Development of Pickering Emulsions Stabilized by Gliadin/Proanthocyanidins Hybrid Particles (GPHPs) and the Fate of Lipid Oxidation and Digestion

Food-grade rapeseed cake particles: Production, physicochemical characteristics, and emulsifying properties

Rapeseed cake is rich in dietary fibers and proteins, but is predominantly used as fertilizer, with limited utilization in other applications. This study aimed to develop a food-grade holo-cellulose rapeseed cake fibrous particles stabilizer using hush pre-treatment (sequential alkali-acid, and heat), followed by ultrasonic cavitation (USC) or high-pressure microjet (HPM) processing. The pretreatment improved particle suspension stability (ζ-potential: -1.9 ± 1.5 mV to -42.5 ± 2.0 mV) and hydrophobicity (contact angle: 59.6 ± 1.9° to 81.3 ± 2.2°), endowing the particles with excellent emulsifying properties. Subsequent USC and HPM treatments decreased particle size and improved suspension stability further. The treated particles showed an octopus-like entangled enabling stable anchoring at the interface of oil and water. These particles formed a rigid network, contributing to the formation of robust emulsion gels. This study provides a feasible strategy for the advanced processing of rapeseed cake, expanding its potential applications in gel-based food industry and, promoting its high-value applications.

Influence pathways of covalent and non-covalent interactions on the stability of deamidated gliadin-tannic acid-based Pickering emulsions

This study aimed to elucidate the pathways through which covalent and non-covalent interactions between deamidated gliadin (DG) and tannic acid (TA) on influence the stability of Pickering emulsions. The interactions induced protein unfolding, as evidenced by increased ultraviolet absorption and a red shift in fluorescence emission. DG-TA composite nanoparticles effectively stabilized high internal phase emulsions, whereas DG nanoparticles alone did not. Covalent DG-TA nanoparticle stabilized Pickering emulsions (C-DGTAE) retained a consistent mean droplet size after 30 d of storage. Lipid hydroperoxide and malondialdehyde levels in C-DGTAE and N-DGTAE were reduced by 59.1 %-69.5 % and 38.9 %-44.4 %, respectively. Furthermore, the retention of β-carotene in the emulsions was significantly enhanced. All emulsions exhibited elastic behavior, characterized by higher G' than G″. Notably, N-DGTAE demonstrated the highest apparent viscosity, G' and G″, attributed to the connected nanoparticles around the droplets. Confocal laser scanning microscopy revealed that C-DGTAE droplets possessed the thickest layer, corroborated by the highest interfacial nanoparticle content of 76 % and an interfacial thickness of 441 nm. These findings suggest that covalent interactions enhance the interfacial nanoparticle layer, while non-covalent interactions promote nanoparticle networking, providing valuable insights for optimizing the stability of Pickering emulsions.

Insights into the oil-water interfacial adsorption properties of whey protein-γ-oryzanol Pickering emulsion gel during in vitro simulated digestion

This work elucidated the digestion behavior of low-oil phase Pickering emulsion gel (LOPPEG) stabilized by whey protein isolate (WPI) -γ-Oryzanol (γO) aggregated particles and interfacial adsorption properties of its simulated digestion products. Initially, following simulated digestion, WPI-γO LOPPEG exhibited lower free fatty acid release and protein digestibility compared to WPI LOPPEG. WPI-γO LOPPEG maintained lower interfacial tension and higher interfacial thickness than WPI LOPPEG. The quartz crystal microbalance results further demonstrated that the viscoelasticity and oil-water interfacial adsorption quality of WPI-γO LOPPEG were higher than those of WPI LOPPEG. Ultimately, WPI-γO/pH 7.5 LOPPEG showed the best interfacial adsorption characteristics and anti-digestive properties. This work could provide the theoretical guidance for the development of the slow-digestive foods.

Recent advances in the plant protein-polyphenol interactions for the stabilization of emulsions

Proteins from plant sources including legumes, cereals and oilseeds are gaining attention due to their suitability for sustainable production, functionality, and positive consumer perception. On the other hand, polyphenols (PPs) are receiving considerable attention as natural ingredients in the human diet due to their potent antioxidant and anti-inflammatory properties. Recent studies indicate that the emulsifying properties of plant proteins (PLPs) can be improved after modification through covalent and/or non-covalent interactions with PPs due to the changes in the conformation and/or the surface chemistry of the proteins. Complexes formed between PLPs-PPs can serve as innovative ingredients for developing novel food products with modified textural properties. Also, Pickering emulsions, multiple emulsions, multilayer emulsions, nanoemulsions, and high internal phase emulsions can be stabilized by such systems to deliver bioactive compounds. This paper reviews the most recent research on the PLP-PP interactions and their role in the stabilization of various emulsion-based systems. A special emphasis is given to modifying the structure and functionality of PLPs and PPs. The challenges and opportunities of applying PLP-PP interactions in emulsion-based systems are also highlighted.

Improving emulsion stability: The role of flaxseed gum in stabilizing bovine bone protein hydrolysates emulsions

The use of natural proteins as emulsifiers in stable emulsion systems has gained attention due to the increasing demand for healthy food products. However, the limited thermal stability and ionic tolerance of BBPH restrict its application in emulsions. This study explores the effects of FG on enhancing the stability of BBPH-based emulsions. FTIR and SEM confirmed that BBPH and FG form complexes through hydrophobic and electrostatic interactions, with increasing FG concentrations leading to higher turbidity and particle size. At 0.4 % FG, emulsions showed the smallest particle size (9.12 μm) and the highest zeta potential (-28.73 mV), indicating optimal interaction. Raman spectroscopy further supported these findings, showing enhanced oil-complex interactions and favorable rheological properties. The emulsions exhibited excellent stability during storage, with a creaming index of 1.786 % after 7 days. Oxidation tests showed low POV (0.596 mg/L) and TBARS (6.24 mg/L) after 15 days. FG also improved resistance to environmental stress, providing theoretical support for the broader use of BBPH in the food industry and highlighting FG's potential in stabilizing protein-based emulsions.

