Formation, stability and the application of Pickering emulsions stabilized with OSA starch/chitosan complexes

Preparation of temperature-responsive pickering emulsions for encapsulating compound essential oils and their application in fresh noodle preservation

In the present study, corn starch was modified to create temperature-responsive particles, which were employed as an emulsifier to formulate Pickering emulsions (PE) for the encapsulation of compound essential oils (CEO). The temperature responsiveness of CEOPE endows PE with the characteristics of faster release rate at lower temperature and more stability at room temperature, aligning with the typical low-temperature storage conditions of fresh noodles. The characteristics of CEOPE with different oil-water ratios were analyzed by morphology, particle size, PDI, zeta-potential, FTIR and rheological measurements. The CEOPE exhibited antibacterial activity against E. coli and S. aureus, making it an ideal candidate for non-contact antibacterial packaging. The antibacterial effect was further confirmed in the storage experiment of fresh noodles. The results have significant implications for the development of a temperature-responsive, bacteriostatic packaging material derived from natural components, offering a novel approach to the preservation of fresh noodles.

Chitosan-based Pickering double emulsion microcapsules improve the UV stability and the persistence of Bacillus thuringiensis on mosquito control

Bacillus thuringiensis (Bt) is affected by ultraviolet radiation and bacterial sedimentation in pest control applications, leading to low pesticide utilization and a short duration of control. To improve Bt stability in these applications and prolong the duration of biological control, Bt LLP29 was first encapsulated using double emulsion technology, resulting in the formation of W1/O/W2 double emulsion microcapsules with sodium lignosulfonate and chitosan as wall materials. The morphological structure and functionality of microcapsules were then systematically investigated. Notably, the survival rates of Bt bacteria and spores in the microcapsules were maintained at 22.98 % and 8.18 % after 96 h of UV irradiation, and the retention rate of insecticidal protein was increased by 41.42 % after 72 h, with high mosquito-killing activity maintained. Furthermore, the Bt microcapsules exhibited excellent suspension properties and sustained release capabilities, which enhanced the retention of Bt active ingredients in the environment of young mosquitoes and extended the duration of pest control. These studies pioneered the application of double emulsion technology and microcapsules to the encapsulation of Bt based on the functional properties of chitosan. This will pave the way for the development of multifunctional Bt preparations in agricultural applications and pest control.

Understanding the role of Radix Paeoniae Alba polysaccharide for corn starch gel amelioration: Physicochemical, structural, and digestive properties

To ameliorate the limitations of corn starch (CS) processing, Radix Paeoniae Alba polysaccharide (RPAP) was used to modulate the physicochemical and digestive properties of CS. The main purpose of this paper is to investigate the effects of RPAP on the pasting, rheological, thermal, structural, and digestive properties of CS. The results show that the addition of RPAP could increase the peak viscosity and final viscosity of CS gel, and RPAP could increase the apparent viscosity, storage modulus, loss modulus, hardness, and strength of CS gel, implying that RPAP can effectively improve the pasting and viscoelasticity properties of CS. Moreover, RPAP could be bound to CS through non-covalent interaction, and RPAP could improve the relative crystallinity and thermal stability, whereas decreased the spin relaxation time (T2) of CS from 312.16 to 203.25 ms. The microstructure of CS-RPAP gels showed a honeycomb-like porous structure, and RPAP could increase the pore size and thickness of CS-RPAP gels. Furthermore, RPAP could inhibit the digestibility of CS, while increased the resistant starch (RS) content. The findings can provide important references for expanding the application of starch-based products in various fields including food industry, pharmaceuticals, textiles, papermaking, and biodegradable materials.

