Emulsion System Research Articles

Storage stability and antioxidant activity of astaxanthin and beta-carotene as affected by the architecture of O/W emulsions of milk proteins

Astaxanthin and β-carotene are among the potential anti-oxidant carotenoids with strong health promoting features. However, their sensitivity to light, heat and mechanical forces limit their application in food processing and storage conditions. The design of food matrix system, such as emulsions, that could prevent them from exposure to environmental factors will be utmost importance to slow down their degradation. In this study, O/W emulsion systems containing sunflower oil were prepared by applying ultrasound treatment and using different stabilizers (i.e. whey protein isolate (WPI) and sodium caseinate; NaCAS), co-surfactants (pectin and lecithin) while their performance against physical and chemical stability were investigated. The WPI– lecithin system produced emulsion droplets with Average diameter in the range of 560–2900 nm with a zeta-potential in the range of (−31) – (−34) mV, whereas the NaCAS – lecithin systems produced emulsion droplets with average diameter in the range of 230–240 nm and zeta potential of (−44) – (−48) mV. These values have a direct effect on the physical stability and chemical stability of the carotenoids in the emulsions. Astaxanthin was found to be more sensitive than β-carotene to ultrasound processing conditions. The designed emulsion systems slowed down the degradation of the carotenoids and maintained their DPPH scavenging properties during storage with astaxanthin loaded emulsions exhibiting better DPPH activity than β-carotene loaded emulsions.

Encapsulation of Hydrophobic-but-Not-Lipophilic Perfluoro Liquids Based on a Self-Assembled Double Emulsion Template via Solvent Evaporation Method.

The facile encapsulation of perfluoro liquids that are hydrophobic but not lipophilic into liposomes or microcapsules presents a significant challenge in the fields of biomedicine, dynamic optics, functional chemical applications, etc. This is due to their chemical inertness and physical immiscibility, particularly those with low boiling points. In this study, a novel strategy based on a double emulsion template via solvent evaporation is proposed after investigating the mechanism of three-phase emulsion systems. The perfluoro liquid droplets can be easily emulsified into a polymer solution as the second emulsion layer, where the polymer shell is formed during solvent evaporation in the continuum medium under proper processing controls. The morphology of particles is predictable and fits well with the linear model derived from Neumann's triangle in three-phase systems. Furthermore, a comprehensive study on the encapsulation of perfluoro ketone, which is widely used as a green fire extinguisher agent, is conducted as an example. The encapsulated perfluoro ketone showed instant thermal response upon heating while maintaining a good shelf life at room temperature. The remarkable fire suppression performance exhibited great potential for practical applications. This work offers more insight into the encapsulation of "naughty" perfluorinated chemicals and provides more possibilities for extended applications.

Enhancement of catechin loaded in BSA-pullulan nanoparticles on the oxidation stability of pickering emulsion: Effect of concentration

Preventing and delaying the lipid rancidity especial O/W emulsion system is an important task in the food industry. Low solubility in aqueous/lipid phases and poor stability of catechins limited the antioxidant effect in O/W emulsion. To enhance the oxidative stability of O/W emulsions, bovine serum albumin (BSA)-pullulan (PUL) nanoparticles (BPNs) and catechins-loaded BPNs (BPCNs) were successfully fabricated via self-assembly in this paper. Fourier transform infrared (FTIR) spectra of BPNs and BPCNs indicated that self-assembly of BSA and PUL to form nanoparticles and loading of catechins in BPNs are all maintained through non-covalent interactions. Particle size distribution, zeta-potential, structural characterization and interfacial properties of BPNs and BPCNs showed that catechins act as cross-linking “bridge” among BSA molecules, leading to an increase in the mean particle size, surface charges, interfacial properties, radical scavenging activity of BSA-PUL nanoparticles. Compared with BPNs, BPCNs can significantly enhance the storage stability and oxidative stability of Pickering emulsions. In conclusion, enhancement of BPCNs on oxidative stability of the Pickering emulsions not only because of the radical scavenging activity of the loaded catechins, but also attributed to the effect of catechin loading on the increased interfacial charge and balanced the amino acids distribution of BSA in the BPCNs. This study highlights the excellent properties of BSA-pullulan-catechin nanoparticles as novel emulsifiers with high antioxidant activity and potential applications in the food industry.