Fabrication and characterization of potato short amylose, zein, and pectin ternary composite particles stabilized pickering emulsions and their application on nuciferine delivery

Nuciferine exhibits properties such as reducing blood sugar and fat, however, it is hindered by its poor water solubility and low bioavailability. Pickering emulsions can efficiently encapsulate, protect and deliver active ingredients. In recent years, the use of biologically derived natural materials as emulsifiers to construct Pickering emulsions has become a research hotspot. This research utilized an enzymatic hydrolysis technique to produce short amylose. Subsequently, a ternary composite of short amylose (DBS), zein, and pectin (PEC) was formulated to stabilize Pickering emulsion, with the incorporation of nuciferine aiming to enhance the performance of lotus leaves in terms of both stability and bioavailability. The study revealed that varying amounts of DBS addition had a significant impact on the micromorphological structure and functional properties of DBS-Zein-PEC ternary composite particles. Specifically, the addition of 0.4 g of DBS led to a notable reduction in particle size to 735.2 nm and Zeta potential to -29.6 mV, creating a three-dimensional network with a closely packed lamellar structure. Optimal process conditions for preparing Pickering emulsion included a 3-minute homogenization time, rotation speed of 15000 rpm, and 5 % ternary composite particle addition. Under these conditions, O/W Pickering emulsion was successfully prepared, achieving a 90.5 % encapsulation rate for nuciferine. The resulting emulsion exhibited a minimum particle size of 4.09 μm, displayed good storage stability, resistance to salt ions and pH variations, viscous fluid characteristics, tolerance to oral and gastric environments, and slow release of nuciferine in the small intestine, thereby enhancing its bioavailability. These findings offer insights into the loading and delivery of nuciferine and serve as a technical guide for developing highly stable emulsion gel systems.

Pickering emulsions stabilized by prolamin-based proteins as innovative carriers of bioactive compounds

Pickering emulsions (PEs) can be used as efficient carriers for encapsulation and controlled release of different bioactive compounds. Recent research has revealed the potential of prolamins in development of nanoparticle- and emulsion-based carriers which can improve the stability and bioavailability of bioactive compounds. Prolamin-based particles have been effectively used as stabilizers of various PEs including single PEs, high internal phase PEs, multiple PEs, novel triphasic PEs, and PE gels due to their tunable self-assembly behaviors. Prolamin particles can be fabricated via different techniques including anti-solvent precipitation, dissolution followed by pH adjustment, heating, and ion induced aggregation. Particles fabricated from prolamins alone or in combination with other hydrocolloids or polyphenols have also been used for stabilization of different PEs which were shown to be effective carriers for food bioactives, providing improved stability and functionality. This article covers the recent advances in various PEs stabilized by prolamin particles as innovative carriers for bioactive ingredients. Strategies applied for fabrication of prolamin particles and prolamin-based carriers are discussed. Emerging techno-functional applications of prolamin-based PEs and possible challenges are also highlighted.

Preparation and characteristics of soy protein isolate - Sea buckthorn flavone emulsion and their effects of on quality and heterocyclic amines of roasted mutton granules

A soy protein isolate (SPI) - sea buckthorn flavonoid emulsion was developed to study its effects on roasted lamb quality and heterocyclic amine (HAAs) precursors. The emulsion was stable with uniformly dispersed, well-encapsulated droplets averaging 0.1 to 10 μm. CLSM confirmed its good physical stability, small particle size, and uniform dispersion. FTIR the existence of hydrogen bond, hydrophobic interaction and physical adhesion between SPI and sea-buckthorn flavonoids. The emulsion improved lamb pellet texture by reducing chewiness and hardness, increasing adhesion, and decreasing browning. The emulsion-treated roasted mutton showed a 47.95-53.56 % increase in DPPH scavenging activity and MDA content reduction from 60.78 to 17.80 nmol/mg, indicating strong antioxidant activity and lipid oxidation inhibition. For both precursors and HAAs, there was a significant intensity of inhibition, where creatine decreased by about 44.91-68.34 %, glucose by 84.47 %-97.74 %, and the seven HAAs, Norharman, Harman, IQ, MeIQ, MeIQx, AαC, and PhIP, were inhibited by 79.64 %, respectively, 88.76 %, 65.07 %, 87.27 %, 96.16 %, 89.30 % and 49.44 %, respectively. This study aimed to develop a novel soy protein isolate-sea buckthorn flavonoid emulsion and evaluate its potential to improve roasted lamb quality while inhibiting the formation of harmful HAAs.

Fabrication, characterization and application of Pickering emulsion gels stabilized by defatted grape seed powder

The feasibility of defatted grape seed powder (DGSP) stabilizing Pickering emulsion gels as butter substitute was investigated. The Pickering emulsion gel was constructed using DGSP through high-speed homogenization, and the effects of particle concentration (c) and oil-phase (Medium chain triglyceride) volume fraction (φ) on its structure and properties were investigated. Its application as a butter substitute was also evaluated. The results showed that DGSP had various particle shapes, a wide particle size distribution (3-130 μm), and a three-phase contact angle of 128.9 ± 2.3°. The O/W Pickering emulsion gels with φ ≥ 60% could be obtained at c ≥ 2%. The droplet diameter was negatively correlated with c and positively correlated with φ, while the gel strength was positively related to c and φ. The resulting emulsion gel demonstrated solid-like viscoelastic behavior and pseudoplasticity, and had the potential to serve as a butter substitute. The results can promote the application of grape seeds in food.

