Effect of pH on the functional behaviour of pea protein isolate–gum Arabic complexes

The health benefits, functional properties, modifications, and applications of pea (Pisum sativum L.) protein: Current status, challenges, and perspectives

In recent years, the development and application of plant proteins have drawn increasing scientific and industrial interests. Pea (Pisum sativum L.) is an important source of high-quality vegetable protein in the human diet. Its protein components are generally considered hypoallergenic, and many studies have highlighted the health benefits associated with the consumption of pea protein. Pea protein and its hydrolysates (pea protein hydrolysates [PPH]) possess health benefits such as antioxidant, antihypertensive, and modulating intestinal bacteria activities, as well as various functional properties, including solubility, water- and oil-holding capacities, and emulsifying, foaming, and gelling properties. However, the application of pea protein in the food system is limited due to its poor functional performances. Several frequently applied modification methods, including physical, chemical, enzymatic, and combined treatments, have been used for pea protein to improve its functional properties and expand its food applications. To date, different applications of pea protein in the food system have been extensively studied, for example, encapsulation for bioactive ingredients, edible films, extruded products and substitution for cereal flours, fats, and animal proteins. This article reviews the current status of the knowledge regarding pea protein, focusing on its health benefits, functional properties, and structural modifications, and comprehensively summarizes its potential applications in the food industry.

Utilization of pulse protein-xanthan gum complexes for foam stabilization: The effect of protein concentrate and isolate at various pH

The present study examines the foaming behavior of pea and faba bean protein concentrates and isolates and explores the impact of pH and protein-polysaccharide complexation on overrun and foam stability. Foams were prepared with 5 wt% proteins with and without 0.25 wt% xanthan gum (XG) at pH 3, 5, 7 and 9. Most foams were unstable without XG. With XG foaming properties of protein concentrates were better than isolates. Irrespective of protein type and content, all protein-XG foams at pH 3 destabilized due to large insoluble complexes, however, at pH 5 foams were stable due to smaller size of insoluble complexes. Both the protein concentrate-XG foams were stable at pH 7 and 9 due to optimum viscosity and surface tension of the soluble complexes. Overall, the study revealed that the overrun and stability of pulse protein foams can be significantly improved by adding XG and controlling their intermolecular interactions as a function of pH.

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.

Characterization and enhanced functionality of nanoparticles based on linseed protein and linseed gum biocomplexes

The formation, characterization, and functionality of hybrid nanoparticles based on linseed bio-macromolecules extracted as linseed protein (LP) and linseed gum (LG) from the remaining meal after oil extraction were investigated. The assembly of bioparticles at different protein to polysaccharide ratios as a function of pH was characterized in terms of absorbance measurements, dynamic light scattering and surface charge. The wettability of the assembled particles as well as the plain LP and LG was also determined. By increasing the LG proportion in the bioparticles, both the size of the particles and their contact angle tended to decrease, whereas their zeta potential became more negative over the whole studied pH range. The formed negatively charged particles at pH 3 with a 50:50 LP to LG ratio and a size of approximately 300 nm were selected and their functional properties (solubility, emulsifying and foaming properties) were compared to the individual biopolymers. The interaction between LG and LP was found to modify the functional properties of native LP especially at and around its isoelectric point. The LP-LG particles could be useful for stabilizing plant-based emulsions and foams.

Impacts of short-term germination on the chemical compositions, technological characteristics and nutritional quality of yellow pea and faba bean flours

In the present study, yellow pea (CDC Amarillo) and faba bean (CDC Snowdrop) seeds were soaked overnight and then germinated in the dark at ambient temperature for 24, 48 and 72 h. During the short-term germination, germination percentages higher than 96.6% were achieved and progressive growth of radicles was observed for both varieties. The soaked and germinated seeds were dried at 55 °C and milled into flours, and their chemical compositions, physicochemical properties and in vitro starch and protein digestibility were systematically examined. Overall, soaking and germination did not noticeably alter the chemical compositions of each flour. The most obvious changes in the physicochemical properties were found in the pasting, emulsifying and foaming properties of the pulse flours. Soaking and 24-h germination greatly enhanced the pasting viscosities of the flours; as the germination proceeded, their viscosities gradually decreased, resulting from the degradation of starch by endogenous amylase(s) during pasting. Germination progressively improved the emulsion activity and stability, foaming capacity and foam stability of both pulse flours. In addition, germination enhanced the in vitro digestibility of starch and protein of the flours; however, the treatment did not improve their in vitro protein digestibility corrected amino acid scores (IV-PDCAAS). Short-term germination of 24-72 h has been demonstrated to be an effective approach to generating pulse flours possessing diverse functional properties and enhanced digestibility of macronutrients.