Effect of cationized guar gum on stability and bioaccessibility of curcumin-loaded Pickering emulsion stabilized by starch nanoparticles

To enhance stability and bioaccessibility of curcumin in Pickering emulsions stabilized by starch nanoparticles (SNP), cationized guar gum (CGG) was incorporated into the emulsion. Zeta potential results revealed that SNP and CGG formed electrostatic interactions, resulting in stable interfacial layer with higher hydrophobicity. Adding 0.4 % CGG maintained a homogeneous phase without significant droplet size change for up to one month. The emulsion with 0.4 % CGG demonstrated stable storage under varying pH (4–10), ionic strength (0–10 mM NaCl), and freeze-thaw cycles (up to 3). When optimized Pickering emulsion system was applied to curcumin encapsulation, curcumin-loaded emulsions were stably maintained for up to one month. The curcumin retained approximately 100 % stability under thermal (90 °C) and UV (12h) treatments. In the optimized emulsion, starch components resisted digestion in oral and gastroenteric phases but were primarily digested in small intestine, resulting in an increasing bioaccessibility from 88.23 to 96.92 %.

High-efficiency bioconversion of phytosterol to bisnoralcohol by metabolically engineered Mycobacterium neoaurum in a micro-emulsion system.

21-Hydroxy-20-methylpregn-4-en-3-one (4-HBC, bisnoralcohol) is a crucial intermediate for the synthesis of steroidal drugs. Significant challenges including by-products formation and poor substrate solubility were still confronted in its main synthetic route by microbial conversion from phytosterol. Construction of a direct bioconversion pathway to 4-HBC and an efficient substrate emulsion system is therefore urgently required. In this study, three novel isoenzymes of 3-ketosteroid-Δ1-dehydrogenase (KstD) and 3-ketosteroid 9α-hydroxylase (KsH) in Mycobacterium neoaurum were excavated and identified as KstD4, KstD5, and KsHA3. A strain capable of fully directing the synthesis of 4-HBC was metabolically engineered via serial genetic deletion combined with enhanced expression of cholesterol oxidase (ChOx2) and enoyl-CoA hydratase (EchA19). Moreover, a micro-emulsion system combined with soybean oil and hydroxypropyl-β-cyclodextrin improved substrate solubility and bioavailability. In batch fermentation, molar yield of 96.7% with 39.5 gL-1 4-HBC was obtained from 50 gL-1 phytosterol. Our findings demonstrate the potential for industrial-scale biosynthesis of 4-HBC.

Magnetic polydopamine nanoparticles as stabilisers for enzyme-Pickering emulsions: Application in the interfacial catalytic reaction of olive oil

Solid particles are essential for stabilising Pickering emulsions and improving interfacial catalytic reactions. We constructed magnetic polydopamine nanoparticles to stabilise lipase-Pickering emulsions for olive oil deacidification. The results showed that the nanoparticles had a core-shell structure with an average particle size of 605.8 nm, a zeta potential of −39.3 mV and a contact angle of 55.9°, which effectively stabilised the emulsion. The particles were added to the lipase solution and sonicated to construct the emulsion system. The emulsion droplets were the smallest and most uniformly distributed under 400 W ultrasonic irradiation for 10 min. The lipase adsorbed on the oil-water interface and promoted the hydrolysis of olive oil. The released fatty acid content increased 1.7-fold compared with the non-emulsion. This study not only provides a new immobilisation method for the interfacial catalysis of lipase but also provides ideas for the high-value utilisation of high acid-value oil resources.

