effects of this system on the physicochemical properties, structural features, and bioactivity of the degraded fragments were studied systematically. The results indicated that the molecular weight of pectin was reduced drastically from 1088 kDa to 33 kDa within 50 min under an optimized condition (M_H2O2-M_NaHCO3 = 1:2.5, 50 °C, and ultrasound intensity = 11.4 W/cm³). The resulting fragments also showed lower degree of methoxylation and rheological viscosity. The investigation on the sample structures and active oxygen species demonstrated that the highly active O₂^- species generated from HCO₄^- of NaHCO₃-H₂O₂ acted preferentially on the GalA backbone in the HG region, while the RG-I region was maintained; and ultrasound enhanced the degradation efficiency via both chemical effects (increasing the transformation of free radicals) and mechanical effects (disaggregating polysaccharide clusters). The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of pectin and the small-strand degradation fragments. Moreover, ultrasound and NaHCO₃-H₂O₂ treatment induced high galactose content in the degraded products, contributing to an improved inhibitory activity against A549 lung cancer cells, as shown by MTT assay.

Comparison of citrus pectin and apple pectin in conjugation with soy protein isolate (SPI) under controlled dry-heating conditions

In this study, we selected two most commonly-available commercial pectin, i.e. citrus pectin and apple pectin as the grafting polysaccharides to prepare soy protein isolate-pectin conjugates. Despite the similar degrees of methoxylation and acetylation for two pectin samples, apple pectin showed much more complex structures compared to citrus pectin, with a 2.20-fold higher molecular weight and large numbers of side chains. The conjugates were prepared under controlled dry-heating conditions and achieved the degree of graft of 25.00% and 21.85% for citrus and apple pectin, respectively. Formation of the conjugates was further confirmed by SDS-PAGE gel electrophoresis and IR spectra. Attributed to the strong steric-hindrance effect of pectin, the fluorescence intensity and surface hydrophobicity of the soy protein isolate were significantly decreased after Maillard reaction. However, both solubility and emulsifying properties of the conjugates were significantly improved. Results indicated that both pectin samples played favorable roles in protein modification.

Interactions of Anthocyanins with Pectin and Pectin Fragments in Model Solutions

Anthocyanins determine the color and potential health-promoting properties of red fruit juices, but the juices contain remarkably less anthocyanins than the fruits, which is partly caused by the interactions of anthocyanins with the residues of cell wall polysaccharides like pectin. In this study, pectin was modified by ultrasound and enzyme treatments to residues of polysaccharides and oligosaccharides widely differing in their molecular weight. Modifications decreased viscosity and degrees of acetylation and methylation and released smooth and hairy region fragments. Native and modified pectin induced different effects on the concentrations of individual anthocyanins after short-term and long-term incubation caused by both hydrophobic and hydrophilic interactions. Results indicate that both pectin and anthocyanin structure influence these interactions. Linear polymers generated by ultrasound formed insoluble anthocyanin complexes, whereas oligosaccharides produced by enzymes formed soluble complexes with protective properties. The structure of the anthocyanin aglycone apparently influenced interactions more than the sugar moiety.

Preparation of low molecular weight heparin using an ultrasound-assisted Fenton-system

Heparin, a high-molecular weight acidic polysaccharide, has raised much interest in the field of biomedical research due to its multiple bio-functions. The anticoagulant application of heparin in routine clinical practice, however, has been limited as the large molecular size of heparin can reduce its subcutaneous bioavailability and lead to severe adverse consequences such as thrombocytopenia. Here, we report a highly efficient and convenient method to depolymerize high-molecular weight, unfractionated heparin (UFH), into low molecular weight heparin (LMWH) by combining physical ultrasonic treatment with the chemical Fenton reaction, referred to as sono-Fenton. We found that this combination treatment synergistically degraded UFH into a LMWH of 4.87 kDa within 20 min. We characterized the mechanism of sono-Fenton heparin degradation through multiple approaches, including HPLC-SAX, disaccharide composition, FT-IR, NMR and top-down analysis, and found that the uronic acid residue in heparin was the most susceptible site attacked by OH radicals produced in the sono-Fenton process. Importantly, the LMWH prepared by this method had significantly higher anticoagulant activity than UFH and other LMWHs. This approach represents an effective method to produce heparin with improved activity and should be potentially useful for heparin production in the pharmaceutical industry.

