Evidence and characterization of complex coacervates containing plant proteins: application to the microencapsulation of oil droplets

Toward Diverse Plant Proteins for Food Innovation

This review highlights the development of plant proteins from a wide variety of sources, as most of the research and development efforts to date have been limited to a few sources including soy, chickpea, wheat, and pea. The native structure of plant proteins during production and their impact on food colloids including emulsions, foams, and gels are considered in relation to their fundamental properties, while highlighting the recent developments in the production and processing technologies with regard to their impacts on the molecular properties and aggregation of the proteins. The ability to quantify structural, morphological, and rheological properties can provide a better understanding of the roles of plant proteins in food systems. The applications of plant proteins as dairy and meat alternatives are discussed from the perspective of food structure formation. Future directions on the processing of plant proteins and potential applications are outlined to encourage the generation of more diverse plant-based products.

Decoding the interaction mechanism between bis(2-methyl-3-furyl) disulfide and oral mucin

The interactions between mucin and aroma compounds have been shown to affect aroma perception. This study aimed to investigate the binding behavior between mucin and bis(2-methyl-3-furyl) disulfide and reveal the interaction mechanism at different pH levels. Based on our results, the binding percentages between mucin and bis(2-methyl-3-furyl) disulfide ranged from 37.03 % to 71.87 % at different contents. The complexes formation between mucin and bis(2-methyl-3-furyl) disulfide was confirmed by turbidity, particle size, zeta-potential, and surface hydrophobicity analyses. According to the results of multispectral techniques and molecular dynamic simulation, mucin could interact with bis(2-methyl-3-furyl) disulfide by hydrogen bonding, hydrophobic interactions, and van der Waals force. Furthermore, the binding constants of mucin to bis(2-methyl-3-furyl) disulfide were 1.26 × 103, 1.14 × 103, and 9.13 × 103 L mol-1 at pH 5.0, 7.0, and 8.5, respectively. These findings contribute to the comprehensive knowledge on the interaction mechanism between bis(2-methyl-3-furyl) disulfide and mucin, providing insights for flavor modulation in meat products.

Simple and complex coacervation in systems involving plant proteins

Plant-based foods are gaining popularity as alternatives to meat and dairy products due to sustainability and health concerns. As a consequence, there is a renewed interest in the phase behaviour of plant proteins and of mixtures of plant proteins and polysaccharides, in particular in the cases where coacervation is found to occur, i.e., liquid-liquid phase separation (LLPS) into two phases, one of which is rich in biopolymers and one of which is poor in biopolymer. Here we review recent research into both simple and complex coacervation in systems involving plant proteins, and their applications in food- as well as other technologies, such as microencapsulation, microgel production, adhesives, biopolymer films, and more.

A comparative study on the encapsulation of black carrot extract in potato protein-pectin complexes

This manuscript reveals the effect of the emulsification step on the black carrot extract (BCE) stabilization by potato protein isolate (PPI)-citrus pectin (CP) coacervates. The effect of core-to-wall ratio and concentration of wall material were also investigated. This was the first attempt to compare the characteristics of emulsified core particles (ECP) and non-emulsified core particles (NECP) coated with complex coacervates. Potato protein was used as an encapsulating agent by complex coacervation for the first time, and it showed excellent characteristics for the encapsulation. Non-hygroscopic particles were produced with emulsification while most of NECPs were slightly hygroscopic. The mean particle diameter of powders ranged from 65.05 to 152.47 μm which is suitable with SEM micrographs. ECPs showed lower particle size values with increased wall concentration at the constant core-to-wall ratio. Encapsulation efficiency (EE) increased, and anthocyanin retention (AR) decreased when emulsification was included. EE of NECP and ECP was between 69.26-82.84% and 85.48-90.15% while AR was between 79.08-102.16% and 53.90-83.37%, respectively. FT-IR and ζ-potential values proved the complexation between PPI and CP in ECPs as well as the interaction of PP, CP, and BCE in NECPs. DSC thermograms proved the success of the encapsulation procedure and thermo-stability of the BCE-loaded particles.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05787-z.

