Physicochemical and functional properties of pectin extracted from the edible portions of jackfruit at different stages of maturity.

BACKGROUND: The physicochemical and functional properties of pectin (JFP) extracted from edible portions (including pericarp and seed) of raw jackfruit (an underutilized tropical fruit) at four different maturity stages (referred to as stages I, II, III, and IV) were characterized in terms of extraction yields, chemical composition, molecular weight, and antioxidant properties to evaluate its potential use in foods. RESULT: The JFP yield increased from 9.7% to 21.5% with fruit maturity, accompanied by an increase in the galacturonic acid content (50.1%, 57.1%, 63.6%, and 65.2%) for stages I-IV respectively. The molecular weight increased from 147 kDa in stage I to 169 kDa in stage III, but decreased to 114 kDa in stage IV, probably due to cell-wall degradation during maturation. The JFP was of the high methoxyl type and the degree of esterification increased from 65% to 87% with fruit maturity. The functional properties of JFP were similar to or better than those reported for commercial apple pectin, thus highlighting its potential as a food additive. Although the phenolics and flavonoids content of JFP decreased with fruit maturity, their antioxidant capacity increased, which may be correlated with the increased content of galacturonic acid upon fruit development. Gels prepared from JFP showed viscoelastic behavior. Depending on the maturity stage in which they were obtained, different gelation behavior was seen. CONCLUSION: The study confirmed the potential of pectin extracted from edible parts of jackfruit as a promising source of high-quality gelling pectin with antioxidant properties, for food applications. © 2022 Society of Chemical Industry.

Advances and prospects in the food applications of pectin hydrogels.

Pectin hydrogel is a soft hydrocolloid with multifaceted utilities in the food sector. Substantial knowledge acquired on the gelation mechanisms and structure-function relationship of pectin has led to interesting functions of pectin hydrogel. Food applications of pectin hydrogels can be categorized under four headings: food ingredients/additives, food packaging, bioactive delivery and health management. The cross-linked and tangly three-dimensional structure of pectin gel renders it an ideal choice of wall material for the encapsulation of biomolecules and living cells; as a fat replacer and texturizer. Likewise, pectin hydrogel is an effective satiety inducer due to its ability to swell under the simulated gastric and intestinal conditions without losing its gel structure. Coating or composites of pectin hydrogel with proteins and other polysaccharides augment its functionality as an encapsulant, satiety-inducer and food packaging material. Low-methoxyl pectin gel is an appropriate food ink for 3D printing applications due to its viscoelastic properties, adaptable microstructure and texture properties. This review aims at explaining all the applications of pectin hydrogels, as mentioned above. A comprehensive discussion is presented on the approaches by which pectin hydrogel can be transformed as a resourceful material by controlling its dimensions, state, and rheology. The final sections of this article emphasize the recent research trends in this discipline, such as the development of smart hydrogels, injectable gels, aerogels, xerogels and oleogels from pectin.

Formation and characterization of noncovalent ternary complexes based on whey protein concentrate, high methoxyl pectin, and phenolic acid.

Protein-polysaccharide-polyphenol noncovalent ternary complexes possess unique physicochemical, structural, and functional properties. In the present study, ternary complexes based on whey protein concentrate (WPC; 2%, wt/vol) and high methoxyl pectin (HMP; 0.5%, wt/vol) complexes and 0.2 to 0.6% (wt/vol) chlorogenic acid (CA) or rosmarinic acid (RA) were formed and characterized at 3 pH values (4, 4.5, and 5). The pH conditions were decided according to phase diagram of WPC and HMP during acidification. Fluorescence quenching experiments indicated that WPC-HMP complexes bound RA stronger than CA and the binding constant increased with increasing pH for both phenolic acids. Particle size of ternary complexes decreased and absolute ζ-potential increased with pH values changing from 4 to 5, and RA influenced the particle size of WPC-HMP complexes greater than CA. The CA and RA in ternary complexes showed good stability against UV light with pH order of pH 5 > pH 4.5 > pH 4. Fourier-transform infrared spectroscopy spectra indicated the involvement of hydrogen bonding between WPC-HMP and CA or RA. Antibacterial tests showed that ternary complexes had good antibacterial activity against Staphylococcus aureus and Escherichia coli at concentrations of 6.2 mg/mL and the ability increased with decreasing pH values. All ternary complexes possessed strong scavenging radical capacities with median inhibitory concentration (IC50) values ranging from 2.71 ± 0.05 to 6.20 ± 0.41 µg/mL. Antioxidative ability of ternary complexes increased as pH went up and WPC-HMP-RA showed significantly higher antioxidative property compared with WPC-HMP-CA. Data may provide useful information for rational design of ternary complexes and applications of the formed complexes in food matrices such as beverages and emulsions.