Formation and Stability of Pea Proteins Nanoparticles Using Ethanol-Induced Desolvation

Protein nanoparticles have recently found a lot of interests due to their unique physicochemical properties and structure-functionality compared to the conventional proteins. The aim of this research was to synthesize pea protein nanoparticles (PPN) using ethanol-induced desolvation, to determine the changes in secondary structures and the particle stability in an aqueous dispersion. The nanoparticles were prepared by diluting 3.0 wt% pea protein solutions in 1-5 times ethanol at pH 3 and 10 at different temperatures. Higher ratios of ethanol caused greater extent of desolvation and larger sizes of PPN. After homogenization at 5000 psi for 5 min, PPN displayed uniform size distribution with a smaller size and higher zeta potential at pH 10 compared to pH 3. PPN prepared from a preliminary thermal treatment at 95 °C revealed a smaller size than those synthesized at 25 °C. Electron microscopy showed roughly spherical shape and extensively aggregated state of the nanoparticles. Addition of ethanol caused a reduction in β-sheets and an increase in α-helices and random coil structures of the proteins. When PPN were separated from ethanol and re-dispersed in deionized water (pH 7), they were stable over four weeks, although some solubilization of proteins leading to a loss in particle size was observed.

Protein quality and physicochemical properties of commercial cricket and mealworm powders

The pressing need for protein supply growth gives rise to alternative protein sources, such as insect proteins. Commercial cricket and mealworm powders were examined for their protein quality, surface charge and functional attributes. Both insect powders had similar proximate compositions with protein and ash contents of ~ 66% db (dry weight basis) and 5% db, respectively, however cricket powder contained more lipid (16.1%, db) than mealworm powder (13.7%, db). Mealworm protein had an amino acid score of 0.71 and was first limiting in lysine, whereas cricket protein was first limiting in tryptophan with an amino acid score of 0.85. In vitro protein digestibility values of 75.7% and 76.2%, and in vitro protein digestibility corrected amino acid scores of 0.54 and 0.65, were obtained for mealworm and cricket powders, respectively. Zeta potential measurements gave isoelectric points near pH 3.9 for both insect powders. Mealworm and cricket powders had water hydration capacities of 1.62 g/g and 1.76 g/g, respectively, and oil holding capacities of 1.58 g/g and 1.42 g/g, respectively. Both insect proteins had low solubility (22-30%) at all pHs (3.0, 5.0, and 7.0) measured. Cricket powder had a foaming capacity of 82% and foam stability of 86%, whereas mealworm powder was non-foaming. Values for commercial pea and faba bean protein concentrates were reported for comparative purposes. The insect proteins had similar protein quality as the pulse proteins and had higher solubility at pH 5.0 but were much less soluble at pH 7.0.

Effect of electron beam irradiation on the structural characteristics and functional properties of rice proteins

A study of the structural and functional changes of rice proteins (RPs) induced by electron beam irradiation (EBI) at 5 kGy, 10 kGy, 20 kGy, and 30 kGy was performed. The microcosmic surface structures of the RPs were changed and fragmented due to irradiation damage occurring on the RP surfaces. The changes in the UV visible spectra, intrinsic fluorescence spectra, surface hydrophobicity and SH and SS group contents indicated that the RPs unfolded after EBI treatment. In addition, the degree of conformational change was increased with increasing EBI treatment doses. FTIR analysis showed that the secondary structure redistributed, showing decreases in α-helices and concomitant increases in β-sheets, β-turns and random coils. The functional properties, emulsifying abilities, water adsorption capacities and oil adsorption capacities of the irradiated RPs improved dose-dependently, with maximums occurring at 30 kGy. The foaming properties were also enhanced by EBI; however, this effect was not dose-dependent. In contrast, all of the samples irradiated by electron beams presented lower emulsion stability than the control (0 kGy). These results provide a theoretical basis for the application of EBI in improving protein properties in the future.