Degradation of carboxymethylcellulose using ultrasound and β-glucanase: Pathways, kinetics and hydrolysates' properties

In order to provide an efficient way to degrade carboxymethylcellulose (CMC), three pathways were investigated: enzymolysis, combination of ultrasound pretreatment and enzymolysis, and sonoenzymolysis. Effects of these treatments on enzymatic kinetics, degradation kinetics and properties of degraded CMC were investigated. The degradation degree of CMC was increased by 18.90% and 35.73% with ultrasound pretreatment (at an intensity of 24 W/mL for 30 min) and sonoenzymolysis (at an intensity of 9 W/mL for 50 min), compared with that obtained under the traditional enzymolysis. Analysis of kinetics demonstrated that ultrasound, both pretreatment and combined with β-glucanase, could accelerate CMC degradation. Measurements of rheological properties, molecular weight and structures of CMC hydrolysates revealed that ultrasound broke the glycosidic bond of CMC chains without changing its primary structure. The sonoenzymolysis process was the most efficient method to degrade CMC, with potential to provide a way to obtain CMC with lowest molecular weight or viscosity.

Ultrasound promotes enzymatic reactions by acting on different targets: Enzymes, substrates and enzymatic reaction systems

With the extensive application of enzyme-catalyzed reactions in numerous fields, improving enzymatic efficiency has attracted wide attention for reducing operating costs and increasing output. There are three targets throughout enzymatic reactions: the enzyme, substrate, and mixed reaction system. Ultrasound has been known to accelerate enzymatic reactions by acting on different targets. It can modify both enzyme and substrate macromolecules, which is helpful for enhancing enzyme activity and product yields. The synergistic effect of ultrasound and enzymes is widely reported to increase catalytic rates. The present review discusses the positive effect induced by ultrasound throughout the enzymatic process, including ultrasonic modification of enzymes, ultrasound assisted immobilization, ultrasonic pretreatment of substrates, and ultrasound assisted enzymatic reactions.

Effects of high hydrostatic pressure and high pressure homogenization processing on characteristics of potato peel waste pectin

To better understand the effects of high pressure processing on potato peel waste pectins, the structural characteristics, physicochemical properties, and morphological features of the pectin treated with high hydrostatic pressure (HHP) and high pressure homogenization (HPH) at 200 MPa for 5 min were studied. The potato peel waste pectins subjected to high pressure treatments exhibited increased galacturonic acid contents as well as decreased esterification degree, (Gal + Ara)/Rha ratio, and molecular weight. Furthermore, the potato peel waste pectins treated with high pressure had an increased viscosity and improved emulsifying properties. The morphological features, determined by atomic force microscopy, shown the degradation of side chains of the pectin induced by high pressure treatments. The results suggest that high pressure processing is an efficient technique to modify pectin from potato peel waste to a thickener or stabilizer agent, but high pressure homogenization shows a better effect.

Characteristics of pectinase treated with ultrasound both during and after the immobilization process

In this study, ultrasound was applied both during and after the immobilization process and characteristics of different immobilized pectinase samples were studied. When introduced during the immobilization process, ultrasound at an intensity of 9WmL^-1 for 20min increased the immobilization yield 92.28% more than the control. When introduced to the already immobilized pectinase, ultrasound at an intensity of 4.5WmL^-1 for 10min increased the pectinase activity by 30.05%. Results of scanning electron microscope demonstrated that ultrasound increased surface area and loosened structures of immobilized enzymes. Higher V_max and lower K_m were obtained after ultrasound treatment, indicating the increased catalytic efficiency and enhanced affinity of immobilized pectinase. Furthermore, the optimum temperature and pH for free and immobilized pectinase remained unchanged at 50°C and pH 4. Thermostability, reaction stability and reusability of two ultrasound-treated pectinase enzymes slightly decreased due to structural matrix changes.

Fast preparation of RG-I enriched ultra-low molecular weight pectin by an ultrasound accelerated Fenton process

Pectin, a natural polysaccharide found in the cell wall of most higher plant such as citrus, has drawn much attention due to its potential beneficial role in facilitating the treatment of many diseases like cancer, hyper cholesterol and diabetes. However, the broad application of pectin faces great limitations as the large molecular size of pectin severely prevents its bioavailability in vivo. In this study, we report an effective and highly convenient approach to degrade natural pectin into lower molecular pectin. By combining ultrasound with Fenton system (US-Fenton), we show that ultrasound synergistically enhances the efficiency of Fenton reaction to degrade pectin into 5.5 kDa within only 35 minutes. Importantly, RG-I domain, the most effective portion of natural pectin, was well preserved and highly enriched. In addition, the antioxidant activities of US-Fenton-treated pectin was significantly elevated. The mechanism of this novel observation was further investigated through the multiple structural analyses including HPLC, IR and NMR. Taken together, we present a novel and convenient approach to generate ultra-low molecular weight pectin with high efficiency and higher bioactivity. We expect our approach will have broader applications in improving the bioavailability and bioactivity of other polysaccharide-based natural compounds.