A Review of Biopolymers' Utility as Emulsion Stabilizers

Polysaccharides, polynucleotides, and polypeptides are basic natural polymers. They have various applications based on their properties. This review mostly discusses the application of natural polymers as emulsion stabilizers. Natural emulsion stabilizers are polymers of amino acid, nucleic acid, carbohydrate, etc., which are derived from microorganisms, bacteria, and other organic materials. Plant and animal proteins are basic sources of natural emulsion stabilizers. Pea protein-maltodextrin and lentil protein feature entrapment capacity up to 88%, (1-10% concentrated), zein proteins feature 74-89% entrapment efficiency, soy proteins in various concentrations increase dissolution, retention, and stability to the emulsion and whey proteins, egg proteins, and proteins from all other animals are applicable in membrane formation and encapsulation to stabilize emulsion/nanoemulsion. In pharmaceutical industries, phospholipids, phosphatidyl choline (PC), phosphatidyl ethanol-amine (PE), and phosphatidyl glycerol (PG)-based stabilizers are very effective as emulsion stabilizers. Lecithin (a combination of phospholipids) is used in the cosmetics and food industries. Various factors such as temperature, pH, droplets size, etc. destabilize the emulsion. Therefore, the emulsion stabilizers are used to stabilize, preserve and safely deliver the formulated drugs, also as a preservative in food and stabilizer in cosmetic products. Natural emulsion stabilizers offer great advantages because they are naturally degradable, ecologically effective, non-toxic, easily available in nature, non-carcinogenic, and not harmful to health.

Core-Shell Microcapsules from Unpurified Legume Flours

Plant-based ingredients are key building blocks for future sustainable advanced materials. Functionality is typically higher for highly purified plant-based ingredients, but this is at the expense of their sustainability value. Here, a method is introduced for creating a soft functional material, with structural elements ranging from the nanometer to the millimeter scale, directly from legume flours. Globulins from soy and pea flours are extracted in their native state at acidic pH and mixed with gum arabic, resulting in liquid-liquid phase separation into a dilute phase and a viscoelastic complex coacervate. Interfacial tensions of the coacervates, determined via AFM-based probing of capillary condensation, are found to be very low (γ = 48.5 and 32.3 μN/m for, respectively, soy and pea), thus promoting the deposition of a shell of coacervate material around oil droplets. Despite the complex nature of the starting material, the dependence of interfacial tensions on salt concentrations follows a scaling law previously shown to hold for model complex coacervates. Curing of the coacervate material into a strong and purely elastic hydrogel is shown to be possible via simple heating, both in bulk and as a shell around oil droplets, thus providing proof of principle for the fabrication of precise core-shell microcapsules directly from legume flours.

Elucidating the pH influence on pulsed electric fields-induced self-assembly of chitosan-zein-poly(vinyl alcohol)-polyethylene glycol nanostructured composites

HYPOTHESIS

The high incompatibility of bio-based materials such as protein and polysaccharides require a series of modifications to develop stable microstructures effectively. By modifying the density and charge of surface residues, pulsed electric fields processing can improve inter/intramolecular interactions, compatibility, and microstructure of bio-based nanostructured composites.

EXPERIMENT

In this work, the impact of pulsed electric fields at a specific energy of 60-700 kJ/kg (electric field strength = 1.6 kV/cm) on self-assembly of zein-chitosan-poly(vinyl alcohol)-polyethylene glycol composite dispersion was investigated at pH 4.0, 5.7, and 6.8.

FINDINGS

Superior complex coacervated matrices were assembled at pH 4.0 and 5.7 before and after pulsed electric fields treatment at a specific energy of 390-410 kJ/kg. The compact and homogenous behaviour was attributable to pulsed electric fields-induced alteration of functional group interactions in a pH-dependent manner. Irrespective of the pH, very high electric field intensity caused excessive system perturbation leading to severe fragmentation and poor development of coacervates. The crucial insights from this study reveal that the self-assembly behaviour and integration of biopolymer-based systems possessing different local charges can be enhanced by optimising pulsed electric fields processing parameters and the properties of the colloidal systems such as the pH.

Co-encapsulation of probiotics with prebiotics and their application in functional/synbiotic dairy products

Oral administration of live probiotics along with prebiotics has been suggested with numerous beneficial effects for several conditions including certain infectious disorders, diarrheal illnesses, some inflammatory bowel diseases, and most recently, irritable bowel syndrome. Though, delivery of such viable bacteria to the host intestine is a major challenge, due to the poor survival of the ingested probiotic bacteria during the gastric transit, especially within the stomach where the pH is highly acidic. Although microencapsulation has been known as a promising approach for improving the viability of probiotics in the human digestive tract, the success rate is not satisfactory. For this reason, co-encapsulation of probiotics with probiotics has been practised as a novel alternative approach for further improvement of the oral delivery of viable probiotics toward their targeted release in the host intestine. This paper discusses the co-encapsulation technologies used for delivery of probiotics toward better stability and viability, as well the incorporation of co-encapsulated probiotics and prebiotics in functional/synbiotic dairy foods. The common encapsulation technologies (and the materials) used for this purpose, the stability and survival of co-encapsulated probiotics in the food, and the release behavior of the co-encapsulated probiotics in the gastrointestinal tract have also been explained. Most studies reported a significant improvement particularly in the viability of bacteria associated with the presence of prebiotics. Nevertheless, the previous research has mostly been carried out in the simulated digestion, meaning that future systematic research is to be carried out to investigate the efficacy of the co-encapsulation on the survival of the bacteria in the gut in vivo.