A CO2-responsive Janus SiO2 nanofluid: Integration of enhanced oil recovery and demulsification

Aiming to address the issues of limited suitability of conventional chemical oil displacement materials for formation conditions and the serious emulsification of oil and water in the produced liquid, the innovative nano oil-displacing system with CO2-responsive behavior has been developed. This system integrates oil displacement and emulsion breaking. The efficacy of the CO2-response system in creating stable emulsions with a high capacity to decrease interfacial tension has been demonstrated. The interfacial responsive behavior of all active components, including Janus nanoparticles, sodium oleate, gums, and asphaltenes, in the emulsion system was analyzed in terms of interfacial rheology and adsorption. Additionally, the prepared system demonstrated a rapid response to CO2, effectively breaking the emulsion within 5 min. Furthermore, the oil recovery enhancing mechanism of the CO2-response system was investigated using a microscopic visualization model. The system was proved to be efficient in initiating the residual oil within pore channels. Considering the combined effectiveness of the CO2-response system in terms of efficient oil displacement and rapid response, it offers valuable insights for advancing the chemical flooding technology of in enhanced oil recovery.

Optimization of Volumetric Ratio of Soy Milk and Concentration of Porang Gel on the Properties of Soy Milk Fortified with Ginger Extract

Soy milk is a typical soy protein product and a good source of essential nutrients, however “beany” off-flavor makes soy milk unpleasant or unacceptable to many consumers. The addition of ginger extract in this research is intended to mask the “beany” off-flavor in soy milk. Soy milk is a beverage with an emulsion system that exhibits unstable characteristics during storage. Creaming and sedimentation in protein-rich beverages can be addressed by enhancing system stability using polysaccharides such as glucomannan from the porang plant. Glucomannan has the ability to bind water effectively, restricting molecular movement and thereby improving the stability of soy milk. The objective of this research is to determine the optimal values for volumetric ration of soy milk and concentration of porang gel that yield the desired responses in terms of physical stability, viscosity, and antioxidant activity of soy milk using response surface methodology. The models predicted that the optimal formula was soy milk volumetric ratio of 69.3 (v/v) and porang gel concentration of 1.3%. The verification experiments were conducted in three replications. The results showed that physical stability, viscosity and IC50 value of soy milk were 0.90±0.05, 132.0±5.5 cP and 187.5±35.2 ppm under optimal formulation. The optimization results were validated and found no statistically significant differences at a 5% significance level. Soy milk with good physical stability, viscosity, and antioxidant activity can be prepared with this formulation.

Effects of ultrasonic treatment on the structure and functional characteristics of myofibrillar proteins from black soldier fly

In the process of utilizing black soldier fly larvae (BSFL) lipids to develop biodiesel, many by-products will be produced, especially the underutilized protein components. These proteins can be recycled through appropriate treatment and technology, such as the preparation of feed, biofertilizers or other kinds of bio-products, so as to achieve the efficient use of resources and reduce the generation of waste. Myofibrillar protein (MP), as the most important component of protein, is highly susceptible to environmental influences, leading to oxidation and deterioration, which ultimately affects the overall performance of the protein and product quality. For it to be high-quality and fully exploited, in this study, black soldier fly myofibrillar protein (BMP) was extracted and primarily subjected to ultrasonic treatment to investigate the impact of varying ultrasonic powers (300, 500, 700, 900 W) on the structure and functional properties of BMP. The results indicated that as ultrasonic power increased, the sulfhydryl content and turbidity of BMP decreased, leading to a notable improvement in the stability of the protein emulsion system. SEM images corroborated the changes in the microstructure of BMP. Moreover, the enhancement of ultrasound power induced modifications in the intrinsic fluorescence spectra and FTIR spectra of BMP. Additionally, ultrasonic treatment resulted in an increase in carbonyl content and emulsifying activity of BMP, with both peaking at 500 W. It was noteworthy that BMP treated with ultrasound exhibited stronger digestibility compared to the untreated. In summary, 500 W was determined as the optimal ultrasound parameter for this study. Overall, ultrasound modification of insect MPs emerges as a dependable technique capable of altering the structure and functionality of BMP.

