Selective Complex Coacervation of Pea Whey Proteins with Chitosan To Purify Main 2S Albumins

Morphology, surface characteristics and tribological properties of whey protein/chitosan composite particles and their fat replacing effect in O/W emulsion

Whey protein isolate (WPI) and chitosan were used to fabricate WPI/chitosan composite particles at temperatures of 75 °C (WPI/chitosan-75) and 95 °C (WPI/chitosan-95). The morphologic structure, surface properties, and the resulting tribological characteristics of the particles were investigated. The composite particles showed larger particle size than pure WPI particles (WPI-75) (~ 509 nm), with WPI/chitosan-95 the largest (932 nm). WPI/chitosan-75 showed complete core-shell structure from microstructure results. The dispersion of WPI/chitosan-75 exhibited higher surface hydrophobicity but lower viscosity compared to WPI/chitosan-95. Tribological analysis revealed that WPI/chitosan composite particles showed dramatically lower friction coefficient (μ) than pure WPI particles at sliding speed <10 mm/s and WPI/chitosan-75 demonstrated superior lubrication effects. With the presence of artificial saliva, the μ of WPI-75 was greatly lowered at sliding speed <16 mm/s, while the values of WPI/chitosan-75 only showed a slight decrease at sliding speed <1 mm/s. Chitosan might have played the similar role as artificial saliva in lubricating on the hydrophobic surface. Moreover, the incorporation of 0.5 % WPI/chitosan-75 in the low-fat (5 %) oil-in-water emulsion led to even lower μ than full-fat (20 %) emulsion at sliding speed <10 mm/s. Hence, WPI/chitosan-75 exhibited promising potential as a fat replacement and biolubricant.

Properties of Heat-Assisted pH Shifting and Compounded Chitosan from Insoluble Rice Peptide Precipitate and Its Application in the Curcumin-Loaded Pickering Emulsions

Curcumin exhibits antioxidant and antitumor properties, but its poor chemical stability limits its application. Insoluble peptide precipitates formed by proteolysis of rice glutelin are usually discarded, resulting in resource waste. The coupled treatment of heat-assisted pH shifting and compounded chitosan (CS) was used to fabricate rice peptide aggregate-chitosan complexes (RPA-CS). The structure, interfacial behavior, emulsion properties, and digestibility of curcumin-loaded RPA-CS Pickering emulsions were investigated. Increasing the CS concentration led to lower interfacial tension but larger particle size, and the three-phase contact angle of the RPA-CS complexes approached 90°. Quartz crystal microbalance with dissipation (QCM-D) indicated that RPA-CS complexes with 6 g·kg-1 of CS (RPA-CS6) had the highest K1 (0.592 × 106 Hz-1) and K4 (0.487 × 106 Hz-1), suggesting that the softest interfacial layers were formed. The solid-liquid balance of RPA-RPA-CS emulsions was lower than 0.5, declaring that they had more elastic behavior than that of RPA emulsions. RPA-RPA-CS4-and RPA-CS6 emulsions had better storage stability, lower FFA release (79.8% and 76.3%, respectively), and higher curcumin bioaccessibility (65.2% and 68.2%, respectively) than RPA emulsions. This study showed that a low-value insoluble rice peptide precipitate could be used as a valuable emulsifier in foods, which may increase the economics and sustainability of the food supply.

Protein separation by sequential selective complex coacervation

In food manufacturing and particular biomedical products selected proteins are often required. Obtaining the desired proteins in a pure form from natural resources is therefore important, but often very challenging. Herein, we design a sequential coacervation process that allows to efficiently isolate and purify proteins with different isoelectric points (pIs) from a mixed solution, namely Bovine Serum Albumin (BSA, pI = 4.9) and Peroxidase from Horseradish (HRP, pI = 7.2). The key to separation is introducing a suitable polyelectrolyte that causes selective complex coacervation at appropriate pH and ionic strength. Specifically, polyethyleneimine (PEI), when added into the mixture at pH 6.0, produces a coacervation which exclusively contains BSA, leading to a supernatant solution containing 100 % HRP with a purity of 91 %. After separating the dilute and dense phases, BSA is recovered by adding poly(acrylic acid) (PAA) to the concentrated phase, which displaces BSA from the complex because it interacts more strongly with PEI. The supernatant phase after this step contains approximately 75 % of the initial amount of BSA with a purity of 99 %. Our results confirm that coacervation under well-defined conditions can be selective, enabling separation of proteins with adequate purity. Therefore, the established approach demonstrates a facile and sustainable strategy with potential for protein separation at industrial scale.