Fabrication and characterization of double (W1/O/W2) emulsions loaded with bioactive peptide/polysaccharide complexes in the internal water (W1) phase for controllable release of bioactive peptide

The objective of this study was to develop food-grade double emulsions containing bioactive peptide (BP)/polysaccharide (P) complexes and to investigate their thermal stability (e.g., BP release) at different temperatures. The BP/P complexes were formed via electrostatic interactions, and successfully encapsulated into the internal water phase of double emulsions with different oil phases. All emulsions clearly showed temperature dependence during storage. BP/P complex-loaded double emulsions showed higher thermal stability and lower release of encapsulated BP (45 °C: < 1%, 65 °C: < 30%) over time, which effectively prevented BP release within the emulsion system. For the effect of the oil phase, the BP released from double emulsions was in the order of MCT > coconut > canola oil. Thus, we concluded that BP release can be controlled in double emulsions by differently charged polysaccharides and oil types and that BP/P-loaded double emulsions can be utilized as functional ingredients for developing heat-sensitive food products.

Use of gelatin and gum arabic for microencapsulation of probiotic cells from Lactobacillus plantarum by a dual process combining double emulsification followed by complex coacervation

The objectives of this study were i) to microencapsulate probiotic cells of Lactobacillus plantarum through a dual process consisting of emulsification followed by complex coacervation using gelatin and gum arabic, ii) to characterize the lyophilized microcapsules, iii) to evaluate their behavior in simulated in vitro gastrointestinal conditions and iv) to evaluate the survival of microencapsulated probiotic cells during 45 days of storage at 8 °C, 25 °C and -18 °C. The optimized conditions for complex coacervation consisted of a 50:50 biopolymer ratio and pH = 4.0. Emulsification was followed by complex coacervation using gelatin and gum arabic. The microcapsules presented dispersibility of 0.183 ± 0.17 g·mL^-1, moisture content of 4.5%, water activity of 0.34 ± 0.03 and hygroscopicity of 9.20 ± 0.43 g of absorbed water per 100 g. Their size ranged from 66.07 ± 3.04 μm to 105.66 ± 3.24 μm. Viability of the encapsulated L. plantarum cells was 8.6 log CFU·g^-1 and the encapsulation efficiency was 97.78%. After in vitro simulation of gastrointestinal conditions, viability of the encapsulated cells was 80.4% whereas it was only 25.0% for the free cells at 37 °C. Probiotic cell viability was maintained during storage at 8 °C and - 18 °C for 45 days.

Preparation of microcapsule antioxidative wall materials of pine nut oil by the Maillard reaction

BACKGROUND

Maillard reaction products contribute to the amelioration of the biological functions or physical properties of foods and can be used to make dependable antioxidant wall materials for microcapsules of pine nut oil. The present study aimed to analyze the effects of temperature on the Maillard reaction of dry heat processes using gelatin/gum arabic (GE/GA) or gelatin/gum arabic/maltodextrin (GE/GA/MD) models and the products of the Maillard reaction as encapsulants to protect pine nut oil, as well as to evaluate the characteristics of the microcapsules.

RESULTS

The grafting degree of the product increased with the temperature increments during the Maillard reaction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the polysaccharide covalently linked to the protein. The antioxidant capability of the Maillard products at 80 °C was the highest. The 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, lipid peroxidation-inhibiting activity and reducing power of the GE/GA/MD model were higher than those of the GE/GA model. With in vitro digestion of Maillard products, GE/GA/MD pine nut oil microcapsules exhibited greater oil release in artificial gastric and enteric juices. Microencapsulated pine nut oil had more stable oxygen, which protected the oil, compared to unencapsulated pine nut oil.

CONCLUSION

Temperature affects the degree of the Maillard reaction on GE/GA and GE/GA/MD models. © 2018 Society of Chemical Industry.

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.