Stability and gastrointestinal digestion behaviour of theaflavins encapsulated in W/O Pickering emulsions

Theaflavins (TFs) are naturally bioactive compounds with low stability and poor bioavailability. In this study, the stability of TFs during storage at 25 °C for 21 d and thermal treatments at 65 °C, 85 °C and 105 °C for 0.5–4 h of water in oil (W/O) Pickering emulsions composed of TFs (0–9 mg/g), ursolic acid, oil and water were investigated. The TFs incorporation at 9 mg/g had the smallest droplet size and the highest G′ and G″ values. After storage for 21 days and thermal treatment at 105 °C for 4 h, the TFs retention in emulsions (9 mg/g) were 1.2-fold and 1.4-fold higher than aqueous solution, respectively, which might be attributed to the encapsulation of TFs in water droplets. During digestion, TFs emulsions provided a greater surface area for lipid digestion and led to a higher release of free fatty acids than emulsions without TFs. Moreover, there was sustained release of TFs in the emulsion, resulting in significantly enhanced TFs bioaccessibility (57.8 ± 9.2%) compared with aqueous solution (17.7 ± 1.1%) and Oil-Water mixture (32.6 ± 2.3%) after intestinal digestion. This study provides insights for food industry in designing W/O emulsion systems for the delivery of hydrophilic bioactive components.

3D-Printed Interfacially Jammed Emulsion Aerogels.

3D printing ultralightweight porous structures using direct ink writing (DIW) while maintaining their mechanical robustness is highly challenging. This difficulty is amplified when low ink concentrations are used to create complex geometries. Herein, this shortfall was addressed by interfacially jammed emulsion gels. The gel emerged from the electrostatic interaction among synergized nanomaterials (graphene oxide (GO) and cellulose nanocrystals (CNCs)) in the aqueous phase and a ligand in the oil phase. This interaction led to the jamming of the nanoparticles and the creation of stable emulsion gels. The formed interfacial assemblies were further treated by post-jamming ionic cross-linking with NaHCO3, which dictated the emulsion gels' rheological characteristics, enhancing the ink's viscoelastic properties for high-resolution 3D printing. The customizable emulsion system allows control over porosity from the macro- to the micro-scale and generates complex geometries with desired compositions. By manipulating post-annealing processes and varying concentrations, it is possible to achieve aerogels that feature a remarkably low density (∼2.63 mg/cm3) and adjustable mechanical robustness (elastic modulus of 0.45 MPa). Additionally, this method allows for producing aerogels with flexible or stiff characteristics as required, alongside the capability to tailor specific electromagnetic shielding effectiveness (ranging from 6791 to 19615 dB cm2/g), showcasing the technique's versatility and engineerability.

Effect of a Natural Surfactant (Fenugreek Seeds) on Emulsification and Mobilization of Paraffins via Pore-Scale Micromodel Experiments.

The surface characteristics of minerals have been crucial in predicting the interactions between chemicals, particularly in chemical flooding. Thus, this paper evaluates the viability of natural surfactants derived from agricultural products for oil recovery studies using a micromodel filled with paraffinic oil. The study investigates the interfacial tension, viscosity, microscopic, dilution, and oil mobilization characteristics of the natural surfactants. The experimental setup involves conducting interfacial tension measurements between the surfactant solution and paraffinic oil using the Wilhelmy plate method and was found to be 14.2, 10.92, and 9.8 mN/m. Additionally, viscosity measurements and frequency sweep analysis were performed to assess the rheological properties of the prepared emulsion, which was stabilized using a natural surfactant. Microscopic evaluation depicts that, among the prepared emulsions, n-heptane emulsion seems more stable at both 30 and 90 °C. Moreover, dilution studies were conducted for each emulsion system, and the dilution ratio was varied from 1:5 to 1:1 (emulsion/saline solution). It was found that n-heptane emulsion possesses better stability at higher dilution (until a 3:5 ratio). Oil mobilization studies are conducted using a glass micromodel to simulate reservoir conditions and observe the displacement efficiency of the surfactant solutions. The results indicate that natural surfactants exhibit competitive interfacial tension reduction and viscosity modification properties compared to commercial surfactants. Furthermore, oil mobilization studies demonstrate the effectiveness of natural surfactants in enhancing oil recovery from paraffinic oil reservoirs. These findings suggest the potential of natural surfactants derived from agricultural products as sustainable alternatives for improving the oil recovery efficiency in petroleum reservoirs.