Optimization of calcium pectinate gel production from high methoxyl pectin.

BACKGROUND: Calcium pectinate (CaP) gel is traditionally prepared by de-esterifying high methoxyl pectin (HMP) to low methoxyl pectin (LMP), followed by gelation with calcium. To save both time and cost in the production of CaP gel, an alternative method was developed by the addition of CaCl2 to HMP at alkaline pH. To optimize the production, response surface methodology (RSM) was used to investigate the effects of temperature (30-50 °C), time (20-40 min) and pH (8-10) on yield, calcium content of the CaP gel and the degree of esterification (DE) of pectin following decalcification of CaP (DC-pectin). RESULTS: The linear term for pH had a significant effect (P < 0.01) on all three responses, whereas interaction effects were not significant (P > 0.01), except on the calcium content (P < 0.01). The optimized process conditions (temperature, time and pH) to obtain maximum CaP-HMP gel yield (88.83%) were 50 °C, 40 min and pH 9.6, and for the highest calcium content (97.23 mg g-1 ) they were 40 °C, 30 min and pH 9.7. DC-pectin was a typical LMP with DE varying from 26.92% to 50.33%. The DE of DC-pectin could be predicted by a model that proved significant (R2  = 0.9888). CONCLUSION: The optimum conditions were established to produce CaP gels from HMP with high yield and calcium content. Also, LMP with predictable DE can be produced following a significant model. This study provides new insights into the production and application of CaP gel. © 2021 Society of Chemical Industry.

Buriti Oil Emulsions as Affected by Soy Protein Isolate/High-Methoxyl Pectin Ratio, Oil Content and Homogenization Pressure.

RESEARCH BACKGROUND: Emulsion technology is a suitable way of encapsulating, protecting and releasing hydrophobic bioactive compounds for application in food industries, but they are thermodynamically unstable systems. Good results have been achieved for emulsions stabilized by protein-polysaccharide complexes subjected to high-pressure homogenization. Improved stabilization of oil-in-water emulsions results from electrostatic complexes formed between proteins and polysaccharides at pH lower than the protein isoelectric point, which adsorb at the oil-water interface. In addition, polysaccharides contribute to emulsion stability by increasing viscosity of the continuous phase. The aim of this work is to investigate the production of carotenoid-rich buriti oil emulsions using soy protein isolate and high-methoxyl pectin as stabilizers. EXPERIMENTAL APPROACH: Using a rotatable central composite experimental design, we assessed the effects of oil content, soy protein isolate/high-methoxyl pectin ratio and homogenization pressure on the stability, droplet size, electrical conductivity, electrical charge, microstructure and rheological behaviour of the emulsions. RESULTS AND CONCLUSIONS: An optimized emulsion was produced with 28% buriti oil, 55% soy protein isolate, and homogenization pressure of 380·105 Pa. This emulsion was stable for at least seven days, presenting reduced average droplet size, low electrical conductivity and high modulus of negative charges. The mechanical spectra showed that the emulsion behaved as a viscoelastic gel under oscillatory, non-destructive shearing, whereas shear-thinning behaviour took place under steady shear conditions. NOVELTY AND SCIENTIFIC CONTRIBUTION: The optimized buriti oil emulsions stabilized by soy protein isolate and high-methoxyl pectin could be suitable for fat substitution, energy reduction and carotenoid enrichment in food products, such as dairy and bakery products, ice cream, salad sauces and vegetable-based cream.