Characterization of modified starch-based complexes-stabilized linolenic acid emulsions and their enhanced oxidative stability in vitro gastrointestinal digestion

A new approach of fabricating α-linolenic acid emulsions with enhanced oxidative stability in vitro digestion was established, using covalent octenyl succinic anhydride starch (OSAS)-soy protein (SP)-epigallocatechin-3-gallate (EGCG) complexes as emulsifiers. The physicochemical characteristics and surface morphology of emulsions were mainly characterized by rheological measurements, laser scanning microscope (CLSM) and cryo-scanning electron microscopy (Cryo-SEM). Results indicated that emulsions had dense interfacial layers and strong network structures. As a result, the stability and antioxidant ability of emulsions were improved significantly. In addition, the oxidative stability of emulsions in vitro gastrointestinal digestion was explored. Results showed that emulsions could maintain better oxidative stability owing to antioxidant activity of covalent OSAS-SP-EGCG complexes under gastrointestinal conditions. In particular, lipid hydroperoxide and malondialdehyde contents of emulsions prepared by 1:4 complexes were lower than 0.35 mmol/L and 20.5 nmol/mL, respectively, approximately half those of emulsions stabilized by OSAS (0.65 mmol/L and 39.5 nmol/mL). It was indicated that covalent OSAS-SP-EGCG complexes could effectively inhibit α-linolenic acid oxidation in emulsions during vitro gastrointestinal digestion. This work will provide a theoretical basis for the development of α-linolenic acid emulsions, which will help to broaden application of α-linolenic acid in food industry.

The present state and future outlook of pectin-based nanoparticles in the stabilization of Pickering emulsions

The stabilization of Pickering emulsions using micro/nanoparticles has gained significant attention due to their wide range of potential applications in industries such as cosmetics, food, catalysis, tissue engineering, and drug delivery. There is a growing demand for the development of environmentally friendly micro/nanoparticles to create stable Pickering emulsions. Naturally occurring polysaccharides like pectin offer promising options as they can assemble at oil/water interfaces. This polysaccharide is considered a green candidate because of its biodegradability and renewable nature. The physicochemical properties of micro/nanoparticles, influenced by fabrication methods and post-modification techniques, greatly impact the characteristics and applications of the resulting Pickering emulsions. This review focuses on recent advancements in Pickering emulsions stabilized by pectin-based micro/nanoparticles, as well as the application of functional materials in delivery systems, bio-based films and 3D printing using these emulsions as templates. The effects of micro/nanoparticle properties on the characteristics of Pickering emulsions and their applications are discussed. Additionally, the obstacles that currently hinder the practical implementation of pectin-based micro/nanoparticles and Pickering emulsions, along with future prospects for their development, are addressed.

General approaches to biopolymer-based Pickering emulsions

Pickering emulsion is a type of emulsion that uses solid particles or colloidal particles as emulsifiers rather than surfactants to adhere at oil-water interface. Pickering emulsions have gathered significant research attention recently due to their excellent stability and wide range of potential uses compared to traditional emulsions. Major advancements have been made in development of innovative Pickering emulsions using different colloidal particles by various techniques including homogenization, emulsification and ultrasonication. Use of biopolymer particles gives Pickering emulsions a more escalating possibilities. In this review paper, we seek to present a critical overview of development in food-grade particles that have been utilized to create Pickering emulsions with a focus on techniques and application of Pickering emulsions. Particularly, we have evaluated protein, lipid, polysaccharide-based particles and microalgal proteins that have emerged in recent years with respect to their potential to stabilize and add novel functionalities to Pickering emulsions. Some preparation methods of Pickering emulsions in brief, applications of Pickering emulsions are also highlighted. Encapsulation and delivery of bioactive compounds, fat substitutes, film formation and catalysis are potential applications of Pickering emulsions. Pickering double emulsions, nutraceutical and bioactive co-delivery, and preparation of porous materials are among research trends of food-grade Pickering emulsions.

Preparation and Characterization of Fish Oil Pickering Emulsions Stabilized by Resveratrol-Loaded Gliadin/Chitin Nanocrystal Composite Nanoparticles

Unsaturated fatty acids present in fish oil offer various physiological benefits to the human body. However, their susceptibility to oxidation severely limits their potential applications. The purpose of this study was to develop Pickering emulsions stabilized from a composite of resveratrol-loaded gliadin nanoparticles and oxidized chitin nanocrystals (GR/OC) to protect fish oil from oxidation. The effects of the GR/OC composite on the characterizations of fish oil Pickering emulsions were investigated, including the microstructure, physicochemical properties (stability and rheological behavior), and digestion properties in vitro. The results revealed that an increased concentration of the GR/OC composite significantly reduced the droplet size and improved the ambient stability of the emulsions (in terms of pH, ionic strength, temperature, and storage time). Confocal laser scanning microscopy images depicted that the GR/OC nanoparticles were uniformly dispersed at the interface between water and fish oil (W-O interface). This distribution formed a protective envelope around the droplets. Remarkably, the addition of 2% GR/OC nanoparticles stabilized the Pickering emulsions and showed the most positive effect on the antioxidant capacity compared to that of the control group. These stabilized emulsions maintained lower peroxide values and acid values, which were 1.5 times less than those of the blank control during the 14 day accelerated oxidation experiment. Furthermore, the Pickering emulsions stabilized by GR/OC nanoparticles exhibited the ability to protect fish oil from contamination by gastric juices and facilitate the intestinal absorption of omega-3 polyunsaturated fatty acids. The findings suggest that these GR/OC-stabilized Pickering emulsions offer a promising alternative for delivering fish oils in various industries, including the food industry.