Effect of silica nanoparticles on crude oil emulsions stabilized by a natural surfactant from Fenugreek Seeds and polyacrylamide for subsurface oil mobilization applications

Emulsions represent a sustainable method for subsurface resource recovery due to their superior performance in pore plugging, mobility control and interfacial tension reduction. However, the stability of emulsion plays a vital role in determining the success of field implementation. In this work, a novel formulation is reported for emulsions wherein they have been stabilized by natural surfactant extracted from fenugreek seed. In this work, two emulsion systems are reported, that is surfactant polymer and nanoparticle-surfactant-polymer emulsion. Surfactant-polymer emulsions are stabilized by natural surfactant whereas nanoparticle-surfactant-polymer emulsion are stabilized in presence of nanoparticle and natural surfactant. Both the emulsions exhibit shear thinning profile as observed from rheological studies. Nanoparticle-surfactant-polymer emulsions were found to be thermally stable than that of Surfactant-polymer emulsions as evident from microscopic and rheological studies. An increase in temperature has the unfavorable impact on surfactant-polymer emulsion as huge drop in viscosity profile was observed. The viscosity profiles of nanoparticle-surfactant-polymer emulsions were found to be best fitted by the Krieger-Dougherty model with the value of coefficient correlation R2 = 0.99. The contact angle studies showed that NSP solution can reduce the contact angle to much lower value, which is 111˚ to 30˚ whereas surfactant-polymer solution was able to reduce from 116˚ to 57˚ only. Adsorption of silica nanoparticle was also observed in presence of sandstone and decrease in 27.32 % of peak absorbance was observed in span of 20 days. Therefore, finding of the study indicates that nanoparticle-surfactant-polymer emulsions has potential to perform better than surfactant-polymer emulsions, even at elevated temperature, and can be a better and cost-effective alternative to the conventional emulsions used in oilfield applications.

Effects of soybean-oil and emulsifiers mixture on rheological properties of oil-in-water emulsions

The effects of soybean-oil and emulsifiers mixture on rheological properties of oil-in-water emulsions were investigated. Polysorbate-80 and sorbitan-monooleate in the ratio 1:3 were added to stabilize a soybean-oil emulsion by high-pressure homogenization at 50 and 100 MPa. Particle size and rheological properties were measured. The z-average size value showed all the droplets ranging from 295.5 to 302.3 nm. The emulsions were Newtonian and non-Newtonian pseudoplastic at 50 MPa, although at 100 MPa exhibited a Newtonian behavior, preferably. The highest concentrations of soybean-oil and emulsifiers mixture showed semi-solid emulsions (at 50 MPa), and the lower concentrations of soybean-oil and emulsifiers mixture, showed semi-solid emulsions (at 100 MPa), however, elastic character predominated over viscous character (G’>G’’), for both pressures. In conclusion, the emulsion systems were nanoemulsions and their droplet size distribution was bimodal. The nanoemulsions had a non-Newtonian behavior for both pressures, although at 100 MPa the emulsions were Newtonian.

