Droplet Aggregation Research Articles

Transcriptomics Reveals the Mechanism of Rosa roxburghii Tratt Ellagitannin in Improving Hepatic Lipid Metabolism Disorder in db/db Mice.

A complex metabolic disorder, type 2 diabetes, was investigated to explore the impact of ellagitannin, derived from Rosa roxburghii Tratt (RTT), on liver lipid metabolism disorders in db/db mice. The findings demonstrated that both RTT ellagitannin (C1) and RTT ellagic acid (C4) considerably decelerated body mass gain in db/db mice, significantly decreased fasting blood glucose (FBG) levels, and mitigated the aggregation of hepatic lipid droplets. At LDL-C levels, C1 performed substantially better than the C4 group, exhibiting no significant difference compared to the P (positive control) group. An RNA-seq analysis further disclosed that 1245 differentially expressed genes were identified in the livers of experimental mice following the C1 intervention. The GO and KEGG enrichment analysis revealed that, under ellagitannin intervention, numerous differentially expressed genes were significantly enriched in fatty acid metabolic processes, the PPAR signaling pathway, fatty acid degradation, fatty acid synthesis, and other lipid metabolism-related pathways. The qRT-PCR and Western blot analysis results indicated that RTT ellagitannin notably upregulated the gene and protein expression levels of peroxisome proliferator-activated receptor alpha (PPARα) and peroxisome proliferator-activated receptor gamma (PPARγ). In contrast, it downregulated the gene and protein expression levels of sterol regulatory element-binding protein (SREBP), recombinant fatty acid synthase (FASN), and acetyl-CoA carboxylase (ACC). Therefore, RTT ellagitannin can activate the PPAR signaling pathway, inhibit fatty acid uptake and de novo synthesis, and ameliorate hepatic lipid metabolism disorder in db/db mice, thus potentially aiding in maintaining lipid homeostasis in type 2 diabetes.

Wetting vs Droplet Aggregation: A Broadband Rotational Spectroscopic Study of 3-Methylcatechol ⋯ Water Clusters.

Two competing solvation pathways of 3-methylcatechol (MC), an atmospherically relevant aromatic molecule, with up to five water molecules were explored in detail by using a combination of broadband rotational spectroscopy and computational chemistry. Theoretically, two different pathways of solvation emerge: the commonly observed droplet pathway which involves preferential binding among the water molecules while the solute serves as an anchor point for the formation of a water cluster, and an unexpected wetting pathway which involves interactions between the water molecules and the aromatic face of MC, i.e., a wetting of the π-surface. Conclusive identification of the MC hydrate structures, and therefore the wetting pathway, was facilitated by rotational spectra of the parent MC hydrates and several H218O and 13C isotopologues which exhibit splittings associated with methyl internal rotation and/or water tunneling motions. Theoretical modelling and analyses offer insights into the tunneling and conversion barriers associated with the observed hydrate conformers and the nature of the non-covalent interactions involved in choosing the unusual wetting pathway.

Modulating in vitro gastrointestinal digestion of nanocellulose-stabilized pickering emulsions by altering particle surface charge

An in vitro model of human gastrointestinal digestion was introduced to investigate the effects of surface charge of cellulose nanoparticles on emulsion structure during gastric phase, lipase activity, bile salt diffusion, and free fatty acid (FFA) release. Four carboxymethylated cellulose nanofibrils (CNF; C0, C0.36, C0.72, and C1.24) were used, showing different surface charge (p < 0.05). First, four carboxymethylated CNFs had no inhibition effects on lipase activity and bile salt diffusion. Moreover, we found that the lipid emulsion containing CNF formed gel structure to induce oil droplets aggregation during simulated gastric phase. Additionally, the particle surface charge greatly influenced the gel structure of emulsion where a denser gel structure was observed in the C0 (lowest surface charged CNF) stabilized emulsion. Finally, the released FFA results showed that the formed gel structure lowered the lipid emulsion digestion attributed to the restricted adherent area of oil droplets for lipase and bile salt.