Quantifying the effects of pre-roasting on structural and functional properties of yellow pea proteins

Roasting could modify the protein structure/conformation, contributing to changes in functional properties. Here we investigated the effects of pre-roasting on the extraction efficiency, structural and functional properties of pea protein concentrates and isolates (PPC and PPI) produced from yellow split peas. The shorter roasting times (150 °C, 10 and 20 min) had little effect on protein yields and could increase the solubility of PPC or PPI by ∼ 12% at pH 7 and enhance the solubility of PPI by ∼ 12% (10-min roasting) and ∼ 24% (20-min roasting) at pH 3. However, a longer duration of pre-roasting (150 °C, 30 min) significantly reduced the extraction efficiency of PPC and PPI by ∼ 30% and ∼ 61%, respectively. Meanwhile, pre-roasting had minor effects on SDS-PAGE profiles and the secondary structures of pea proteins but significantly altered tertiary structures by reducing free sulfhydryl groups, increasing disulfide bonds and surface hydrophobicity. As for the emulsifying properties, pre-roasting improved the emulsion ability index (EAI) of PPC and PPI but decreased the emulsion stability index (ESI) of PPC and had no significant effect on PPI. Moreover, PPC and PPI with shorter pre-roasting duration (10 and 20 min) had endothermic peaks and showed a slight decrease in the denaturation temperature (Td) and the onset temperature (To), respectively. Overall, the study demonstrated that controlled pre-roasting at 150 °C for 10 min and 20 min altered protein structures (mainly tertiary structures), improving the solubility and EAI of pea proteins at pH 7, while retaining their thermal properties in comparison to unroasted samples.

Systematic study on lysozyme-hyaluronan complexes: Multi-spectroscopic characterization and molecular dynamics simulation

This study systematically investigated the complexation mechanism of lysozyme (LYS) and hyaluronan (HA) as well as their complex-formation process using multi-spectroscopy combined with molecular dynamics simulation. Overall, the results demonstrated that electrostatic interaction provides the primary self-assembly driving forces for LYS-HA complex formation. Circular dichroism spectroscopy revealed that the LYS-HA complexes formation primarily alters the α-helix and β-sheet structures of LYS. Fluorescence spectroscopy yielded an entropy of 0.12 kJ/mol·K and enthalpy of -44.46 kJ/mol for LYS-HA complexes. Molecular dynamics simulation indicated that the amino acid residues of ARG114 in LYS and 4ZB4 in HA contributed most significantly. HT-29 and HCT-116 cell experiments demonstrated that LYS-HA complexes possess excellent biocompatibility. Furthermore, LYS-HA complexes were found to be potentially useful the efficient encapsulation of several insoluble drugs and bioactives. These findings provide new insight into the binding mechanism between LYS and HA, and prove indispensable to promoting the potential application of LYS-HA complexes as bioactive compound delivery systems, emulsion stabilizers, or foaming agents in the 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.

Recovery and Utilization of Pea Albumins as Acidic Emulsion Stabilizer by Complexation with Dextran Sulfate

In this work, pea albumins (PAs) were efficiently recovered by complexation with dextran sulfate (DS), and the emulsifying ability and stability of PA/DS complexes were studied. The largest amounts of PAs (81.25%) were recovered at r = 5:1 and pH_max (pH 3.41) by forming insoluble complexes; and only soluble complexes were formed at r = 2:1 and over the whole pH range (2.0-7.0). The emulsions stabilized by PA/DS soluble complexes remained stable under acidic conditions due to the highly negatively charge (from -45.10 ± 0.40 to -57.23 ± 0.66 mV) and small particle size (0.168 ± 0.010-0.448 ± 0.004 μm), while emulsions stabilized by PAs alone generated a strong creaming and serum separation at pH 5 and 6. In terms of emulsifying stability, all PA emulsions and unheated PA/DS emulsions became unstable with different creaming index after 14 days storage. SDS-PAGE results showed that the interface adsorption proteins of unheated emulsions mainly consisted of PA1a, which was unfavorable to the stability of the interface. On the contrary, heat treatment (95 °C, 30 min) and complexation (PA/DS = 2:1) enhanced the adsorption of PA2 and lectin at the interface, inhibiting the aggregation of PA2 and lectin. This resulted in long-term stability of the PA/DS emulsions under acidic conditions.

