Effect of alkaline de-esterified pectin on the complex coacervation with pea protein isolate under different mixing conditions

Efficacy of almond gum for coacervation with whey protein isolate- optimization, functionality and characterization: A comparison with high-methoxyl pectin

Complex coacervates of whey protein isolate (WPI) and two polysaccharides (almond gum (AG) and high methoxyl pectin (HMP)) under the different pHs (2.5-6.0) and biopolymer mass ratios (1:1-6:1) were prepared to achieve the maximum coacervate yield (CY). The optimum pH and mixing ratio to obtain the maximum CY of WPI-AG (75.93 %) and WPI-HMP (53.0 %) coacervates were 4.3 and 2:1, and 3.5 and 3:1, respectively. Although higher serum layers in emulsions stabilized by WPI-AG/HMP coacervates were detected at the 90 °C, remarkable heat stability under processing temperatures was obtained in ex-situ emulsions with both complex coacervates. Significantly more cold-storage and ionic stabilities were observed for emulsions formulated with WPI-AG than WPI-HMP. Peak shifts in FTIR spectra in the WPI-AG coacervate compared to the individual WPI and AG biopolymers revealed strong electrostatic interactions between these biopolymers. The absence of crystalline peaks for AG and HMP in X-ray diffraction (XRD) spectra confirmed the complexation of AG and HMP with WPI. Thermogravimetric and microstructural analyses showed that porous, loose mesh-like WPI-AG coacervates had superior thermal stability and structural integrity compared to WPI-HMP coacervates and individual biopolymers, which evidenced a more gradual weight loss pattern. WPI-AG coacervates would be promising for efficient emulsion-based delivery systems.

Dextran sulfate acting as a chaperone-like component on inhibition of amorphous aggregation and enhancing thermal stability of ovotransferrin

The tendency of ovotransferrin (OVT) to unfold and aggregate under 60 °C severely restricted sterilization temperature during egg processing. Searching for efficient strategies to improve OVT thermal stability is essential for improving egg product quality and processing suitability. Here, we investigated the effect of sulfate polysaccharide (dextran sulfate, DS) on heat-induced aggregation of OVT. We found that DS can effectively suppress amorphous aggregation of OVT at pH 7.0 after heating. Strikingly, the addition of 5 µM DS fully suppressed insoluble aggregates formation of 0.5 mg/mL OVT. Structure analysis confirmed that DS preserves nearly the entire secondary and tertiary structure of OVT during heating. The steric hindrance effect arising from strong electrostatic interactions between OVT and DS, coupled with reduced OVT hydrophobicity, is the underlying mechanism in suppressing protein-protein interactions, thus enhancing thermal stability. These findings suggest DS could act as protein stabilizers and chaperones, enhancing the thermostability of heat-sensitive proteins.

Analysis of non-covalent interaction between β-lactoglobulin and hyaluronic acid under ultrasound-assisted treatment: Conformational structures and interfacial properties

Hyaluronic acid (HA) used as a food ingredient is gaining acceptance and popularity. However, the studies available for the effect of HA concentrations on the properties of β-lactoglobulin (β-LG) were limited. In this study, we investigated that the molecular characterization and functional properties of the complex formed by the non-covalent binding of β-LG and HA, as well as the ultrasound-assisted treatment at acidic pH. The optimal pH and ratio of β-LG/HA were set as 7 and 4:1, respectively. The fluorescence spectroscopy, circular dichroism spectroscopy, and molecular docking results revealed that the addition of HA and ultrasound induced a decrease in random coil and α-helix and an increase in β-sheet contents in β-LG. By the complexation with HA, the thermal stability, freezing stability, and antioxidant properties of β-LG were all improved under ultrasound treatment. The results of the present study can be useful for the modulation of HA based biopolymer complexes and the exploitation as encapsulating or structuring agents in food industry.

Characterization of coacervation behavior between whey protein isolate and gum Arabic: Effects of heat treatment

Currently, the effect of heat treatment on the complex coacervation behavior of whey isolate protein (WPI) with gum arabic (GA) is undiscussed. In this work, the complex coacervation behavior of WPI with or without heat treatment and GA in different environments was investigated. The results showed that coacervates were formed at a mass ratio of 2:1 and a pH of 3.5, which was confirmed by the fluorescence spectroscopy results. Heat treatment increased the surface charge of WPI, reduced the saturated adsorption concentration of GA, and enhanced the sensitivity of the complex coacervation reaction to salt ions. Fourier infrared spectroscopy, intermolecular force analysis and molecular docking results confirm that the formation of coacervates is the result of electrostatic interactions. From the scanning electron microscope and differential scanning calorimetry results, it is clear that the whey isolate protein combined with gum arabic forms a gel-like conjugate with higher thermal stability and a dense structure. This study provides more in-depth theoretical guidance for the application of WPI and GA based coacervation and more advanced theoretical data for the study of hWPI.