Effects of molecular weight of chitosan on its binding ability with OSA starch and oil-water interface behavior of complex-stabilized emulsion

This work examined the effects of molecular weight (2-15 kDa) and concentration (10-30 mg/mL) of chitosan (CTS) on the binding capacity and interface behavior between octenyl succinic acid sodium starch (OSS) and CTS, as well as their effects on the storage stability of emulsions. The results of the isothermal calorimetry titration demonstrated that OSS and CTS were complexed by electrostatic interaction and spontaneous hydrogen bonding driven by enthalpy (ΔH from -3931 to -7983 cal/mol, ΔS from -38.5 to -49.2 cal/mol/deg., ΔG from -6436.6 to -7542.0 cal/mol), and the affinity and binding capacity (N = 2.83-22.90 sites) were reinforced with CTS molecular weight. The interfacial adsorption kinetics revealed that the OSS/CTS complexes with high-molecular-weight CTS exhibited a markedly accelerated rate of interfacial diffusion and recombination, and rapidly reduced interfacial tension. CTS incorporation enhanced mass (1980.32-3522.56 ng/cm2), thickness (35.12-51.29 nm), viscosity (52.81-67.06 kPa), and elasticity (1.70-3.49 kPa) of interfacial film through the dissipative quartz crystal microbalance. OSS/CTS complexes displayed superior emulsification properties and adjustable interfacial viscoelastic ratio in response to frequency interference. Emulsions stabilized by the OSS/CTS complexes with high molecular weight and concentration of CTS exhibited more uniform spherical structures and superior storage stability. This work will facilitate the broader utilization of OSS and CTS in the emulsion delivery system.

Chitosan decoration enhanced the thermal and ultraviolet resistance of vitamin A-vitamin D coencapsulated in OSA starch-stabilized emulsion by regulating viscoelasticity, interfacial thickness and structure

In this study, octenyl succinic acid sodium starch (OSAS) decorated with chitosan (CS) of different molecular weights (50-150 kDa) and concentrations (10-30 mg/mL) was used to stabilize an emulsion coencapsulating with vitamin A (VA) and vitamin D (VD). The effect of CS decoration on the thermal and UV stability of the emulsion, as well as the underlying mechanism, was elucidated. The incorporation of CS increased the retention rates of VA and VD by 11.36-25.52 % and 3.65-20.54 %, respectively, when exposed to 100 °C for 30 min, and by 13.35-33.05 % and 15.97-37.49 %, respectively, under ultraviolet (UV) exposure for 12 h, respectively. The OSAS/CS complexes were absorbed at the oil-water interface through electrostatic interactions and hydrogen bonding, forming thick interfacial film barriers, and regulating emulsion viscoelasticity to achieve protection against thermal and UV damage. CS decoration increased the thickness, relative crystallinity, and thermal degradation resistance of the interfacial films to mitigate thermal interference with the emulsion. The OSAS/CS complex barriers shielded UV by forming longer molecular chains or ring structures at the interface, enhancing amide functionality, and promoting intermolecular hydrogen bonding. This research could provide a reference for designing practical delivery systems for heat-sensitive and UV-sensitive nutrients like VA and VD.

Interfacial engineering of Pickering emulsions stabilized by pea protein-alginate microgels for encapsulation of hydrophobic bioactives

This study aims to investigate the effects of interfacial layer composition and structure on the formation, physicochemical properties and stability of Pickering emulsions. Interfacial layers were formed using pea protein isolate (PPI), PPI microgel particles (PPIMP), a mixture of PPIMP and sodium alginate (PPIMP-SA), or PPIMP-SA conjugate. The encapsulation and protective effects on different hydrophobic bioactives were then evaluated within these Pickering emulsions. The results demonstrated that the PPIMP-SA conjugate formed thick and robust interfacial layers around the oil droplet surfaces, which increased the resistance of the emulsion to coalescence, creaming, and environmental stresses, including heating, light exposure, and freezing-thawing cycle. Additionally, the emulsion stabilized by the PPIMP-SA conjugate significantly improved the photothermal stability of hydrophobic bioactives, retaining a higher percentage of their original content compared to those in non-encapsulated forms. Overall, the novel protein microgels and the conjugate developed in this study have great potential for improving the physicochemical stability of emulsified foods.

