In this study, the gelatin crosslinked by Transglutaminase (TG) was applied to stabilize food-grade high internal phase emulsions (HIPEs) by a facile one-step method. The influence of TG crosslinking ...time on the molecular weight distribution of gelatin and the microstructure, thermal stability and rheological properties of the HIPEs were investigated. The results showed that TG crosslinking effectively promoted the production of high weight molecular. The obtained HIPEs exhibited a uniform droplet diameter and a good storage stability. An excellent thermal stability was achieved among the HIPEs stabilized by TG-crosslinked gelatin. After heating at 90 °C and 121 °C for 20 min, there was little change in microstructure and viscosity when the crosslinking time reached 4 h, implying that it could be stored at room temperature through high temperature sterilization. In the rheological analysis, the HIPEs showed a higher viscosity and lower frequency dependence with the extension of the crosslinking time, suggesting its potential application in three dimensional (3D) printing. The subsequent 3D printing experiments also confirmed that the HIPEs had a good printing performance, and some 3D printing models with different colors could be successfully obtained. This study provides a facile industrialized method for gelatin-based HIPEs with high thermal stability, and supplies theoretical guidance for its practical application.
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•High internal phase emulsions (HIPEs) were stabilized by TG crosslinked gelatin.•The obtained HIPEs had excellent storage stability.•TG-crosslinking time influenced the properties of the HIPEs.•TG crosslinking of gelatin effectively improved thermal stability of HIPEs.•The HIPEs showed an excellent performance in 3D printing.
We demonstrated soy protein isolate (SPI) at pH 3 is suitable for preparing edible HIPEs with internal phase of corn oil, even at protein concentration as low as 0.5% (w/v). The highest internal ...phase volume reached 90% (v/v). There was no remarkable difference in appearance of the HIPEs after heating, but phase separation happened after freeze-thaw treatment. Interestingly, no distinct difference can be found in appearance of the heated HIPEs with internal phase volumes of 85% and 90% after freeze-thawing thrice. All the HIPEs exhibit a solid-like behavior as revealed by the results that the G′ value was higher than G′′ value. The increased surface hydrophobicity after heating suggested interaction of protein can happen after emulsion heating. The confocal laser scanning microscope confirmed the interaction of SPI and emulsions. The HIPEs can be utilized to encapsulate β-carotene. The β-carotene retention in HIPEs was 74.1%, significantly higher than that in corn oil.
•SPI at pH 3 is able to stabilize HIPEs with internal phase volume up to 90%.•Heating significantly improved the freeze-thaw stability of SPI-stabilized HIPEs.•Protein interaction is responsible for the improved stability of HIPEs after heating.•β-Carotene stability was enhanced after encapsulation in the SPI-stabilized HIPEs.
There is increasing interest in the development of Pickering emulsions stabilized by food grade (nano) particles, due to their promising applications in food formulations. The work reports for the ...first time that starch nanocrystals (SNCs) prepared by sulfuric acid hydrolysis from native waxy maize starch exhibit a great potential to act as sole effective stabilizer for oil-in-water high internal phase emulsions (HIPEs). Relative to the native starch, the SNCs had more irregular and agglomerated morphology, and significantly higher crystallinity and hydrophobicity. The particle size and ζ-potential of the SNCs considerably varied with pH and/or ionic strength. The formation, microstructure and properties of stable HIPEs were characterized by visual observations, optical microscopy and dynamic oscillary measurements. The results indicated that at a given particle concentration in the continuous phase (1.0 wt%), stable and gel-like HIPEs were formed at oil internal phase (ϕ) values of 0.75–0.85; increasing the particle concentration led to the formation of gel-like HIPEs with stronger stiffness; in the absence of NaCl, stable and gel-like HIPEs were formed only at pH values of 5.0–10.0, and increasing the pH persistently decreased the emulsion size (and accordingly, increased the gel stiffness); increasing the ionic strength from 0 to 400 mM resulted in a progressive impairment of the emulsification performance, as well as of the formation of stable HIPEs. The findings would be of great relevance for the development of HIPEs stabilized by SNCs appropriate to be applied in the food formulations.