Lipid oxidation in emulsions: New insights from the past two decades

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products.

Phycocyanin/tannic acid complex nanoparticles as Pickering stabilizer with synergistic interfacial antioxidant properties

This study reported a type of phycocyanin (PC)-tannic acid (TA) complex nanoparticles (NPs) fabricated by simply mixing PC with TA at appropriate mass ratios. The assembly of PC-TA NPs was driven by secondary forces involving hydrophobic interactions and hydrogen bonding. PC-TA NPs promoted formations of Pickering emulsions with an oil volume fraction (φ) of 0.1-0.8. The interfacial antioxidant ability of PC-TA NPs was evaluated by comparing the contents of hydroperoxides, malonaldehyde, and hexanal due to lipid oxidation. The results showed that PC-TA NPs retarded lipid oxidation more efficiently than did PC, TA, tween 20, or tween 80, which suggested the synergistic antioxidant action of PC and TA. Besides, the PC-TA NPs stabilized high internal phase emulsion facilitated a higher retention of β-carotene under UV irradiation. Altogether, our findings demonstrate that the modification of PC by TA represents a strategy to fabricate PC-TA NPs with enhanced emulsification and antioxidant efficiency.

Lima bean (Phaseolus lunatus Linn.) protein isolate as a promising plant protein mixed with xanthan gum for stabilizing oil-in-water emulsions

BACKGROUND

Lima bean protein isolate (LPI) is an underutilized plant protein. Similar to other plant proteins, it may display poor emulsification properties. In order to improve its emulsifying properties, one effective approach is using protein and polysaccharide mixtures. This work investigated the structural and emulsifying properties of LPI as well as the development of an LPI/xanthan gum (XG)-stabilized oil-in-water emulsion.

RESULTS

The highest protein solubility (84.14%) of LPI was observed and the molecular weights (Mw ) of most LPI subunits were less than 35 kDa. The enhanced emulsifying activity index (15.97 m2  g-1 ) of LPI might be associated with its relatively high protein solubility and more low-Mw subunits (Mw  < 35 kDa). The effects of oil volume fraction (ϕ) on droplet size, microstructure, rheological behavior and stability of emulsions were investigated. As ϕ increased from 0.2 to 0.8, the emulsion was arranged from spherical and dispersed oil droplets to polyhedral packing of oil droplets adjacent to each other, while the LPI/XG mixtures changed from particles (in the uncrowded interfacial layer) to lamellae (in the crowded interfacial layer). When ϕ was 0.6, the emulsion was in a transitional state with the coexistence of particles and lamellar structures on the oil droplet surface. The LPI/XG-stabilized emulsions with ϕ values of 0.6-0.8 showed the highest stability during a 14-day storage period.

CONCLUSION

This study developed a promising plant-based protein resource, LPI, and demonstrates potential application of LPI/XG as an emulsifying stabilizer in foods. © 2023 Society of Chemical Industry.

Soy protein isolate-guar gum-goose liver oil O/W Pickering emulsions that remain stable under accelerated oxidation at high temperatures

BACKGROUND

Goose liver oil (GLO) is a solid-liquid mixture, rich in polyunsaturated fatty acids and high in nutritional value, but poor in fluidity and easily oxidized. Therefore, oil-in-water (O/W) Pickering emulsions of three polysaccharides and soy protein isolate (SPI) with GLO were prepared to improve the stability of it.

RESULTS

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy, and zeta potential revealed that the SPI and complexes with konjac glucomannan, pectin, and guar gum (GG) ranged from 17 to 75 kDa, with the site of action being the -OH stretch and the amide group, and bound by hydrogen bonding. Adding konjac glucomannan and GG significantly increased the water contact angle of the SPI to 74.1° and 59.0°, respectively. Therefore, the protein-polysaccharide complexes could enhance the emulsion stability. In addition, the O/W Pickering emulsions with GLO had near-Newtonian fluid rheological properties with a significant increase in apparent viscosity and viscoelasticity, forming a dual network structure consisting of a ductile and flexible protein network and a rigid and brittle polysaccharide network. The microstructure observation indicated that the O/W emulsions were spherical and homogeneous. The highest emulsification activity was observed for the SPI-GG-GLO emulsions, without significant delamination or flocculation and high oxidative stability after 7 days in storage.

CONCLUSION

These results demonstrate that the construction of SPI-GG-GLO O/W Pickering emulsions can stabilize GLO even at high temperatures that promote oxidation. © 2023 Society of Chemical Industry.

Advances in embedding techniques of anthocyanins: Improving stability, bioactivity and bioavailability

The health benefits of anthocyanins have attracted extensive research interest. However, anthocyanins are sensitive to certain environmental and gastrointestinal conditions and have low oral bioavailability. It has been reported that delivery systems made in different ways could improve the stability, bioavailability and bioactivity of anthocyanins. This present review summarizes the factors affecting the stability of anthocyanins and the reasons for poor bioavailability, and various technologies for encapsulation of anthocyanins including microcapsules, nanoemulsions, microemulsions, Pickering emulsions, nanoliposomes, nanoparticles, hydrogels and co-assembly with amphiphilic peptides were discussed. In particular, the effects of these encapsulation technologies on the stability, bioavailability and bioactivities of anthocyanins in vitro and in vivo experiments are reviewed in detail, which provided scientific insights for anthocyanins encapsulation methods. However, the application of anthocyanins in food industry as well as the biological fate and functional pathways in vivo still need to be further explored.