Versatile functionalization of pectic conjugate: From design to biomedical applications

Pectin exists extensively in nature and has attracted much attention in biological applications for its unique chemical and physical characteristics. Functionalized pectin, especially pectic conjugates, has given many possibilities for pectin to improve its properties and bioactivity as well as to deliver active molecules. To better exploit this strategy of pectic functionalization, this review presents in detail the structural modifications of pectin, different synthetic methods, and design strategies of pectic conjugates involving both traditional chemical and "green" approaches. Here, the research ideas and applications of pectic prodrugs as well as the development of preparation based on pectic conjugates are reviewed, with emphasis on crosslinking systems of functionalized pectin and nanosystems based on self-assembly techniques. We hope this review will provide comprehensive and valuable information for the functionalization and systematization of the pectic conjugate from synthesis to application.

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 (Mw) 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.

Encapsulation of Vitamin B12 by Complex Coacervation of Whey Protein Concentrate-Pectin; Optimization and Characterization

Vitamin B12 (VB12) is one of the essential vitamins for the body, which is sensitive to light, heat, oxidizing agents, and acidic and alkaline substances. Therefore, the encapsulation of VB12 can be one of the ways to protect it against processing and environmental conditions in food. In this work, the influence of pectin concentration (0.5−1% w/v), whey protein concentrate (WPC) level (4−8% w/v) and pH (3−9) on some properties of VB12-loaded pectin−WPC complex carriers was investigated by response surface methodology (RSM). The findings showed that under optimum conditions (1:6.47, pectin:WPC and pH = 6.6), the encapsulation efficiency (EE), stability, viscosity, particle size and solubility of complex carriers were 80.71%, 85.38%, 39.58 mPa·s, 7.07 µm and 65.86%, respectively. Additionally, the formation of complex coacervate was confirmed by Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). In addition, it was revealed that the most important factor in VB12 encapsulation was pH; at a pH < isoelectric point of WPC (pH = 3), in comparison with higher pH values (6 and 9), a stronger complex was formed between pectin and WPC, which led to an increase in EE, lightness parameter, particle size and water activity, as well as a decrease in the zeta-potential and porosity of complex carriers.

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.

Maillard-Type Protein-Polysaccharide Conjugates and Electrostatic Protein-Polysaccharide Complexes as Delivery Vehicles for Food Bioactive Ingredients: Formation, Types, and Applications

Due to their combination of featured properties, protein and polysaccharide-based carriers show promising potential in food bioactive ingredient encapsulation, protection, and delivery. The formation of protein–polysaccharide complexes and conjugates involves non-covalent interactions and covalent interaction, respectively. The common types of protein–polysaccharide complex/conjugate-based bioactive ingredient delivery systems include emulsion (conventional emulsion, nanoemulsion, multiple emulsion, multilayered emulsion, and Pickering emulsion), microcapsule, hydrogel, and nanoparticle-based delivery systems. This review highlights the applications of protein–polysaccharide-based delivery vehicles in common bioactive ingredients including polyphenols, food proteins, bioactive peptides, carotenoids, vitamins, and minerals. The loaded food bioactive ingredients exhibited enhanced physicochemical stability, bioaccessibility, and sustained release in simulated gastrointestinal digestion. However, limited research has been conducted in determining the in vivo oral bioavailability of encapsulated bioactive compounds. An in vitro simulated gastrointestinal digestion model incorporating gut microbiota and a mucus layer is suggested for future studies.

The viability of complex coacervate encapsulated probiotics during simulated sequential gastrointestinal digestion affected by wall materials and drying methods

The objective of this study was to investigate the impact of protein type (sodium caseinate and pea protein isolate) and protein to sugar beet pectin mixing ratio (5 : 1 and 2 : 1) on complex coacervate formation, as well as the impact of the finishing technology (freeze-drying and spray-drying) for improving the viability of encapsulated Lactobacillus rhamnosus GG (LGG) in complex coacervates during simulated sequential gastrointestinal (GI) digestion. The physicochemical properties of LGG encapsulated microcapsules in liquid and powder form were evaluated. The state diagram and ζ-potential results indicated that pH 3.0 was the optimum pH for coacervate formation in the current systems. Confocal laser scanning microscopy (CLSM), viscoelastic analysis, and Fourier transform infrared spectroscopy (FTIR) confirmed that the gel-like network structure of the complex coacervates was successfully formed between the protein and SBP at pH 3.0 through electrostatic interaction. In terms of physiochemical properties and viability of LGG encapsulated in the microcapsule powder, the drying method played a crucial role on particle size, microstructure and death rate of encapsulated LGG during simulated sequential GI digestion compared to protein type and biopolymer mixing ratio. For example, the microstructure of spray-dried microcapsules exhibited smaller spherical particles with some cavities, whereas the larger particle size of freeze-dried samples showed a porous sponge network structure with larger particle sizes. As a result, spray-dried LGG microcapsules generally had a lower death rate during simulated sequential gastrointestinal digestion compared to their freeze-dried counterparts. Among all samples, spray-dried PPI-SBP microcapsules demonstrated superior performance against cell loss and maintained more than 7.5 log CFU per g viable cells after digestion.