Enhancement of Pickering effect of ovalbumin with bacterial cellulose nanofibers prepared by electron beam irradiation and encapsulation of curcumin

In this study, the enhancement of Pickering effect of ovalbumin (OVA) with bacterial cellulose nanofibers (BCNFs) prepared by electron beam irradiation was investigated and the environmental stability of oil-in-water Pickering emulsions stabilized by OVA/BCNFs complexes was explored by varying ratios of OVA/BCNFS (1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1) and oil phase concentrations (10 %, 20 %, 30 %, 40 %, 50 %, 60 %). Droplet sizes of Pickering emulsions were decreased with the increase of the proportion of BCNFs, while the viscosity and storage modulus (G') of Pickering emulsions were increased. The gel strength of Pickering emulsions was positively correlated with the oil phase content. Pickering emulsions stabilized by OVA/BCNFs complexes were endowed excellent environmental stability under varying pH, ionic strength, and thermal conditions. Moreover, after encapsulating curcumin in Pickering emulsions, the retention rates of curcumin were improved significantly during room temperature, UV light, and thermal treatment. The present study would contribute to the advancement of novel protein/polysaccharide stabilizers and offer novel insight for investigating the stability of Pickering emulsions and delivering lipophilic bioactive compounds.

Using natural starch granules to disperse solid beeswax into micron-sized droplets in emulsion

Use of beeswax together with starch to manufacture emulsion for fruit preservation has attracted wide attention in food packaging. In this paper, esterified starch (M-PS) granules prepared from natural potato starch were used to replace nanocrystals to prepare beeswax emulsion. The swelling property of M-PS granules was used to solve the problem of uneven dispersion of beeswax. Atomic force microscope (AFM) images showed that the network gel structure formed by M-PS granules limited the movement of beeswax droplets, and the droplet size was <1.0 μm. When the beeswax emulsion was added to the starch paste, the resulting starch-beeswax composite emulsion had a stable gel structure. Bananas were coated with the composite emulsion. After 7 days of storage, compared with the test data of bare bananas, the weight loss rate decreased by 42 %, the titratable acidity increased by 21 %, and the vitamin C was higher by 20 % of coated bananas. The formed coating effectively inhibited the decline of banana quality.

Plant gums in Pickering emulsions: A review of sources, properties, applications, and future perspectives

Recently, there has been an increasing research interest in the development of Pickering emulsions stabilized with naturally derived biopolymeric particles. In this regard, plant gums, obtained as plant exudates or from plant seeds, are considered promising candidates for the development of non-toxic, biocompatible, biodegradable and eco-friendly Pickering stabilizers. The main objective of this review article is to provide a detailed overview and assess the latest advances in the formulation of Pickering emulsions stabilized with plant gum-based particles. The plant gum sources, types and properties are outlined. Besides, the current methodologies used in the production of plant gum particles formed solely of plant gums, or through interactions of plant gums with proteins or other polysaccharides are highlighted and discussed. Furthermore, the work compiles and assesses the innovative applications of plant gum-based Pickering emulsions in areas such as encapsulation and delivery of drugs and active agents, along with the utilization of these Pickering emulsions in the development of active packaging films, plant-based products and low-fat food formulations. The last part of the review presents potential future research trends that are expected to motivate and direct research to areas related to other novel food applications, as well as tissue engineering and environmental applications.

Effects of different oil fractions and tannic acid concentrations on konjac glucomannan-stabilized emulsions