The colloid and interface strategies to inhibit lipid digestion for designing low-calorie food

Although fat is one of the indispensable components of food flavor, excessive fat consumption could cause obesity, metabolism syndromes and an imbalance in the intestinal flora. In the pursuit of a healthy diet, designing fat reducing foods by inhibiting lipid digestion and calorie intake is a promising strategy. Altering the gastric emptying rates of lipids as well as acting on the lipase by suppressing the enzymatic activity or limiting lipase diffusion via interfacial modulation can effectively decrease lipolysis rates. In this review, we provide a comprehensive overview of colloid-based strategies that can be employed to retard lipid hydrolysis, including pancreatic lipase inhibitors, emulsion-based interfacial modulation and fat substitutes. Plants-/microorganisms-derived lipase inhibitors bind to catalytic active sites and change the enzymatic conformation to inhibit lipase activity. Introducing oil-in-water Pickering emulsions into the food can effectively delay lipolysis via steric hindrance of interfacial particulates. Regulating stability and physical states of emulsions can also affect the rate of hydrolysis by altering the active hydrolysis surface. 3D network structure assembled by fat substitutes with high viscosity can not only slow down the peristole and obstruct the diffusion of lipase to the oil droplets but also impede the transportation of lipolysis products to epithelial cells for adsorption. Their applications in low-calorie bakery, dairy and meat products were also discussed, emphasizing fat intake reduction, structure and flavor retention and potential health benefits. However, further application of these strategies in large-scale food production still requires more optimization on cost and lipid reducing effects. This review provides a comprehensive review on colloidal approaches, design, principles and applications of fat reducing strategies to meet the growing demand for healthier diet and offer practical insights for the low-calorie food industry.

Research Progress of Protein-Based Bioactive Substance Nanoparticles

Bioactive substances exhibit various physiological activities-such as antimicrobial, antioxidant, and anticancer activities-and have great potential for application in food, pharmaceuticals, and nutraceuticals. However, the low solubility, chemical instability, and low bioavailability of bioactive substances limit their application in the food industry. Using nanotechnology to prepare protein nanoparticles to encapsulate and deliver active substances is a promising approach due to the abundance, biocompatibility, and biodegradability of proteins. Common protein-based nanocarriers include nano-emulsions, nano-gels, nanoparticles, and nano complexes. In this review, we give an overview of protein-based nanoparticle fabrication methods, highlighting their pros and cons. Additionally, we discuss the applications and current issues regarding the utilization of protein-based nanoparticles in the food industry. Finally, we provide perspectives on future development directions, with a focus on classifying bioactive substances and their functional properties.

Improving the Microstructural and Rheological Properties of Frozen Unfermented Wheat Dough with Laccase and Ferulic Acid

The quality deterioration that is induced by freezing treatment limits the development of frozen dough technology for standardized and delayed baking. In this study, laccase (LAC) and ferulic acid (FA) were employed to improve the rheological properties and microstructure of frozen unfermented dough. The results showed that the dough with LAC + FA had a lower softening degree than the dough with FA alone. Correspondingly, LAC + FA incorporation enhanced the viscoelastic behavior of frozen unfermented dough with better stability. Furthermore, a more uniform and homogeneous gluten network was observed in the LAC + FA-supplemented dough after 21 d of storage. The structural stability of the frozen gluten sample increased after LAC + FA treatment, possibly owing to an increase in the oxidation degree of FA. Moreover, LAC + FA treatment promoted the oxidation of the sulfhydryl groups to some extent, resulting in more extensive cross-linking. LAC + FA treatment hindered the protein conformational changes typically induced by frozen storage compared with LAC alone. Overall, LAC + FA treatment has a synergistic effect on enhancing the viscoelastic behaviors of frozen unfermented dough and inhibiting the conformational variation in frozen gluten; thus, it shows promise for improving frozen dough.

Understanding the structure, interfacial properties, and digestion fate of high internal phase Pickering emulsions stabilized by food-grade coacervates: Tracing the dynamic transition from coacervates to complexes

Although protein-polysaccharide complexes have shown tremendous potential in stabilizing high internal phase Pickering emulsions (HIPPEs), it is unclear whether coacervates have the same potential to be used as effective Pickering stabilizers. In this study, HIPPEs were prepared by ovalbumin (OVA)-pectin (PE) coacervates during the transition from coacervates to complexes. The results showed that enhanced OVA-PE interactions significantly affected the wettability and surface-tension reduction ability of the OVA-PE coacervates. At pH 2, the coacervate-stabilized HIPPEs exhibited smaller oil droplet sizes (21.3±2.3 μm), tighter droplet packing, and finer solid-like structures through the bridging of droplets and the generation of stronger gel-like network structures to prevent coalescence and lipid oxidation. The gastrointestinal digestion results proved that the OVA-PE coacervates promoted lipid hydrolysis and improved the bioaccessibility (from 19.7±0.7% to 36.5±2%) of curcumin-loaded HIPPEs. Our work provides new ideas for the development of biopolymer particles as effective Pickering stabilizers in the food industry.

Construction of vitamin D delivery system based on pine nut oil Pickering emulsion: effect of phenols

BACKGROUND

The food industry has begun to develop foods fortified with unsaturated fatty acids; however, the susceptibility of pine nut oil to oxidation and other properties limits its use in food production. Researchers often inhibit the oxidation of oil by adding antioxidants. After the combination of polyphenols and proteins, the complex formed can improve or enhance the performance of the emulsion when it stabilizes the emulsion. Encapsulating, protecting, and controlling the release behavior of vitamin D (V_D ) during digestion through an emulsion delivery system can effectively overcome limitations such as easy degradation during processing and storage. This research uses tannic acid, gallic acid, tea polyphenol, and vanillic acid to prepare Pickering emulsions, and the type of phenolic compound is explored by multi-dimensional characterization and the amount of emulsion.