Sucrose and Ca2+ synergistically regulate the rheological properties of apple high-methoxyl pectin.

The thickening and gelling mechanism of high-methoxyl pectins (HMPs) with different degree of esterification (DE) values (60.6 %, 66.1 %, and 72.4 %) synergistically affected by calcium ion (Ca2+) and sucrose was investigated using several technical methods. Rheological measurements, including steady-shear flow, thixotropy and dynamic viscoelasticity tests, texture analysis, water-holding capacity (WHC), thermal analyses (TG), and microstructure observation (TEM), were all systemically conducted. The results showed that the main thickening and gelling mechanism of Ca2+ on different HMPs was complex and the presence of sucrose had a synergistic effect on structure formation in HMP systems. Ca2+ was not always conducive to structure formation, and excessive Ca2+ addition may hinder structure formation. HMP systems with lower DE values had higher gel strengths due to the presence of more binding domains. The results of the texture properties, WHC, and thermal characteristics coincided with those obtained from the rheological measurements, which reflect the variations in HMPs affected by Ca2+ and DE. All of these results showed that Ca2+ addition at an appropriate concentration in the presence of sucrose favors HMP gelation even in the absence of acid. The results obtained here are expected to broaden the application of HMPs in acid-free gel food products.

Fabrication and Characterization of Docosahexaenoic Acid Algal Oil Pickering Emulsions Stabilized Using the Whey Protein Isolate-High-Methoxyl Pectin Complex.

In this study, the whey protein isolate-high-methoxyl pectin (WPI-HMP) complex prepared by electrostatic interaction was utilized as an emulsifier in the preparation of docosahexaenoic acid (DHA) algal oils in order to improve their physicochemical properties and oxidation stability. The results showed that the emulsions stabilized using the WPI-HMP complex across varying oil-phase volume fractions (30-70%) exhibited consistent particle size and enhanced stability compared to emulsions stabilized solely using WPI or HMP at different ionic concentrations and heating temperatures. Furthermore, DHA algal oil emulsions stabilized using the WPI-HMP complex also showed superior storage stability, as they exhibited no discernible emulsification or oil droplet overflow and the particle size variation remained relatively minor throughout the storage at 25 °C for 30 days. The accelerated oxidation of the emulsions was assessed by measuring the rate of DHA loss, lipid hydroperoxide levels, and malondialdehyde levels. Emulsions stabilized using the WPI-HMP complex exhibited a lower rate of DHA loss and reduced levels of lipid hydroperoxides and malondialdehyde. This indicated that WPI-HMP-stabilized Pickering emulsions exhibit a greater rate of DHA retention. The excellent stability of these emulsions could prove valuable in food processing for DHA nutritional enhancement.

Effect of apple high-methoxyl pectin on heat-induced gelation of silver carp myofibrillar protein.

The effect of adding apple high-methoxy pectin (HMP) (0-3 mg∙mL-1) on heat-induced gel characteristics of low concentration silver carp myofibrillar protein (MP) (15 mg∙mL-1) was studied. It was found that the hardness of gel increased by 20.6 times with adding 2 mg∙mL-1 HMP. Besides, HMP aided in the development of disulfide bonds and the aggregation of hydrophobic groups. During gel formation, the maximal storage modulus (G') of samples supplemented with 2 mg·mL-1 HMP was raised by a factor of 2.7. Of note, the images of SEM showed that protein and water were tightly combined with a proper amount of HMP and made its pores more uniform and dense. Meantime, the addition of moderate amounts of HMP enabled the formation of gels with favorable texture and performance at low concentration of MP was identified, which could provide a theoretical reference for the design and production of flesh low-calorie food gel.