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•Starch nanocrystals (SNCs) were characterized in terms of structure and physicochemical properties.•The properties of SNCs were closely associated with the pH and/or ionic strength.•SNCs exhibited a great potential to perform as effective stabilizers for oil-in-water HIPEs.•Stable and gel-like HIPEs could be fabricated at appropriate conditions.•Electrostatic screening impaired the formation of stable HIPEs by SNCs.
Food proteins can be readily converted into particles and used to produce food grade Pickering emulsions, including normal Pickering emulsions (PEs) and high internal phase Pickering emulsions ...(HIPPEs). Plant and animal proteins and their complexes with polysaccharide and polyphenols are commonly used as Pickering particles. The ability of protein-based Pickering particles to stabilize PEs and HIPPEs depends on interaction between proteins and the complexed compounds. Protein and protein-based Pickering particles have shown to possess the ability to stabilize the HIPPEs which have internal phase ratio higher than 74%. Although the protein-based Pickering particles are used to stabilize both PEs and HIPPEs, there are significant differences in mechanism through which they are formed and stabilized. Although there are notable advances in linking-particle properties, migration and spreading of protein particles at the oil-water interface, reduction in interfacial tension with stability of PEs and HIPPEs; these aspects still need continued research. Pickering particles produced using proteins and their complexes are greatly affected by processing conditions and other compounds present in food. This aspect appears to be less rigorously researched, despite the substantial effect of processing parameters on the stability of PEs and HIPPEs. This review compiles and assesses the latest advances on production, characterization, application and stability of PEs and HIPPEs stabilized by protein and protein-based Pickering particles.
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•Different protein particles used for stabilized Pickering emulsion are reviewed.•Various latest applications of Pickering emulsions are illustrated in detail.•High internal phase Pickering emulsions (HIPPEs) are described in focus.•Perspective and limitation for food graded Pickering emulsion are discussed.
Gelatin (GE) modified by chitooligosaccharide (COS) through electrostatic interaction and hydrogen bond was applied to stabilize food-grade high internal phase emulsions (HIPEs) via a facile way. The ...influence of COS on rheological stability and practical food application of HIPEs was investigated. The interaction between GE and COS promoted a tighter connection between GE and COS, endowed the interfacial membrane with strong structure to anti-deformation, and prevented the accumulation of emulsion droplets by steric hindrance effect. Rheological analysis further proved that COS could lead to high viscosity, high elasticity, excellent oscillation performance, high recovery rate, great thixotropy and the strengthened structure of HIPEs, suggesting the outstanding rheological stability for three dimensional (3D) printing. Subsequent 3D printing on colored card and food confirmed that the obtained HIPE had good extrudability and printing performance. This study could provide important implications for the development of food-grade rheologically stable HIPE and promote the potential food application in rapid prototyping.
•Developed gelatin/chitooligosaccharide nano conjugates formed by strong interaction.•Prepared high internal phase emulsions containing uniform, stable droplets.•Emulsion has excellent elasticity, thermal stability, thixotropy and strength.•Emulsion has great extrudability and 3D printability in food application.
β-cyclodextrin (β-CD) modified by chitosan (CS) via electrostatic interactions and hydrogen bonds was used to fabricate high internal phase emulsions (HIPEs) for food 3D printing. The most promising ...ink for 3D printing was screened among HIPEs stabilized by polysaccharide complexes at CS concentrations of 0.08–0.40 wt% and pH values of 3–7. The β-CD/CD complexes formed by 1.20 wt% β-CD and 0.32 wt% CS at pH 5 possessed proper wettability and interfacial tension, forming an interfacial membrane, which could offer sufficient electrostatic repulsion and steric barrier against the coalescence of emulsion droplets. Rheological analysis indicated that HIPE stabilized by β-CD/CS complexes at 0.32 wt% CS and pH 5 has good printing potential in three stages of 3D printing: extrusion (shear-thinning behavior), recovery (excellent thixotropy), and self-supporting (sufficient storage modulus and yield stress). Subsequently, 3D printing results of plane and stereo models also demonstrated that HIPE stabilized by these complexes possessed the best printability. This study obtained food-grade inks with outstanding extrudability, recoverability and self-supporting properties by a simple and easy method, providing ideas and guidance for applying polysaccharide-based HIPEs in 3D printing.