Kinetic studies on palm heart protein solubility and investigation of physicochemical, functional and thermal properties of palm heart protein isolate

The chemical composition of palm heart (cultivar Piarom) and solubility kinetics of its protein was investigated under different salt concentrations and pHs. Palm heart protein isolate (PHPI) was prepared using alkaline extraction and acidic precipitation and its functional properties (emulsifying properties and emulsion stability, foam capacity, and water holding and fat absorption capacity) and thermal properties were determined. It was revealed that palm heart had high nutritional value and contains high protein content. By increasing pH up to 3, solubility was decreased and then significantly increased by elevating pH to 9 (p < 0.05). Salt addition significantly decreased palm heart protein (PHP) solubility. Considering solubility kinetics, pH  9 and salt concentration of 0.25 M was determined as the best protein extraction condition. Denaturation temperature and enthalpy changes of PHPI were 108.63 °C and 143.1 J/g; suggesting high thermal stability of this product. Regarding its suitable functional, physicochemical and thermal properties, PHP can be considered as an ideal substitution for animal protein sources in the food industry.

Designing biopolymer-coated Pickering emulsions to modulate in vitro gastric digestion: a static model study

The aim of this study was to restrict the degree of gastric destabilization of Pickering emulsions by using electrostatic deposition of a biopolymeric layer at the proteinaceous particle–laden oil–water interface.

Review on plant protein-polysaccharide complex coacervation, and the functionality and applicability of formed complexes

Controlling the interactions between plant proteins and polysaccharides can lead to the development of novel electrostatic complexed structures that can give unique functionality. This in turn can broaden the diversity of applications that they may be suitable for. Overwhelmingly in the literature, work and reviews relating to coacervation have involved the use of animal proteins. However, with the increasing demand for plant-based protein alternatives by industry and consumers, a greater understanding of how they interact with polysaccharides is essential to control structure, functionality and applicability. This review discusses the factors governing the nature of protein-polysaccharide interactions, their functional attributes and industrial applications, with special attention given to plant proteins. © 2018 Society of Chemical Industry.

Effect of the degree of esterification and blockiness on the complex coacervation of pea protein isolate and commercial pectic polysaccharides

The complex coacervation of pea protein isolate (PPI) with commercial pectic polysaccharides [high methoxy citrus pectin (P90, 90 representing DE), apple pectin (P78) sugar beet pectin (P62), low methoxy citrus pectin (P29)] of different degrees of esterification (DE) [and galacturonic acid content (GalA)] and blockiness (DB), was investigated. The maximum amount of coacervates formed at a biopolymer weight mixing ratio of 4:1 for all PPI-pectin mixtures, with the exception of PPI-P29 where maximum coacervation occurred at the 10:1 mixing ratio. The pH at which maximum interactions occurred was pH 3.4-3.5 (PPI: P90/P78) and 3.7-3.8 (PPI: P62/P29). PPI complexed with pectins with high levels of DE (low levels of GalA) and DB displayed greater interactions at optimal mixing conditions compared to pectin having lower levels of esterification and blockiness. The addition of P78 to PPI greatly increased protein solubility at pH 4.5.

Reduction of off-flavours and the impact on the functionalities of lentil protein isolate by acetone, ethanol, and isopropanol treatments

The changes of flavour profiles in lentil protein isolate (LPI) in response to organic solvent treatments (acetone, ethanol, and isopropanol; 35-95% v/v), and the resulting impacts on the isolate colour and physicochemical and functional attributes were investigated. The major constituents of volatile compounds were aldehydes (∼46.59%) and (E,E)-3,5-octadien-2-one (∼31.79%) in the untreated LPI. Acetone treatment greatly raised ketones by ∼79.59%. In contrast, ethanol and isopropanol, except at 95% (v/v), significantly lowered total volatile compounds and had higher protein contents (∼84.55%) than the others (∼76.98%); surface charge, surface hydrophobicity, solubility and emulsion stability of these LPIs were examined. LPIs obtained from 75% (v/v) ethanol and isopropanol treatments showed slightly lower solubility but improved surface hydrophobicity to produce emulsions with a similar stability as compared with the untreated LPI. Overall, ethanol and isopropanol treatments (75% v/v) produced high quality off-flavour-reduced LPIs which may be used in various food systems.