Polysaccharide-stabilized emulsions have received extensive attention, but emulsifying activity of polysaccharides is poor. In this study, konjac glucomannan (KGM) and tannic acid (TA) complex (KGM-TA) was prepared via non-covalent binding to increase the polysaccharide interfacial stability. The emulsifying stabilities of KGM-TA complex-stabilized emulsions were analyzed under different TA concentrations and oil fractions. The results indicated that hydrogen bonds and hydrophobic bonds were the main binding forces for KGM-TA complex, which were closely related to TA concentrations. The interfacial tension of KGM-TA complex decreased from 20.0 mN/m to 13.4 mN/m with TA concentration increasing from 0 % to 0.3 %, indicating that TA improved the interfacial activity of KGM. Meanwhile, the contact angle of KGM-TA complex was closer to 90° with the increasing TA concentrations. The emulsifying stability of KGM-TA complex-stabilized emulsions increased in an oil mass fraction-dependent manner, reaching the maximum at 75 % oil mass fraction. Moreover, the droplet sizes of KGM-TA complex-stabilized high-internal-phase emulsions (HIPEs) decreased from 82.7 μm to 44.7 μm with TA concentration increasing from 0 to 0.3 %. Therefore, high TA concentrations were conducive to the improvement of the emulsifying stability of KGM-TA complex-stabilized HIPEs. High oil mass fraction promoted the interfacial contact of adjacent droplets, thus enhancing the non-covalent binding of KGM molecules at the interfaces with TA as bridges. Additionally, the high TA concentrations increased the gel network density in the aqueous phase, thus enhancing the emulsifying stability of emulsions. Our findings reveal the mechanisms by which polysaccharide-polyphenol complex stabilized HIPEs. Therefore, this study provides theoretical basis and references for the developments of polysaccharide emulsifier with high emulsifying capability and high-stability emulsions.

Starch-based particles as stabilizers for Pickering emulsions: modification, characteristics, stabilization, and applications

The potential utilization of starch as a particle-based emulsifier in the preparation of Pickering emulsions is gaining interest within the food industry. Starch is an affordable and abundant functional ingredient, which makes it an excellent candidate for the stabilization of Pickering emulsions. This review article focuses on the formation, stabilization, and properties of Pickering emulsions formulated using starch-based particles and their derivatives. First, methods of isolating and modifying starch-based particles are highlighted. The key parameters governing the properties of starch-stabilized Pickering emulsions are then discussed, including the concentration, size, morphology, charge, and wettability of the starch-based particles, as well as the type and size of the oil droplets. The physicochemical mechanisms underlying the ability of starch-based particles to form and stabilize Pickering emulsions are also discussed. Starch-based Pickering emulsions tend to be more resistant to coalescence than conventional emulsions, which is useful for some food applications. Potential applications of starch-stabilized Pickering emulsions are reviewed, as well as recent studies on their gastrointestinal fate. The information provided may stimulate the utilization of starch-based Pickering emulsions in food and other industries.

Analysis of instability of starch-based Pickering emulsion under acidic condition of pH < 4 and improvement of emulsion stability

Starch-based Pickering emulsions exhibit high interfacial stability in a certain range of mild pH environments. On the contrary, many studies have reported that when the pH value is <4, it often leads to different degrees of emulsion instability. In this paper, the microscopic state of starch granules in the emulsion and its effect on the stability of the emulsion were observed and analyzed by atomic force microscope (AFM) in tapping mode. At the same time, Pickering emulsions in acidic environment were prepared by using the gel properties of methyl cellulose (MC) in synergy with esterified high amylose maize starch (M-HAMS) granules. The results show that in the emulsion with pH 3, the excessive H + ion inhibits the swelling of M-HAMS granules and prevents it from forming a stable gel structure, which is the main cause of emulsion instability. The polarity of MC with water contact angle (WCA) of 81.8° is similar to that of M-HAMS granules with WCA of 80.1°, and a uniform and ordered micro-nanostructure is formed in the aqueous phase. The prepared acidic (pH 3-4) emulsion has good stability during the observation period of 30 days.