Fabrication and Characterization of Chitosan-Pea Protein Isolate Nanoparticles

Chitosan (CS) and pea protein isolate (PPI) were used as raw materials to prepare nanoparticles. The structures and functional properties of the nanoparticles with three ratios (1:1, 1:2 1:3, CS:PPI) were evaluated. The particle sizes of chitosan-pea protein isolate (CS-PPI) nanoparticles with the ratios of 1:1, 1:2, and 1:3 were 802.95 ± 71.94, 807.10 ± 86.22, and 767.75 ± 110.10 nm, respectively, and there were no significant differences. Through the analysis of turbidity, endogenous fluorescence spectroscopy and Fourier transform infrared spectroscopy, the interaction between CS and PPI was mainly caused by electrostatic mutual attraction and hydrogen bonding. In terms of interface properties, the contact angles of nanoparticles with the ratio of 1:1, 1:2, and 1:3 were 119.2°, 112.3°, and 107.0°, respectively. The emulsifying activity (EAI) of the nanoparticles was related to the proportion of protein. The nanoparticle with the ratio of 1:1 had the highest potential and the best thermal stability. From the observation of their morphology by transmission electron microscopy, it could be seen that the nanoparticles with a ratio of 1:3 were the closest to spherical. This study provides a theoretical basis for the design of CS-PPI nanoparticles and their applications in promoting emulsion stabilization and the delivery of active substances using emulsions.

An Overview of Coacervates: The Special Disperse State of Amphiphilic and Polymeric Materials in Solution

Individual amphiphiles, polymers, and colloidal dispersions influenced by temperature, pH, and environmental conditions or interactions between their oppositely charged pairs in solvent medium often produce solvent-rich and solvent-poor phases in the system. The solvent-poor denser phase found either on the top or the bottom of the system is called coacervate. Coacervates have immense applications in various technological fields. This review comprises a concise introduction, focusing on the types of coacervates, and the influence of different factors in their formation, structures, and stability. In addition, their physicochemical properties, thermodynamics of formation, and uses and multifarious applications are also concisely presented and discussed.

Pea Albumin Attenuates Dextran Sulfate Sodium-Induced Colitis by Regulating NF-κB Signaling and the Intestinal Microbiota in Mice

BACKGROUND

Inflammatory bowel disease remains a global burden with rapidly increasing incidence and prevalence in both industrialized countries and developing countries. In this study, we prepared pea albumin from pea seeds and determined its beneficial effects being anti-inflammatory and on gut microbiota modulation in dextran sulfate sodium (DSS)-challenged mice.

METHOD

Six-week-old C57BL/6N male mice received an equivalent volume (200 μL) of sterile phosphate balanced solution, 0.375, 0.75, or 1.50 g/kg body weight (BW) of pea albumin that was subjected to 2.0% DSS for 7 days to induce colitis. On day 17 of the experiment, all mice were sacrificed after blood sample collection, and colon tissue and colon contents were collected. BW change curve, colon length, myeloperoxidase (MPO) activity, mucus staining, immunofluorescence staining of T cells and macrophages, cytokines, pro-inflammatory genes expression, nuclear factor-κB (NF-κB) and signal transducer, and activator of transcription 3 (STAT3) signaling pathways as well as 16S DNA sequence were measured.

RESULTS

Our results show that pea albumin alleviates DSS-induced BW loss, colon length shortening, enhanced MPO activity, cytokines secretion, mucus deficiency, and inflammatory cell infiltration, as well as enhanced pro-inflammatory genes expression. In addition, the overactivation of NF-κB and STAT3 following DSS exposure is attenuated by pea albumin administration. Of particular interest, pea albumin oral administration restored gut microbiota dysbiosis as evidenced by enhanced α-diversity, restored β-diversity, and promoted relative abundance of Lactobacillus and Lachnospiraceae_NK4A136_group.