Sericin/RBA embedded gellan gum based smart nanosystem for pH responsive drug delivery

Polysaccharides protein complex offers a green alternative to synthetic polymers in the drug delivery system. Sericin (SC), a natural protein, in combination with rice bran albumin (RBA) and gellan gum (GG) forms a green based protein polysaccharide complex. The sericin functionalized gellan gum-rice bran (SC-GG-RBA) nanocomposites were characterized by different characterization techniques. It shows their prominent ability in balancing the biocompatibility, stability, biodegradability, and functionality of nanocarriers. The nanocomposites exhibited spherical shape with core protein-polysaccharide structures, and the average size was about 218 nm. High amount of Doxorubicin (DOX) was encapsulated into SC-GG-RBA nanocomposites in order to investigate the effective drug release in acidic tumor environment. DOX of 84% was released in vitro condition after 120 h in pH 4.0. DOX loaded green nanocomposites shows IC₅₀ 5 μg/mL which was very low compared to free DOX of 9 μg/mL after treatment with MCF-7 cells. Only 42% of cells were survived after treatment with green nanocomposites. This was due to the effective uptake of nanomaterial by cancer cells and direct release of DOX in cytoplasmic region. Such high performance green nanocomposites have great potential in expanding the utilization of biomaterial from natural resources and development of sensible application in biomedical field.

Effect of high intensity ultrasound on structure and foaming properties of pea protein isolate

The effects of high intensity ultrasound (HIUS, 20 kHz, at varying amplitude 30%, 60%, 90% for 30 min) on structure and foaming properties of pea protein isolate (PPI) were investigated. No significant change was observed from the electrophoresis profiles and circular dichroism (CD) spectrum. Analyses of fluorescence spectroscopy and the amount of free sulfhydryl groups showed that HIUS induced protein molecular partial unfolding. Furthermore, HIUS decreased particle size of PPI and increased exposed hydrophobicity, resulting in a reduction of the surface tension at the air-water interface. Therefore, the foaming ability of PPI increased from 145.6% to 200.0%. The foaming stability increased from 58.0% to 73.3% with the increasing amplitude after 10 min though all reduced to 50.0% with the extension of time. That suggested that HIUS treatment has a potential to be implemented to modify foaming properties of PPI.

Influence of surfactants and proteins on the properties of wet edible calcium alginate meat coatings

Calcium alginate structures are of interest as replacers for natural casings due to their high availability, biodegradability and low price. The aim of this paper is to study the effect of oil, surfactants and proteins (pea and collagen) on the water transfer, mechanical and microstructural properties of the wet calcium alginate films. The addition of oil and surfactants tended to reduce the water permeance and the weight loss rate, reaching values between those shown by natural and collagen artificial casings. The addition of proteins did not improve the adherence of the films and it decreased the maximum force of the film at puncture test, which was even lower with the presence of the surfactant E475. The TEM micrographs showed that the differences in mechanical properties are mainly related to the differences in the compaction of the microstructure. Wet alginate films with E475 are envisaged as a substitute of natural and collagen artificial casings in the stuffed meat products industry.

Nanostructure and functionality of enzymatically repolymerized whey protein hydrolysate

Whey proteins (WPI) were polymerized with transglutaminase (TGase) before and after partially hydrolyzing the protein with thermolysin to produce protein nanoparticles/polymers. Electrophoresis and atomic force microscopy (AFM) were used to determine the size and structural characteristics of the polymers. The foaming and emulsifying properties of these nanoparticles were studied. The polymerized WPI (WPI-TG) produced more stable foams than the repolymerized WPI hydrolysate (WPIH-TG). In contrast, WPIH-TG produced better emulsions with better storage stability than WPI-TG emulsions. These differences were due to their structure and electrostatic properties: The WPI-TG particles were linear, less than 100 nm in size with lower net negative charge, whereas the WPIH-TG polymers were much larger and were highly negatively charged as judged from zeta potential. This suggested that while protein nanoparticles may provide Pickering stability to both emulsions and foams, strong lateral electrostatic repulsion between nanoparticles within the adsorbed film destabilizes foams but not emulsions.