Influence of varying oil phase volume fractions on the characteristics of flaxseed-derived diglyceride-based Pickering emulsions stabilized by modified soy protein isolate

This research aimed to create Pickering emulsions using modified soy protein isolate (SPI) as a stabilizer and flaxseed-derived diglyceride (DAG) as an oil phase. The SPI was modified through a process involving both heating and ultrasound treatment. The result indicated that the droplet size of emulsions increased with the increase in oil content (p < 0.05). For instance, the largest droplet size (23 µm) was observed at an oil-to-SPI dispersion ratio of 4:1 ratio (φ = 80), whereas the smallest droplet size (6.39 µm) was noticed at the 1:4 ratio. During the 7-day storage period, the emulsions with a 4:1 ratio (φ = 80) showed the lowest droplet size increase (from 23 µm to 25.58 µm). In contrast, the emulsions with a 1:1 ratio displayed the highest increase (from 19.39 µm to 74.29 µm). Creaming index results revealed that emulsions with a 4:1 ratio (φ = 80) showed no signs of creaming and phase separation than all other treatments (p < 0.05). Backscattering fluctuations (ΔBS) and turbiscan stability index (TSI) showed that emulsions with 4:1, 2:1, and 1:1 oil-to-SPI dispersion ratios had consistent ΔBS curves with higher and TSI curves with lower values. Optical microscopy, confocal laser scanning, and cryo-scanning electron microscopy revealed that emulsions with oil-to-SPI dispersion ratios of 4:1 and 2:1 had well-organized structures with no visible coalescence. Macromorphological and microrheological investigations demonstrated that emulsions with 80% oil content had the highest viscosity, both moduli, elasticity index, macroscopic viscosity index, and the lowest fluidity index and solid-liquid balance values. Moreover, these emulsions were more resistant to centrifugation and storage environments. In conclusion, the study determined that flaxseed-derived DAG-based high internal phase Pickering emulsions (φ = 80) had superior stability, improved viscoelasticity, and better rheological properties.

Noncovalent interactions between biomolecules facilitated their application in food emulsions' construction: A review

The use of biomolecules, such as proteins, polysaccharides, saponins, and phospholipids, instead of synthetic emulsifiers in food emulsion creation has generated significant interest among food scientists due to their advantages of being nontoxic, harmless, edible, and biocompatible. However, using a single biomolecule may not always meet practical needs for food emulsion applications. Therefore, biomolecules often require modification to achieve ideal interfacial properties. Among them, noncovalent interactions between biomolecules represent a promising physical modification method to modulate their interfacial properties without causing the health risks associated with forming new chemical bonds. Electrostatic interactions, hydrophobic interactions, and hydrogen bonding are examples of noncovalent interactions that facilitate biomolecules' effective applications in food emulsions. These interactions positively impact the physical stability, oxidative stability, digestibility, delivery characteristics, response sensitivity, and printability of biomolecule-based food emulsions. Nevertheless, using noncovalent interactions between biomolecules to facilitate their application in food emulsions still has limitations that need further improvement. This review introduced common biomolecule emulsifiers, the promotion effect of noncovalent interactions between biomolecules on the construction of emulsions with different biomolecules, their positive impact on the performance of emulsions, as well as their limitations and prospects in the construction of biomolecule-based emulsions. In conclusion, the future design and development of food emulsions will increasingly rely on noncovalent interactions between biomolecules. However, further improvements are necessary to fully exploit these interactions for constructing biomolecule-based emulsions.

Preparation of lauric acid esterified starch by ethanol solvothermal process and its Pickering emulsion

In this paper, the esterification modification of different kinds of starches such as waxy maize, normal maize, high-amylose maize, cassava and potato in high temperature closed system were studied by solvothermal method. The oil-in-water Pickering emulsion were prepared with esterified starches as granule stabilizer. The microscopic state of granules in the emulsion and the physical and oxidation stability of emulsion were studied. The results show that starches are not gelatinized and can be esterified at a temperature (100 °C) much higher than that of gelatinization, and the granule morphology is almost unchanged. DS (degree of substitution) values of esterified starches range from 0.0333 to 0.0512. Pickering emulsion with 50 vol% oil volume fraction prepared with 3.0 wt% granule concentration did not show any instability such as oil-water separation after storage at room temperature for 30 days. Atomic force microscope (AFM) analysis showed that all esterified starch granules had the characteristics of granular cold-water swelling starch (GCWSS). The granules completely swelled into a dense molecular chain in the emulsion, and this three-dimensional network structure improved the stability of emulsion. Therefore, the preparation of esterified starch granules by ethanol solvothermal method is a simple and effective method.