Effect of wheat aleurone on lard emulsions during in vitro digestion

Dietary wheat aleurone has been shown to affect lipid metabolism and reduce the incidence of obesity. However, the underlying mechanisms are not fully understood. This work aimed to investigate how whole wheat aleurone affects lipolysis during the whole digestion process in vitro. The physicochemical and microstructural changes and the lipolysis kinetics of different lard emulsion mixtures were determined. The results showed that the lipolysis rate and degree are inversely proportional to the amount of wheat aleurone. Wheat aleurone and flour promoted the aggregation and flocculation of lipid droplets by increasing the viscosity. More importantly, the dietary fibers released from aleurone digestion can reduced the binding of lipase to lipid droplets by adsorbing lipid droplets to increase the steric hindrance effect. These results provide a better understanding of how whole grains affect lipid digestibility and will further contribute to the development of functional foods and the improvement of individual health.

Co-encapsulation of Paprika and Cinnamon Oleoresins by Spray Drying in a Mayonnaise Model: Bioaccessibility of Carotenoids Using in vitro Digestion.

This study aimed to investigate the digestibility and bioaccessibility of spray-dried microparticles co-encapsulating paprika and cinnamon oleoresins using simulated gastrointestinal conditions. It focused on exploring the potential of these co-encapsulated active compounds, which possess diverse technological and functional properties, particularly within a food matrix, in order to enhance their bioavailability. Mayonnaise was selected as the food matrix for its ability to promote the diffusion of carotenoids, as most hydrophobic compounds are better absorbed in the intestine when accompanied by digestible lipids. Model spice mayonnaise, containing 0.5 wt% paprika and cinnamon microparticles content, was formulated in compliance with Brazilian regulations for spices, seasonings, and sauce formulations. Droplet size distribution, optical microscopy and fluorescence microscopy analyses were conducted on the microparticles, model spice mayonnaise, and standard mayonnaise both before and after in vitro gastric and intestinal digestion. Following digestion, all samples demonstrated droplet aggregation and coalescence. Remarkably, dispersed particles (37.40 ± 2.58%) and model spice mayonnaise (17.76 ± 0.07%) showed the highest release rate of free fatty acids (FFAs), indicating efficient lipid digestion. The study found that using mayonnaise as a delivery system significantly increased bioaccessibility (22.7%). This suggests that particles in an aqueous medium have low solubility, while the high lipid composition of mayonnaise facilitates the delivery of active compounds from carotenoids present in paprika and cinnamon oleoresin after digestion.

Sucrose Esters and Beeswax Synergize to Improve the Stability and Viscoelasticity of Water-in-Oil Emulsions.

W/O emulsions are commonly used to prepare stable low-fat products, but their poor stability limits widespread applications. In this study, sucrose ester (SE) and beeswax were utilized to prepare an oil dispersion system in rapeseed oil, which was used as the external oil phase to further synergistically construct the W/O emulsion systems. The results show that spherical and fine crystals are formed under the synergistic effect of SE and BW (1.5 SE:0.5 BW). In this state, a dense interfacial crystal layer was easily formed, preventing droplet aggregation, leading to droplet size reduction (1-2 μm) and tight packing, improving viscoelasticity and resistance to deformation, and increasing the recovery rate (52.26%). The long-term stability of W/O emulsions containing up to 60 wt% water was found to be more than 30 days. The increase in the aqueous phase led to droplet aggregation, which increased the viscosity (from 400 Pa·s to 2500 Pa·s), improved the structural strength of the emulsion, and increased the width of the linear viscoelastic region (from 1% strain to 5% strain). These findings provide some technical support for the further development of stable low-fat products.