RESULTS

The influence of traits, microstructure, stability, V_D load application, and effect on the emulsion matrix's encapsulation rate and bioaccessibility is studied. A method was investigated to enhance the oxidative stability of whey protein isolate-stabilized emulsions by introducing phenol. Pickering emulsions could be obtained in the presence of phenol, while the type of phenol played a relatively important role, probably because the mechanism involved interactions between particles. Viscosity and creaming stability of emulsions increased with crosslinking of phenol in emulsions. In addition, the presence of phenol in emulsions significantly increased the bioaccessibility of encapsulated V_D after in vitro digestion.

CONCLUSION

The method presented in this study was important for improving the oxidative stability of pine nut oil emulsions, expanding the application of pine nut oil in the food industry, and providing the theoretical and application basis of application and active substance emulsion delivery systems. © 2022 Society of Chemical Industry.

Pickering emulsions stabilized by zein-gallic acid composite nanoparticles: Impact of covalent or non-covalent interactions on storage stability, lipid oxidation and digestibility

Studies have shown that covalent and non-covalent zein-polyphenol complexes exhibit significant differences in structure and properties, but their effects on the characteristics of Pickering emulsions are still unclear. In this study, zein nanoparticles (ZNPs), non-covalent (N-ZGANPs) and covalent (C-ZGANPs) zein-gallic acid nanoparticles were fabricated to investigate the influence of complexation types on the properties of an algal oil-in-water Pickering emulsion. Results indicated that the addition of gallic acid was associated with the decrease of interfacial tension of particles. C-ZGANPs possessed the strongest interfacial adsorption capacity, which contributed to the optimum physical stability of the covalent emulsion during storage. The rheological experiment demonstrated that C-ZGANPs decreased the viscoelasticity of the emulsion, while N-ZGANPs showed the opposite effect. Moreover, the emulsions stabilized by C-ZGANPs significantly delayed the oxidation of the encapsulated algal oil, protected astaxanthin (AST) from heat, as well as increased the bioaccessibility of AST in simulated digestion.

Targeting Interfacial Location of Phenolic Antioxidants in Emulsions: Strategies and Benefits

It is important to have larger proportions of health-beneficial polyunsaturated lipids in foods, but these nutrients are particularly sensitive to oxidation, and dedicated strategies must be developed to prevent this deleterious reaction. In food oil-in-water emulsions, the oil-water interface is a crucial area when it comes to the initiation of lipid oxidation. Unfortunately, most available natural antioxidants, such as phenolic antioxidants, do not spontaneously position at this specific locus. Achieving such a strategic positioning has therefore been an active research area, and various routes have been proposed: lipophilizing phenolic acids to confer them with an amphiphilic character; functionalizing biopolymer emulsifiers through covalent or noncovalent interactions with phenolics; or loading Pickering particles with natural phenolic compounds to yield interfacial antioxidant reservoirs. We herein review the principles and efficiency of these approaches to counteract lipid oxidation in emulsions as well as their advantages and limitations.

Effect of chitosan-protocatechuic acid conjugate on stability and encapsulation capacity of polysaccharide-based high internal phase emulsion

The aim of this work was to fabricate chitosan-protocatechuic acid (CSPA) conjugates by free radical grafting method and use them as novel emulsifiers to inhibit lipid oxidation and delay the photodegradation rate of curcumin in polysaccharide-based high internal phase emulsions (HIPEs). Results of UV-vis, FT-IR and ¹H NMR spectra demonstrated that PA had been successfully bonded to chitosan (CS) through ester and amino linkages. CSPA conjugates (especially those with the ratio of CS to PA of 1:0.75) showed significantly increased water solubility and antioxidant activity than CS monomer. Furthermore, compared with sole OSA starch (OSAS), the electrostatic combination of CS and CSPA conjugate with OSAS could further reduce the interfacial tension, which was conducive to their adsorption at the oil-water interface. The introduction of CS and CSPA conjugate also increased the viscosity of aqueous phase and promoted the formation of gel-like percolating network structure, thereby effectively preventing droplets coalescence and endowing HIPEs with ideal viscoelasticity. More importantly, the contents of lipid hydroperoxide (24.09 μmol/g oil) and malondialdehyde (166.71 nmol/g oil) in HIPEs prepared by OSAS-CS-CSPA complexes were lower than those stabilized by OSAS, OSAS-CS and OSAS-CSPA complexes during accelerated storage. In addition, HIPEs prepared by OSAS-CS-CSPA complexes showed stronger protection capacity on curcumin against ultraviolet irradiation and natural light degradation. This study will provide useful information and technical reference for the fabrication of antioxidant polysaccharide-based HIPEs delivery vehicles.

Formation mechanism of Pickering emulsion gels stabilized by proanthocyanidin particles: Experimental and molecular dynamics studies

The feasibility of constructing a Pickering emulsion gel with proanthocyanidin particles (PAP) was evaluated in this study, and the related mechanism was revealed by combining instrumental characterization with molecular dynamics simulation. The results showed that PAP was composed of nano/micron spherical particles or their fragments, which had excellent wettability. Suitable PAP addition amount (w, ≥1%) and oil volume fraction (φ, 40-90 %) were beneficial to the formation of stable Pickering emulsion gel. The oil droplet size of gel was inversely proportional to w and φ. The mechanical parameters (gel strength, loss modulus, and storage modulus) were positively correlated with w and φ. Molecular dynamics simulation indicated that the proanthocyanidin molecules in the oil-water system could spontaneously reside and aggregate at the interface, and their interactions with water and oil reduced interfacial tension, which was consistent with the experimental results. This study provides a reference for other polyphenol-based Pickering emulsions.