CONCLUSION

Taken together, the data provided herein demonstrated that pea albumin plays a protective role in DSS-induced colitis by reducing inflammatory cell infiltration, pro-inflammatory genes expression and pro-inflammatory cytokines release, inactivation of NF-κB signal, and gut microbiota modulation.

Isolation of B-constituent through selective complex coacervation of hordein with ι-carrageenan

The complex behavior of the crude hordein with ι-carrageenan (Car) as a function of pH (11.0-3.0) and Hordein/Car mass ratios (20:1-1:1, w/w) was studied through zeta potential analysis, turbidimetric titration and SDS-PAGE. By preferential binding with Car, B-hordein was isolated from the crude hordein at pH_max (6.2) and Hordein/Car mass ratio of 15:1, which was further confirmed by LC-MS/MS analysis. The results of zeta potential and size of separated B-hordein and C-hordein suggested that the difference in charge density was the main driving force of selective complexation between hordein and Car. Simultaneously, Fourier transform infrared spectroscopy also confirmed the existence of strong electrostatic interaction between B-hordein and Car. Additionally, the more ordered secondary structure of B-hordein at pH_max might be beneficial to its preferential binding with Car. This study further promotes the application of B-hordein in food industry.

Antidiabetic activities of glycoprotein from pea (Pisum sativum L.) in STZ-induced diabetic mice

Polysaccharides have hypoglycemic activity and pea protein has high nutritional value. The purified pea glycoprotein PGP2 has been shown to inhibit the activity of α-glucosidase and α-amylase in previous studies. To study the mechanism of PGP2-induced blood glucose lowering in vivo, this paper established a diabetic mouse model by intraperitoneal injection of STZ and high-fat diet, and evaluated the blood-glucose-lowering activity of the pea component PGP2 at different doses. The results showed that intragastric administration of PGP2 could effectively reduce diabetic weight loss and polyphagia symptoms, reduce fasting blood glucose levels in mice, and improve oral glucose tolerance levels in mice. PGP2 could promote insulin secretion and had a protective effect on mouse organs. After intragastric administration of PGP2 in mice, the serum levels of total cholesterol, triglycerides and low-density lipoprotein decreased. PGP2 up-regulated the gene expression of insulin receptor substrates IRS-1 and IRS-2 in liver tissues, thereby reducing insulin resistance. Based on the above experimental results, PGP2 had good hypoglycemic activity and was expected to be developed as a natural medicine for the treatment of type II diabetes.

Complex coacervates between bovine serum albumin and anionic polysaccharides: formation and characterization

Abstract The comparative study regarding complexes coacervated between Bovine Serum Albumin (BSA) and different polysaccharides, Pectin (PEC) and Gum Acacia (GA), was carried out by evaluating the influence of different ratios (protein:polysaccharide) and sodium chloride (NaCl) concentrations on turbidity and zeta potential. The BSA:PEC complexes were formed in a 10:1 ratio whereas BSA:GA at 3:1. The complexation pH showed different behavior, BSA: PEC complexes exhibited maximum turbidity in a wide pH range (4.9 to 1.5), while BSA: GA had maximum turbidity at pH 3.5. The increase in the concentration of NaCl negatively influenced the complexation. The NaCl concentration of 0.40 mol L-1 suppressed the interaction in BSA:PEC (10:1) and reduced the range formation of BSA:GA (3:1). The Fourier Transform Infrared (FTIR) demonstrated the participation not only of electrostatic interactions, but also of hydrogen bonds in the complexation. This initial study elucidated fundamental aspects about the formation of coacervate complexes between BSA:GA/PEC that assist in directing its application in food products especially, in acidic matrices (pH~4.0) as well as with low concentration of salts, in view of the effect of pH on maximum formation and sensitivity to NaCl. These complexes can be added directly to products in order to add nutritional value or even be used as a new matrix for the encapsulation of bioactive compounds.