Effects of different solid particle sizes on oat protein isolate and pectin particle-stabilized Pickering emulsions and their use as delivery systems.

Oat protein isolate (OPI)/high methoxyl pectin (HMP) complexes (OPP) were prepared to stabilized Pickering emulsions and applied as nutraceutical delivery systems. The different mass ratios and pH changed the interactions between OPI and HMP that caused the different size of OPP. Specifically, smaller particle size of OPP (125.7-297.6 nm) were formed when hydrophobic interactions along with electrostatic forces predominant in OPP (OPI:HMP = 3:1, pH 4, 5). Among these particles, OPP-2 could stabilize Pickering emulsion efficiently through formation of dense interfacial film, which exhibited the highest apparent viscosity and the smallest average droplet size (23.39 µm). Moreover, OPP-2 stabilized Pickering emulsions with superior stability not only exhibited higher encapsulation efficiency of 85.63%, but also could control curcumin release in simulated gastrointestinal fluids to improve curcumin's bioaccessibility. These results verified the possibility of OPP to be a Pickering emulsions stabilizer, and also identified its potential to be a stable delivery system for bioactive compounds.

Preparation and characterization of high-methoxyl pectin/glycerides emulsion for pH-responsive, targeting, and sustained release of fat-soluble substances.

In this study, a pH-responsive emulsion system was prepared, combining high-methoxyl pectin (HMP) with camellia oil glycerides (CG). The emulsion was characterized as O/W type, with HMP serving as the wall material and CG as the oil phase. The physicochemical properties, pH responsiveness, digestion stability, and encapsulated delivery capabilities of the HMP-CG emulsion were investigated. The emulsion showed an average droplet size of 480.47 ± 76.19 nm, possessing a negative charge and a pronounced core-shell structure. HMP package CG enhanced hydrophilic ability and enabled targeted release within the small intestine through the structural changes of HMP. The presence of HMP and CG increased droplet dispersion and target digestibility of the emulsion system, leading to sustainable small intestine-specific release. Overall, HMP-CG emulsion system, composed of natural materials, exhibited the ability to achieve targeted and controllable release via pH-responsive mechanisms, offering an alternative for developing gel materials incorporating fat-soluble substances.

Pectin Microwave Assisted Extraction from Pumpkin Peels: Process Optimization and Chemical-Physical and Rheological Characterization.

Recently, pectin, a versatile polysaccharide with different industrial applications, has gained significant attention as an eco-friendly and functional ingredient. This study investigates pumpkin peels (Cucurbita maxima L., Mantua variety) as a novel source of pectin, using a microwave-assisted extraction method with citric acid-acidified water as solvent. The extraction conditions were optimized using a Design of Experiments approach, considering the solvent-to-solid ratio (SSR), pH, temperature, and extraction time. The optimized conditions (94.8 °C, 5 min, pH 1.5, and 46 mL/g SSR) resulted in a pectin yield of 18.05%. A comprehensive characterization of the extracted pectin was performed, including FT-IR spectroscopy, DSC, TGA, rheological properties, and techno-functional assessments such as water holding capacity and fat binding capacity. The results indicated a high degree of esterification (56.19 ± 0.87%), classifying the pumpkin peels (PP) extract as a high methoxyl pectin. PP pectin demonstrated potential as a stabilizer and emulsifying agent, although its high methoxyl content limits its use as a carrier for targeted bioactive delivery. The findings support the viability of using agricultural by-products to obtain valuable polysaccharides, contributing to waste valorization and sustainable industrial practices.

Effect of enzymatic de-esterification and RG-I degradation of high methoxyl pectin (HMP) on sugar-acid gel properties.