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•Developed β-cyclodextrin/chitosan complexes formed by physical interactions.•Prepared high internal phase emulsions possessed uniform and stable droplets.•The rheology of emulsions was controlled by CS concentrations and pH values.•The emulsion had outstanding extrudability and printability in food 3D printing.
The complexes of soluble starch and whey protein isolate (WPI) were prepared and used to stabilize high internal phase emulsion (HIPE). Ultraviolet absorption and fluorescence analyses confirmed that ...the starch/WPI complexes were formed. These complexes were formed by hydrophobic interaction. Through appearance, micro-morphology, particle size, and rheological properties analyses, it was found that stable HIPE could be prepared by the starch/WPI complex when the addition of starch reached 7.5%. In addition, β-carotene in the WPI-stabilized HIPE was completely degraded after 72 h of ultraviolet irradiation, while β-carotene in the starch/WPI complex-stabilized HIPE still had a retention rate of 17.95%. Finally, the stability of the starch/WPI complex-stabilized HIPE was explored. The starch/WPI complex-stabilized HIPE was more stable in acidic environments, but the possible exception was the pI of the WPI. Particularly, this HIPE was stable at high ionic strengths. These results suggested that starch was able to improve the emulsifying ability of WPI.
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•The starch/whey protein isolate (WPI) complexes were formed.•The starch/WPI complexes were formed by hydrophobic interaction.•The starch/WPI complex had stronger emulsifying ability than the starch and WPI.•Starch/WPI complex-stabilized HIPE had better protection effect on β-carotene than WPI-stabilized HIPE.•Starch/WPI complex-stabilized HIPE was stable at high ionic strengths.
A route for creating edible 3D materials is the use of highly concentrated oil-in-water emulsions. In this study, a high internal phase Pickering emulsion (HIPPE) was prepared by centrifuging ...pre-emulsions at different CNC concentrations. We found that HIPPE with an internal phase volume fraction of 80% can be obtained at 0.5 wt% CNC concentration and 4000 g centrifugal force. The resultant HIPPE exhibited excellent storage stability, apparent shear-thinning behavior, and high solid viscoelasticity, and these properties were successfully applied to 3D printing. We further investigated the effects of pH and ionic strength on the formation and 3D printability of HIPPE. It was shown that HIPPEs can be successfully prepared under pH conditions ranging from 5 to 8, and ionic strength between 25 and 200 mM NaCl. Furthermore, we demonstrated that HIPPE was able to 3D-print selected shapes with high resolution and shape fidelity at pH 7 and 50 mM NaCl. This printed material opens new possibilities for future food manufacturing, nutrition delivery systems, and biomedical tissue engineering.
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•HIPPEs are produced using unmodified CNCs and without adding extra solid particles.•The volume fraction of HIPPE stabilized by 0.5 wt% CNCs is up to 80%.•HIPPEs exhibit excellent 3D printability due to viscoelastic solid-like behavior.•3D object based on HIPPEs with 0.5 wt% CNCs and 50 mM NaCl shows fine shape.
This paper attempted to construct a high internal phase emulsion (HIPE) through altering interfacial behaviors using the electrostatic interaction between positive chitosan and negative octenyl ...succinic anhydride (OSA) starch. The partial polysaccharide complex of OSA starch/chitosan was used to stabilize HIPE, which was able to adsorb at the oil droplet interface and prevent the coalescence of oil droplets. The wettability of OSA starch was enhanced with the addition of positively charged chitosan, leading to the formation of partial complexes. The impact of pH and concentration of chitosan on the droplet size, surface charge, and interface behavior were investigated, and the formation of the polysaccharide complex was further confirmed by atomic force microscopy. The presence of the OSA starch/chitosan complex facilitated the formation of stable HIPE with a gel-like structure and satisfactory centrifugal and oxidative stability. These results are useful to provide information for fabricating polysaccharide-based HIPE delivery systems, which may help expand their application in the food industry.