Tuning interfacial microstructure of alginate-based amphiphile by dynamic bonding for stabilizing Pickering emulsion

Polysaccharide-based soft colloidal particles mediated by the dynamic bonding-engineered interfacial self-assembly can regulate the properties of oil-water interfacial films, availing the stability of emulsions under a wide pH range. The amphiphilic phenylboronic alginate soft colloidal particles (Alg-PBA) were designed to stabilize pH-responsive Pickering emulsions (PEs). Combining stability analysis with quartz crystal microbalance and dissipation monitoring (QCM-D), the microstructure and viscoelasticity of Alg-PBA at the oil-water interface were determined. The results showed that PEs stabilized by Alg-PBA due to a thicker and stronger viscoelastic interface film induced by BO bonds and hydrogen bonds. The structure-function relationship of the Alg-PBA emulsifier driven by dynamic bonds was further elaborated at multiple scales by laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Meanwhile, the microstructure of aerogels templated by emulsion could be tuned by adjusting dynamic bonds, which provides a new idea for polysaccharide soft material engineering.

Stability, oxidizability, and topical delivery of resveratrol encapsulated in octenyl succinic anhydride starch/chitosan complex-stabilized high internal phase Pickering emulsions

High internal phase Pickering emulsions (HIPPEs) stabilized with octenyl succinic anhydride starch/chitosan complexes were examined as a topical delivery vehicle for resveratrol. All resveratrol-loaded HIPPEs showed stable gel-like network structures, with the droplet size and microrheological properties largely dependent on the complex concentrations. HIPPEs exhibited strong stability when subjected to light, high temperature, UV radiation and freeze-thaw treatment, and resveratrol retention was greatly improved with the increasing addition of complexes and resveratrol. High amounts of resveratrol facilitated the antioxidant activity of HIPPEs, whereas sustained release of resveratrol was mainly related to the existence of complex interfacial layers. Moreover, HIPPEs overcome the stratum corneum barrier, with an approximately 3-5-fold increase in resveratrol deposition in deep skin compared to bulk oil. In conclusion, the emulsion composition (especially at the particle level) was vital for the effectiveness of HIPPEs as a carrier, which may provide new opportunities to design topical delivery systems.

Biopolymer-based pickering high internal phase emulsions: Intrinsic composition of matrix components, fundamental characteristics and perspective

Pickering HIPEs have received tremendous attention in recent years due to their superior stability and unique solid-like and rheological properties. Biopolymer-based colloidal particles derived from proteins, polysaccharides and polyphenols have been demonstrated to be safety stabilizers for the construction of Pickering HIPEs, which can meet the demands of consumers for "all-natural" products and provide "clean-label" foods. Furthermore, the functionality of these biopolymers can be further extended by forming composite, conjugated and multi-component colloidal particles, which can be used to modulate the properties of the interfacial layer, thereby adjusting the performance and stability of Pickering HIPEs. In this review, the factors affecting the interfacial behavior and adsorption characteristics of colloidal particles are discussed. The intrinsic composition of matrix components and fundamental characteristics of Pickering HIPEs are emphatically summarized, and the emerging applications of Pickering HIPEs in the food industry are reviewed. Inspired by these findings, future perspectives concerning this field are also put forward, including (1) the exploration of the interactions between biopolymers used to produce Pickering HIPEs and target food ingredients, and the influence of the added biopolymers on the flavor and mouthfeel of the products, (2) the investigation of the digestion properties of Pickering HIPEs under oral administration, and (3) the fabrication of stimulus-responsive or transparent Pickering HIPEs. This review will give a reference for exploring more natural biopolymers for Pickering HIPEs application development.