The influence of RG-I domains on high methoxyl pectin (HMP) sugar-acid gel properties has rarely been reported. In our work, HMP was modified by enzymatic de-esterification and degradation of RG-I domains to compare and analyze the relationship between the structure and final sugar-acid gel properties. The results showed that the degree of esterification (DE) of REP (pectin degraded by rhamnosidase) and GEP (pectin debranched by galactosidase) was the same as that of untreated HMP, whereas the DE of PMEP (pectin de-esterified by pectin methyl esterase) decreased from 59.63 % to 54.69 %. The monosaccharide composition suggested no significant changes in the HG and RG-I structural domains of PMEP. In contrast, the percentage of RG-I structural domains of REP and GEP dropped from 37 % to about 28 %, accompanied by a reduction in the proportion of the RG-I backbones and side chains. The rheological characterization of sugar-acid gels demonstrated an enhanced gel grade for PMEP and a weakened one for REP and GEP. Moreover, we constructed a correlation relationship between the fine structure of pectin and the properties of the sugar-acid gels, confirming the critical contribution of the RG-I region (especially the neutral sugar side chains) to the HMP sugar-acid gels.

Structural, chemical and technofunctional properties pectin modification by green and novel intermediate frequency ultrasound procedure.

The impact of intermediate frequency ultrasound (IFUS, 582, 864 and 1144 kHz), mode of operation (continue and pulsed) and ascorbic acid (Aa) addition on the structural, chemical and technofunctional properties of commercial citrus high methoxyl-grade pectin (HMP) was investigated. The chemical dosimetry of IFUS, monitored by the triiodide formation rate (I3-), demonstrated that the pulsed ratio (1900 ms on/100 ms off) at the three frequencies was similar to that of continue mode but IFUS1144 kHz produced more acoustic streaming demonstrated by the height liquid measured using image analysis. In presence of Aa, HMP presented higher fragmentation than in its absence. IFUS did not give rise any changes in the main functional groups of the HMP. In general, a reduction in molecular weight was observed, being the presence of Aa the most influencing factor. Regarding monosaccharides, IFUS modified the structure of homogalacturonan and rhamnogalacturonan-I and increased of GalA contents of the HMP in presence of Aa at the above three frequencies. A reducing of the consistency index (k) and increasing of the flow index (n) of HMP were showed by IFUS frequency and Aa addition. The emulsifying activity and stability index were increased for HMP treated by IFUS in continue mode at all frequencies and in presence of Aa. The results presented in this research shown the effectiveness of IFUS as tool to modify pectin into different structures with different functionalities.

Effects of pectin methyl-esterification on intestinal microbiota and its immunomodulatory properties in naive mice.

Pectins are dietary fibers that are attributed with several beneficial immunomodulatory effects. Depending on the degree of esterification (DE), pectins can be classified as high methoxyl pectin (HMP) or low methoxyl pectin (LMP). The aim of this study was to investigate the effects of pectin methyl-esterification on intestinal microbiota and its immunomodulatory properties in naive mice. Supplementation of the diet with LMP or HMP induced changes in the composition of the intestinal microbiota in mice toward Bacteroides, which was mainly promoted by HMP. Metabolome analysis of stool samples from pectin-fed mice showed a different effect of the two types of pectin on the levels of short-chain fatty acids and bile acids, which was consistent with highly efficient in vivo fermentation of LMP. Analysis of serum antibody levels showed a significant increase in IgG and IgA levels by both pectins, while FACS analysis revealed a decrease of infiltrating inflammatory cells in the intestinal lamina propria by HMP. Our study revealed that the structural properties of the investigated pectins determine fermentability, effects on microbial composition, metabolite production, and modulation of immune responses. Consumption of HMP preferentially altered the gut microbiota and suppressed pro-inflammatory immune responses, suggesting a beneficial role in inflammatory diseases.

Nanoencapsulation of Anthocyanins from Red Cabbage (Brassica oleracea L. var. Capitata f. rubra) through Coacervation of Whey Protein Isolate and Apple High Methoxyl Pectin.