Complex coacervation of pea albumin-pectin and ovalbumin-pectin assessed by isothermal titration calorimeter and turbidimetry

BACKGROUND

This study investigates the complexation of a pea albumin-rich fraction and ovalbumin with pectin of different degrees of esterification (DE) and blockiness (DB) as a function of pH and biopolymer mixing ratio by turbidimetric titration and isothermal titration calorimetry (ITC).

RESULTS

Turbidimetric analysis found maximum complexation occurred at a mixing ratio of 4:1 for pea albumin with high methoxy pectin, 8:1 for pea albumin with low methoxy pectin, and 8:1 for ovalbumin with low methoxy pectin. In the case of ovalbumin with high methoxy pectin, interactions were very weak. The pectin with high levels of esterification and blockiness displayed greater interactions with the pea albumin in both turbidimetry and ITC. However, low methoxy pectin imparted better interactions with ovalbumin and displayed higher optical density values than high methoxy pectin.

CONCLUSIONS

The current study indicated that the different thermodynamic parameters of PA-pectin complexes can be tuned by controlling the structural characteristics (DB, DE, and d-galacturonic acid) of the pectin. © 2020 Society of Chemical Industry.

Effect of different levels of esterification and blockiness of pectin on the functional behaviour of pea protein isolate-pectin complexes

This research examines changes to the functional (solubility, emulsifying and foaming) properties of pea protein isolate when complexed with commercial citrus pectin of different structural attributes. Specifically, a high methoxy (P90; degree of esterification: 90.0%; degree of blockiness: 64.5%; galacturonic acid content 11.4%) and low methoxy (P29; degree of esterification: 28.6%; degree of blockiness: 31.1%; galacturonic acid: 70%) pectin at their optimum mixing ratios with pea protein isolate (4:1 pea protein isolate to P90; 10:1 pea protein isolate to P29) were assessed at the pHs associated with critical structure forming events during the complexation process (soluble complexation (pH_c), pH 6.7 and 6.1; insoluble complex formation (pH_ϕ1), pH 4.0 and 5.0; maximum complexation (pH_opt), pH 3.5 and 3.8; dissolution of complexes, pH 2.4 and 2.1; for admixtures of pea protein isolate-P90 and pea protein isolate-P29, respectively). Pea protein isolate solubility was improved from 41 to 73% by the presence of P90 at pH 6.0 and was also moderately increased at pH 4.0 and pH 5.0 by P90 and P29, respectively. The emulsion stability of both pea protein isolate-pectin complexes was higher than the homogeneous pea protein isolate at all critical pHs except pH_opt as well as pH_c for pea protein isolate-P29 only. P90, with the higher level blockiness and esterification, displayed better foaming properties at the maximal complexation pH when complexed with pea protein isolate than pea protein isolate-P29 or pea protein isolate alone. However at pH_ϕ2, pea protein isolate-P29 admixtures produced foams with 100% stability, increasing pea protein isolate foam stability by 85%. The enhanced functionality of pea protein isolate-pectin complexes based on the type of pectin used at critical pHs indicates they may be useful biopolymer ingredients in plant protein applications.

Development of high methoxyl pectin-surfactant-pea protein isolate ternary complexes: Fabrication, characterization and delivery of resveratrol

The purpose of this study was to fabricate ternary complexes composed of pea protein isolate (PPI), high methoxyl pectin (HMP) and individual surfactants including rhamnolipid (Rha), tea saponin (TS) and Ethyl lauroyl arginate (LAE), for the delivery of resveratrol (Res). A combination of electrostatic attraction and hydrophobic interaction was dominantly responsible for the formation of HMP-surfactant-PPI complexes. The physicochemical properties of the ternary complexes were affected by surfactant types as well as mass ratios of individual surfactant to PPI. HMP-Rha-PPI_1:1, HMP-TS-PPI_1:1 and HMP-LAE-PPI_1:25 complexes had higher denaturation temperatures of 82.78 ± 0.31, 80.21 ± 0.02 and 79.98 ± 0.86 ℃, respectively. The HMP-Rha-PPI_1:1 ternary complex could be an effective delivery system, which were effective to retard photo- and thermal- degradation of Res as well as delayed the release of Res in in vitro digestion.