Oil in water emulsion stabilized by glycated rice bran protein aggregates: Effect on interfacial behavior and in vitro digestion of emulsion

To investigate the effect of molecular weight of saccharides and heating time on interfacial behavior of protein, glycated rice bran protein aggregates (gRBPAs) were obtained by incubating rice bran protein (RBP) with glucose (Glu), maltose (Mal) and dextran (Dex) via acid-heat treatment (pH 2.0, 90 °C). Subsequently, the stability and in vitro simulated digestion properties of oil in water (O/W) emulsion stabilized by gRBPAs were analyzed. Structural analysis (circular dichroism and fluorescence spectra) proved that the tertiary structure and secondary structure of RBP changed after glycation, and the contents of β-sheet structure of gRBPAs increased significantly. Besides, the glycation improved the interfacial activity and emulsification of protein obviously. Compared with Glu or Mal, the grafting of Dex could produce larger steric hindrance, which better inhibited the aggregation of emulsion droplets. Furthermore, glycation enhanced the pancreatic lipase (PL) inhibitory activity of gRBPAs obviously, and the emulsions stabilized by gRBPAs exhibited higher anti-digestion ability (62.12–75.00%) compared with RBP (95.27%). Moreover, the free fatty acid (FFA) rate of O/W emulsion was closely related to the surface hydrophobicity, degree of glycation, PL inhibitory activity and interfacial behavior of gRBPAs. Therefore, these findings would be enlightening to intuitively tailor the physicochemical stability and digestibility of O/W emulsion system according to heating time and molecular weight of saccharides. Meanwhile, this work would facilitate the application of O/W emulsion stabilized by glycated protein aggregates in functional foods.

Application of resveratrol on oxidative stability of protein-based Antarctic krill oil high internal phase emulsion

Antarctic krill oil (KO) is known for its poor oxidative stability, especially in emulsion systems. In this experiment, a complex of scallop water-soluble protein-resveratrol (SWPs-RES) was mixed with KO to create high internal phase emulsions (HIPEs) with varying RES ratios. The addition of RES led to noticeable conformational changes in SWPs, including fluorescence bursts, alterations in secondary structure, and modifications in binding motifs. The SWPs-RES complex (1:0.2) demonstrated the most effective free radical scavenging activities (HO: 38.61%, DPPH: 72.49%, ABTS: 85.66%), while the SWPs-RES complex (1:0.025) exhibited the highest emulsifying capacity. Furthermore, HIPEs containing the SWPs-RES complex (1:0.2) displayed improved rheological properties, physical stability, and enhanced oxidative stability against lipid oxidation during storage and simulated in vitro digestion. This study lays a scientific foundation for the utilization of scallop protein and Antarctic krill oil in the food industry.

Quercetin slow-release system delays starch digestion via inhibiting transporters and enzymes

This study investigates the potential of a quercetin-based emulsion system to moderate starch digestion and manage blood glucose levels, addressing the lack of in vivo research. By enhancing quercetin bioaccessibility and targeting release in the small intestine, the emulsion system demonstrates significant inhibition of starch digestion and glucose spikes through both in vitro and in vivo experiments. The system inhibits α-amylase and α-glucosidase via competitive and mixed inhibition mechanisms, primarily involving hydrogen bonds and van der Waals forces, leading to static fluorescence quenching. Additionally, this system downregulates the protein expression and gene transcription of SGLT1 and GLUT2. These findings offer a novel approach to sustaining glucose equilibrium, providing a valuable foundation for further application of quercetin emulsion in food science.