Encapsulation is a valuable strategy to protect and deliver anthocyanins (ACNs), phenolic compounds with outstanding antioxidant capacity but limited stability. In this study, coacervation was used to encapsulate an ACN-rich red cabbage extract (RCE). Two agri-food by-product polymers, whey protein isolate (WPI) and apple high-methoxyl pectin (HMP), were blended at pH 4.0 in a specific ratio to induce the formation of nanoparticles (NPs). The process optimisation yielded a monodispersed population (PDI < 0.200) of negatively charged (-17 mV) NPs with an average diameter of 380 nm. RCE concentration influenced size, charge, and antioxidant capacity in a dose-dependent manner. NPs were also sensitive to pH increases from 4 to 7, showing a progressive breakdown. The encapsulation efficiency was 30%, with the retention of ACNs within the polymeric matrix being influenced by their chemical structure: diacylated and/or C3-triglucoside forms were more efficiently encapsulated than monoacylated C3-diglucosides. In conclusion, we report a promising, simple, and sustainable method to produce monodispersed NPs for ACN encapsulation and delivery. Evidence of differential binding of ACNs to NPs, dependent on specific acylation/glycosylation patterns, indicates that care must be taken in the choice of the appropriate NP formulation for the encapsulation of phenolic compounds.

Effects of Calcium and pH on Rheological Thermal Resistance of Composite Xanthan Gum and High-Methoxyl Apple Pectin Matrices Featuring Dysphagia-Friendly Consistency.

High-methoxyl apple pectin (AP) derived from apple was employed as the main ingredient facilitating rheological modification features in developing dysphagia-friendly fluidized alimentary matrices. Xanthan gum (XG) was also included as a composite counterpart to modify the viscoelastic properties of the thickened system under different thermal processes. The results indicate that AP is extremely sensitive to thermal processing, and the viscosity is greatly depleted under a neutral pH level. Moreover, the inclusion of calcium ions echoed the modification effect on the rheological properties of AP, and both the elastic property and viscosity value were promoted after thermal processing. The modification effect of viscoelastic properties (G' and G″) was observed whne XG was incorporated into the composite formula. Increasing the XG ratio from 7:3 to 6:4 (AP:XG) triggers the rheological transformation from a liquid-like form to a solid-like state, and the viscosity value shows that the AP-XG composite system exhibits better thermal stability after thermal processing. The ambient modifiers of pH (pH < 4) and calcium chloride concentration (7.5%) with an optimal AP-XG ratio of 7:3 led to weak-gel-like behavior (G″ < G'), helping to maintain the texture properties of dysphagia-friendly features similar to those prior to the thermal processing.

High methoxyl pectin can improve the extrusion characteristics and increase the dietary fiber content of starch-cellulose extrudates.

Improving total dietary fiber content while maintaining the texture/expansion of extruded products is a challenge. Pectin has a dual function; it is a source of dietary fiber and it also functions as a hydrocolloid, which could improve the texture of high-fiber extruded foods. The objective of this study was to evaluate the impacts of pectin types from citrus peel on the expansion characteristics of starch-cellulose extrudates. High and low methoxyl pectin (HMP and LMP) was added to the starch-cellulose mixtures and extruded using a twin-screw extruder. The pasting properties of raw mixtures, extrusion properties, microstructure, and dietary fiber contents of the extrudates were studied. The inclusion of HMP in raw material improved the peak viscosity (629.7 ± 8.1 to 754.7 ± 80.1 mPa s) and maintained the final viscosity compared to the control (starch-cellulose mixture alone), unlike LMP. HMP relatively maintained the extrusion process parameters such as torque, back pressure, and specific mechanical energy as the control. Interestingly, the addition of 7% of HMP had a similar expansion ratio (3.41 ± 0.08 to 2.35 ± 0.06) compared to the control (3.46 ± 0.08 to 2.32 ± 0.09) under the extrusion conditions studied. The total dietary fiber content improved from 12.22 ± 0.01% to 18.26 ± 0.63% (w/w). HMP maintained the expansion characteristic of starch-cellulose extrudates and improved its total dietary fiber content relative to LMP. Adding HMP to the mixtures improved the extensibility of the melt, favoring bubble growth and expansion of the starch-cellulose extrudates. Fourier transform infrared spectroscopy data suggested that there could be intermolecular interactions between starch, cellulose, and pectin, but the nature of these interactions needs further investigation. PRACTICAL APPLICATION: The study provides practical information on the influence of the addition of high and low methoxyl pectin on starch-cellulose extrudates. The results can help the industry to produce snack products that are more nutritious but are still well accepted by the consumers.