Oxidation and oxidative stability in emulsions

Emulsions are implemented in the fabrication of a wide array of foods and therefore are of great importance in food science. However, the application of emulsions in food production is restricted by two main obstacles, that is, physical and oxidative stability. The former has been comprehensively reviewed somewhere else, but our literature review indicated that there is a prominent ground for reviewing the latter across all kinds of emulsions. Therefore, the present study was formulated in order to review oxidation and oxidative stability in emulsions. In doing so, different measures to render oxidative stability to emulsions are reviewed after introducing lipid oxidation reactions and methods to measure lipid oxidation. These strategies are scrutinized in four main categories, namely storage conditions, emulsifiers, optimization of production methods, and antioxidants. Afterward, oxidation in all types of emulsions, including conventional ones (oil-in-water and water-in-oil) and uncommon emulsions in food production (oil-in-oil), is reviewed. Furthermore, the oxidation and oxidative stability of multiple emulsions, nanoemulsions, and Pickering emulsions are taken into account. Finally, oxidative processes across different parent and food emulsions were explained taking a comparative approach.

The stability mechanism of Pickering emulsions fabricated by multi-functional amylose-based nanoparticles in a delivery system

In this work, multi-functional amylose-based nanoparticles (OSA-AM-9/VE NPs) were fabricated via simple and sustainable esterification, encapsulation, and co-precipitation processes of amylose (AM), octenyl succinic anhydride (OSA), and vitamin E (VE). These nanoparticles showed a nanometer size of 243.2 nm and a regular spherical shape which contributed to their excellent physical and oxidative stability and the outstanding pH-responsive performance of a Pickering emulsion. Compared with OSA-AM-9 and OSA-AM-9 NPs, the Pickering emulsion stabilized by OSA-AM-9/VE NPs presented higher stability and stronger antioxidant capacity. The delivery system of the OSA-AM-9/VE NP stabilized emulsion could protect fish oil from gastric juice and then was digested to facilitate the absorption of ω-3 polyunsaturated fatty acids in the intestine due to the pH-induced protonation/deprotonation of carboxyl groups in OSA-AM-9/VE NPs.

Stability of protein particle based Pickering emulsions in various environments: review on strategies to inhibit coalescence and oxidation

The emerging research interests in fabrication of protein particles as soft-particle emulsifiers show the prospective potential of using protein particles in novel poly-phase dispersing food systems. This review first provides a comprehensive summary and analysis on the dominant role of key physicochemical properties of protein particles including wettability, morphology, surface charge and protein concentration on their emulsifying abilities to construct Pickering emulsions. It was found that the constructed emulsions showed high sensitivity to changes in pH, ionic strength and temperature (thermal and freeze-thaw treatment). Moreover, oxidation remains as a challenge for protein particle based Pickering emulsions during prolonged storage, reducing their acceptance in food products. Current strategies for improving the stability of these emulsions to variable aqueous conditions and variable temperatures, and restricting oxidation event are summarized. In summary, an "ideal" protein particle-based Pickering emulsion system is proposed, encompassing aspects of interfacial property, emulsion network and texture, and antioxidant enrichment, thus promoting industrial translation into novel food and nutraceutical products.

Characterization of bacterial cellulose nanofibers/soy protein isolate complex particles for Pickering emulsion gels: The effect of protein structure changes induced by pH

In this work, the influence of soy protein isolated at different pH values (1-9) on the self-assembly behaviors of bacterial cellulose nanofibers/soy protein isolate (BCNs/SPI) colloidal particles via anti-solvent precipitation were investigated. The results showed that the formation of BCNs/SPI at pH values of 1-5 was mainly driven by electrostatic interaction, while the formation of those at pH values of 5-9 was driven by weak molecular interactions including hydrogen bonding and steric-hindrance effect. The FTIR demonstrated that the conformation of protein involved a transition from order to disorder at the level of secondary structure as pH values were away from the isoelectric point. The fluorescence spectroscopy and UV-vis adsorption spectroscopy indicated that hydrophobic region of SPI at pH value of 5 displayed more exposed as compared with that at pH values away from the isoelectric point. The changes in structure conformation of SPI induced by pH values led to the changes in properties of the BCNs/SPI colloidal particles including particle size, microstructure, crystallinity, hydrophily, thermal stability, and rheological properties. Furthermore, the structures of BCNs/SPI colloidal particles at different pH values significantly affected the stability of Pickering emulsion gels stabilized by the corresponding complex colloidal particles. This study provided a theoretical basis for the design of food-grade Pickering emulsion gels stabilized by BCNs/SPI complex colloidal particles.

Stability and digestibility of encapsulated lycopene in different emulsion systems stabilized by acid-modified soybean lipophilic protein

BACKGROUND

Owing to the harsh acidic environment of the stomach, acid-resistant emulsion products have wide-ranging applications in the food industry. Herein, natural soybean lipophilic protein (LP) was used to establish coarse emulsions, nanoemulsions, emulsion gels, and high internal phase Pickering emulsions (HIPPE) under acidic conditions. Furthermore, the carrying characteristics of the acid-resistant emulsion system with lycopene were explored.

RESULTS

Comparisons of particle sizes, potentials, microstructures, and rheology of the four carrier systems revealed that HIPPE has a single particle-size distribution, the largest zeta potential, and an elastic gel-like network structure. Comparison of encapsulation rates indicated that HIPPE had the best effect on encapsulating lycopene, reaching approximately 90%. The pH stability, storage stability, and simulated in vitro digestion experiments showed that the four emulsions that were stable under acidic conditions had good acid resistance. Among them, the acid-induced LP-stabilized HIPPE had the best storage stability and superior compatibility with the harsh acidic environment of the stomach, which not only achieved the purpose of delaying the release of lipids but also conferred better protection to lycopene in the gastric tract; moreover, it achieved the best bioavailability.

CONCLUSION

LP-stabilized HIPPE has the best stability and can yield better absorption and utilization of lycopene by the body. The results of this study are helpful for the development of acid-resistant functional emulsion foods that are conducive to the absorption of lycopene. © 2022 Society of Chemical Industry.