Experimental study on enhanced oil recovery of acidic heavy oil by in situ O/W emulsion flooding

Heavy oil in this work is typical acidic heavy oil with acid number larger than 1, which is prone to form W/O emulsions with high viscosity and cause low oil recovery factor during water flooding. In order to further improve oil recovery of acidic heavy oil after water flooding, this paper proposed the in situ O/W emulsion flooding to conversely transform W/O emulsions into O/W emulsion with lower viscosity. Firstly, emulsion system compounding (SDS:L5 = 1:1) named ISEMF was comparatively obtained, which could decrease IFT into magnitude of 10−2 mN/m and inversely form stable O/W emulsions with low viscosity. The emulsion evaluation experiment indicated that W/O emulsion would be reversed into O/W emulsions when ISEMF concentration and water content were larger than 0.4% and 30%. Core displacement experiments showed recovery factor increment firstly increased and then decreased with permeability, and there was optimal permeability range for in situ emulsion flooding. The main reason was that much lower or larger permeability was not beneficial to good matching of emulsion droplet and pore throat. In addition, it was found that the displacement efficiency of in situ O/W emulsion flooding was better than that of surfactant flooding under the same conditions, which further validate excellent EOR performance of in situ O/W emulsion flooding for acidic heavy oil.

W/O/W Pickering emulsions stabilized by complex modified phycocyanin.

A water-in-oil-in-water (W/O/W) double emulsion can simultaneously load hydrophilic and hydrophobic substances due to its unique two-membrane, three-phase structure. However, thermodynamic instability greatly limits the application of double emulsions in food processing. Further development of Pickering emulsions based on proteins, etc., can improve the stability and loading capacity. It is of great significance to promote their practical application. Herein, we prepared ultrasound pretreatment complex glycation-modified phycocyanin (UMPC) to stabilize a W/O/W Pickering emulsion for the codelivery of vitamin B12 (VB12) and vitamin E (VE). First, an inner water phase and oil phase containing polyglycerin polyricinoleate were homogenized to prepare a W/O emulsion. Subsequently, the W/O emulsion was homogenized with an outer water phase containing UMPC to obtain a W/O/W Pickering emulsion. A gel-like inner phase emulsion with excellent storage and thermal stabilities was obtained under the condition that the W/O emulsion volume ratio was 80% and the UMPC was stabilized by 10 g kg-1. The double emulsion after loading VB12 and VE showed good encapsulation effect during the storage period, the encapsulation rate could reach more than 90%, it also showed excellent protection effect under long-time storage and UV irradiation and the retention rate increased by more than 65%. In addition, the bioavailability of VB12 and VE significantly increased during simulated gastrointestinal digestion and reached 46.02% and 52.43%, respectively. These results indicate that the UMPC-stabilized W/O/W Pickering emulsion is an effective carrier for the codelivery of hydrophilic and hydrophobic bioactive molecules and also provides a means for useful exploration of an efficient and stable emulsion system stabilized by biological macromolecules. © 2024 Society of Chemical Industry.

Insight into the role of droplets in quinoa starch-based Pickering high internal phase emulsion for enzymatic hydrolysis reaction

Pickering high internal phase emulsion has emerged as potential platforms for biocatalytic reactions. Herein, native quinoa starch was used as the emulsifier to form a stable Pickering HIPE with an internal phase up to 80 %. The catalytic performance of lipase loaded in HIPE was evaluated for the enzymatic hydrolysis of hexyl hexanoate. Compared with the typical Pickering emulsion, biphasic, and monophasic systems, the Pickering HIPE system displayed higher conversion (83.54 % at 1440 min) and specific enzyme activity (1.41 U/mg), thus emphasizing the crucial role of microdroplets and large interface area created by both the starch particles and high internal phase volume. Subsequently, HIPEs with different starch concentrations were fabricated to further understand the catalysis behavior happening at compartmentalized microdroplets and interfaces. The microstructural, interfacial, and rheological properties of the HIPEs were systematically determined to explain the correlation between emulsion properties and catalytic efficiency. High starch concentration reduced the droplet size and increased the interfacial area, thus shortening the mass transfer distance and enlarging the reaction area. Meanwhile, the increased surface coverage and viscosity led to poor accessibility and limited mass movement. This trade-off made the maximum conversion be obtained at 2 wt% concentration. The study provides novel information about the role of emulsion droplets in the catalytic performance of lipase in starch-based HIPE.