Complex Coacervation of Milk Proteins with Sodium Alginate

Beta-lactoglobulin (BLG) and bovine serum albumin (BSA) coacervate formation with sodium alginate (ALG) was investigated by turbidimetric analysis, zeta potential, particle size, viscosity, transmission electron microscopy (TEM) and isothermal titration calorimetric (ITC) measurements as a function of pH (1.0-7.0) and protein/alginate mixing ratio (1:1, 1.5:1, 2:1, 1:0, and 0:1 wt.). Critical pH values of phase transitions for BSA-ALG complexes (pH_C, pH_φ1, and pHφ_φ2) representing the formation of soluble and insoluble complexes of a protein-ALG mixture (2:1) at pH 4.8, 4.2, and 1.8, respectively. In the case of BLG-ALG, critical pH values (pH_C, pH_φ1, and pH_φ2) were found to be 4.8, 4.2, and 1.6, respectively. The pH_opt values, expressed by the highest optical density, were pH 2.8 for BSA-ALG and 2.4 for BLG-ALG. TEM and zeta-potential results showed that maximum coacervate formation occurred at pH 4.2 for both protein-polysaccharide solutions. The interaction between BLG-ALG and BSA-ALG was spontaneously exothermic at pH 4.2 according to ITC measurements. The findings of this study provide insights to a thorough understanding about the nature of interactions between milk proteins and ALG and formulate new applications for food, pharmaceutical, nutraceutical, and cosmetics applications.

Effect of the Helix-Coil Transition in Bovine Skin Gelatin on Its Associative Phase Separation with Lysozyme

It is known that the formation of electrostatic polyelectrolyte complexes can induce conformational changes in the interacting macromolecules. However, the opposite effect, namely, that of the helix-coil transition of one of the interacting polyelectrolytes on its associative phase separation with another polyelectrolyte and the possible phase transitions in such systems, has not been determined. Atomic force and confocal laser scanning microscopy, phase analysis, dynamic and electrophoretic light scattering, turbidimetry, absorption, and fluorescence measurements as well as differential scanning calorimetry and rheology were used to study the effect of the helix-coil transition in bovine skin gelatin (Gel) on its associative phase separation with hen egg white lysozyme (Lys) at different temperatures (18-40 °C) and various Lys/Gel weight ratios (0.01-100) at low ionic strength (0.01) and pH 7.0. The effects of the main variables on the phase state, the phase diagram, and the main complexation and binding parameters as well as the temperature and enthalpy of the helix-coil transition of Gel within the complexes were investigated. Associative phase separation is observed only for the system with Gel in the helix state. Effective charge and structure and the solution and rheological behavior of the formed complexes proved to be dependent on the [An^-]/[Cat⁺] charge ratio. The localization of Lys within the complex particles has irregular character without the formation of a single center of binding. The binding of Lys with Gel does not lead to the disruption of its tertiary structure or to an appreciable change in the thermodynamic parameters of the thermal transitions of Lys. Gel in the coil state interacts only weakly with Lys, forming water-soluble complex associates. It is suggested that the Voorn-Overbeek model could potentially describe the stronger binding and phase separation in the case of Gel in the helix state.

Modification of pea protein isolate for ultrasonic encapsulation of functional liquids

This study reports on the ultrasonic processing of pea protein isolate (PPI) in phosphate-buffered saline (PBS, pH 7.4) and Tris/HCl (pH 8) buffer systems in order to modify its properties for use in the encapsulation of functional liquids.

Complex coacervation with whey protein isolate and gum arabic for the microencapsulation of omega-3 rich tuna oil

Tuna oil rich in omega-3 fatty acids was microencapsulated in whey protein isolate (WPI)-gum arabic (GA) complex coacervates, and subsequently dried using spray and freeze drying to produce solid microcapsules. The oxidative stability, oil microencapsulation efficiency, surface oil and morphology of these solid microcapsules were determined. The complex coacervation process between WPI and GA was optimised in terms of pH, and WPI-to-GA ratio, using zeta potential, turbidity, and morphology of the microcapsules. The optimum pH and WPI-to-GA ratio for complex coacervation was found to be 3.75 and 3 : 1, respectively. The spray dried solid microcapsules had better stability against oxidation, higher oil microencapsulation efficiency and lower surface oil content compared to the freeze dried microcapsules. The surface of the spray dried microcapsules did not show microscopic pores while the surface of the freeze dried microcapsules was more porous. This study suggests that solid microcapsules of omega-3 rich oils can be produced using WPI-GA complex coacervates followed by spray drying and these microcapsules can be quite stable against oxidation. These microcapsules can have many potential applications in the functional food and nutraceuticals industry.