Waste Utilization: Physicochemical characteristics, stability and applications of emulsified Rana chensinensis ovum oil with waste extracts

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The physicochemical characteristics, stability, and potential application of emulsified Rana chensinensis ovum oil was explored.

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The emulsified Rana chensinensis ovum oil was stabilized by Rana chensinensis ovum protein isolates.

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The emulsified Rana chensinensis ovum oil with the waste protein isolates demonstrated promising antioxidation property.

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Oral delivery application of the emulsified Rana chensinensis ovum oil for quercetin delivery.

Rana chensinensis ovum (RCO) is the major waste/by-product of Oviductus Ranae. This study investigated physicochemical characteristics and stability of emulsified Rana chensinensis ovum oil (RCOO) with Rana chensinensis ovum protein isolates (RCOPI) by particle size, zeta potential, scanning electron microscopy (SEM), visual appearance, confocal laser scanning microscopy (CLSM), rheology and antioxidant capacity. The emulsified RCOO demonstrated great stability, antioxidant capacity and rheological properties. The potential application of the emulsified RCOO as a delivery system was studied using quercetin as an example. The stability of encapsulated quercetin was investigated through storage stability, thermal stability and photostability. The bioaccessibility of encapsulated quercetin was explored by in vitro digestion simulation experiments. The results showed the stability and bioaccessibility of quercetin encapsulated in emulsified RCOO was greatly improved. This study showed that the emulsified RCOO is a promising edible delivery system for hydrophobic bio-actives.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

Formation, Structure and stability of high internal phase Pickering emulsions stabilized by BSPI-C3G covalent complexes

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The HIIPPE was stabilized by BSPI-C3G covalent particles.

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HIPPEs stabilized with 74% (v/v) oil phase fraction have a stable gel-like state.

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HIPPEs stability was the best with the 3 % (w/v) BSPI-C3G particle concentration.

Food-grade high internal phase Pickering emulsions (HIPPEs) are stabilized by protein-based particles, which have attracted extensive attention due to their good gel-like structure. The black soybean isolate protein/cyanidin-3-O-glucoside (BSPI-C3G) covalent particles were used as a particulate emulsifier to form stable HIPPEs with oil phase fractions (74 % v/v) and low particle concentrations (0.5 %–3 % w/v) The particle size distribution and microstructure demonstrated that the BSPI-C3G covalent particles acted as an interfacial layer and surrounded the oil droplets. As the concentration of BSPI-C3G particles increased from 0.5 % to 3 %, the droplet size, elasticity, antioxidant capacity of the heated or stored HIPPEs more stable. So, the HIPPEs had the best stability with the BSPI-C3G particle at 3 % (w/v) concentration. These findings may extend the application of BSPI and C3G in foods and provide the guidelines for the rational design of food-grade HIPPEs stabilized by protein/anthocyanin complexes.

Systematic comparison of structural and lipid oxidation in oil-in-water and water-in-oil biphasic emulgels: effect of emulsion type, oil-phase composition, and oil fraction

BACKGROUND

Because many common foods are emulsions (mayonnaise, margarine, salad dressing, etc.), a better understanding of lipid oxidation is crucial for the formulation, production, and storage of the relevant consumer products. We prepared oil-in-water (O/W) and water-in-oil (W/O) emulgels, and their architecture was characterized before monitoring lipid oxidation under thermally accelerated conditions to systematically compare the effect of emulsion type, oil composition, and oil fraction on the structure and lipid oxidation in thee biphasic emulgel systems.

RESULTS

Higher susceptibility of lipids to oxidation (>2.5 times) was observed in the biphasic O/W and W/O emulgels than in soybean oil owing to an interfacial region. In the heterogeneous emulsion systems, W/O emulgels had oxidation resistance than O/W emulgels did. Compared with the oil-phase composition of high oleic sunflower, soybean, and flaxseed oils, oxidation sensitivity of emulsified lipids was significantly raised as the degree of unsaturation increased from 100.72 to 203.07. Moreover, increasing oil fraction from 75% to 85% led to an obvious increase in total oxidation in O/W emulgels but a decrease in W/O emulgels. In addition to emulsion size and oil unsaturation, viscoelasticity had a remarkable effect on the low-unsaturated oil oxidation (e.g. high oleic sunflower oil).

CONCLUSION

Physical and structural phenomena played important roles in lipid oxidation based on a mass transport principle. These findings provide novel information for designing the structures of emulsion gels for controlling lipid oxidation through the cooperation of both formulation and architecture principles. © 2022 Society of Chemical Industry.

Improvement of Storage Stability of Zein-Based Pickering Emulsions by the Combination of Konjac Glucomannan and L-Lysine

In this work, L-lysine (Lys) was employed together with konjac glucomannan (KGM) to fabricate zein colloidal particles (ZCPs) aimed at enhancing the storage stability of Pickering emulsions. With the addition of Lys, zein-Lys colloidal particles (ZLCPs) and zein-Lys-KGM (ZLKCPs) exhibited smaller particle size (133.64 ± 1.43, 162.54 ± 3.51 nm), polydispersity index (PDI) (0.10 ± 0.029, 0.13 ± 0.022), π value, and more adsorbed protein. Meanwhile, KGM underwent deamidation in an alkaline solution, so the emulsions stabilized by ZLKCPs exhibited a solid gel-like structure with higher storage modulus (G′) and loss modulus (G′′), leading to lower fluidity and better stability. The synergistic effects of Lys and KGM improved the stability of the emulsion. Hydrophobic interactions and hydrogen bonds were the main driving forces forming colloidal particles, which were determined by driving force analysis.