Correlationship between self-assembly behavior and emulsion stabilization of pea protein-high methoxyl pectin complexes treated with ultrasound at pH 2.0.

This study investigated the effects of ultrasound on the self-assembly behavior of pea protein (PP)-high methoxyl pectin (HMP) complexes at pH 2.0 through transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and intrinsic fluorescence analysis. The emulsion stabilization mechanism of PP-HMP treated with ultrasound (PP-HMP-US) was also elucidated. The results indicated that ultrasound increased the emulsifying activity index (EAI) and emulsifying stability index (ESI) of PP-HMP. Moreover, PP-HMP-US-based emulsions formed small, dispersed oil drops, which were stable during storage. PP-HMP- and PP-HMP-US-based emulsions did not demonstrate any creaming. The TEM results revealed that ultrasound can regulate the self-assembly behavior of PP and HMP to form spherical particles with a core-shell structure. This structure possessed low turbidity, a small particle size, and high absolute zeta potential values. The FTIR and intrinsic fluorescence spectra demonstrated that ultrasound increased the α-helix and ß-sheet contents and exposed the tryptophan groups to more hydrophilic environments. Ultrasound also promoted the PP-HMP self-assembly through electrostatic interaction and improved its oil-water interfacial behavior, as indicated by the EAI and ESI values of PP-HMP-US-based emulsions. The current results provide a reference for the development of an innovative emulsifier prepared by ultrasound-treated protein-pectin complexes at low pH.

The droplet breakup model and characteristics of pH-shifted peanut protein isolate-high methoxyl pectin stabilised emulsions under ultrasound.

The effect of pH on the occurrence states of peanut protein isolate (PPI) and high methoxyl pectin (HMP), and droplet breakup model of the emulsions under ultrasound were studied. Particle size distribution and scanning electron microscopy results showed that PPI-HMP existed a soluble complex at pH 5.0, had no interaction at pH 7.0, and was co-soluble at pH 9.0. Droplet breakup model results revealed that the characteristics of emulsion stabilised by PPI-HMP treated at pH 5.0 was different from that at pH 7.0 and 9.0. The average diameter of the droplet well satisfied the model. According to rheological properties, interface tension, and microstructure, the formation mechanism and characteristics of emulsion stabilised by PPI-HMP treated at pH 5.0 was different from that at pH 7.0 and pH 9.0. The research provided a reference for constructing emulsions using pH-shifted PPI-HMP under ultrasound.

The gelation behavior of thiolated citrus high-methoxyl pectin induced by sodium phosphate dibasic dodecahydrate.

The present study found that sodium phosphate dibasic dodecahydrate (Na2HPO4) was capable of inducing the gelation of thiolated citrus high-methoxyl pectin (TCHMP). TCHMP was synthesized by amidation of citrus high-methoxyl pectin. The gel formation exhibited an obvious concentration-dependence, including TCHMP and Na2HPO4 concentration. For Na2HPO4-induced TCHMP gels (TCHMPGs), gel strength and water holding capacity (WHC) increased, while the microcellular network structure was more compact with the increase of TCHMP and Na2HPO4 concentration. Dynamic viscoelastic experiment showed when Na2HPO4 concentration was more than or equal to 0.5 mol/L, TCHMP sols could be transferred into gels within 30 min. Crystal property was not changed while thermal stability was improved after phase transition. Gelling forces analysis indicated that disulfide bonds were the main interaction forces in TCHMPGs. Consequently, TCHMPGs were covalently crosslinked and exhibited satisfactory gel performance. The results provide a theoretical basis for the formation of gels by Na2HPO4 induced TCHMP.