A Study on the Oil-Bearing Stability of Salt-Resistant Foam and an Explanation of the Viscoelastic Phenomenon

Foam is a medium-stable system composed of gas and liquid phases, which has the advantages of low density at the gas phase and high viscosity at the liquid phase, and has a wide application in oil and gas field development and mineral flotation, but its special medium-stable system also brings many problems in industry applications. Scientists have carried out extensive analyses and research on the foam stability and bubble-bursting mechanism, which initially clarified the rules of bubble breakage caused by environmental factors such as temperature and pressure, but the mechanism of bubble bursting under the action of internal factors such as liquid mineralization and oil concentration of the films is still not clearly defined. In this paper, we propose a compound salt-resistant foaming agent, investigated the influence of the aggregation and adsorption behavior of oil droplets on the liquid films and boundaries, and established a relevant aggregation and adsorption model with the population balance equation. We put forward a liquid film drainage mechanism based on the distribution, aggregation, and transport of oil droplets in the liquid films, so as to explain the changes in foam stability under the action of oil droplets. On the other hand, the viscoelastic analysis of foam fluid is performed with a rheometer, and the results show that in comparison with conventional power-law fluid, foam fluid has a complex rheological behavior for low shear thickening, but high shear thinning.

Construction of astaxanthin loaded Pickering emulsions gel stabilized by xanthan gum/lysozyme nanoparticles with konjac glucomannan from structure, protection and gastrointestinal digestion perspective

Pickering emulsion gels have demonstrated their efficacy in delivering bioactive compounds by effectively preventing droplet aggregation, Ostwald maturation, and phase separation through gel network. Astaxanthin (AST) Pickering emulsion gels stabilized by xanthan gum/lysozyme nanoparticles (XG/Ly NPs) and konjac glucomannan (KGM) were studied from rheological tests and textural analysis. The Pickering emulsion gel demonstrated the highest water holding capacity (WHC) at concentration of 2 % XG/Ly NPs, 60 % oil phase fraction, and 0.5 % KGM concentration. The presence of KGM was observed to enhance the plasticity of Pickering emulsion gels, as evidenced by the dense gel network structure formed on the surface of the droplets. Furthermore, the utilization of Pickering emulsion gels containing AST has demonstrated enhanced photostability and a protective effect on AST, as evidenced by antioxidant experiments. Moreover, the incorporation of KGM in Pickering emulsion gels has been found to reduce the release of free fatty acids (FFA) and the bioaccessibility of AST, as indicated in vitro digestion results. Overall, these findings indicate the potential of KGM-based Pickering emulsion gels as effective vehicles for the delivery of hydrophobic bioactive compounds within the food industry.

Evaluation of mung bean protein and aquafaba as co-stabilizer for sour aerated emulsions

The objective of this study was to investigate the impact of pH12 shifting treatment of protein and addition of a novel foam booster, aquafaba (AQ), on the properties of mung bean protein (MBP)-based sour whipped cream at pH 3.0. The characteristic interfacial adsorption of AQ–MBP, the effects of the emulsion and foam stabilizers on the freeze-thaw stability of the emulsions, and the whipping properties of emulsions were explored. The results showed that pH12-treated MBP (BMBP) emulsions exhibited significant aggregation of fat droplets due to the reduced ability of BMBP to absorb on the oil droplets compared to native MBP (NMBP). Despite having lower shear viscosity, the BMBP emulsion showed stronger foaming capacity but longer whipping time in subsequent aeration. Creep-recovery and shape retention tests indicated that whipped cream produced with BMBP exhibited lower hardness and was more difficult to stand, contrary to the overly firm texture of NMBP cream. The inclusion of AQ in the emulsion improved the stability and enhanced the trend of overrun during whipping. Combining NMBP and BMBP at a 1:1 ratio and incorporating AQ resulted in a freeze-thaw stable emulsion. It was determined that the optimum whipping time for this emulsion was 38 s longer than the commercially available product while the overrun exhibited a remarkable 19.9% increase.

Regulating the lipid droplet interface based on milk fat globule membrane and milk proteins to improve lipid digestion of model infant formula emulsion

The interfacial properties of lipid droplets play a crucial role in lipid digestion. In this study, milk fat globule membrane (MFGM) was used to improve the lipid droplet interface of model infant formula emulsions (IFEs). We focused on the effects of the addition sequence of MFGM and milk proteins commonly used in infant formula (IFE1: Milk proteins added before homogenization, MFGM added after homogenization; IFE2: MFGM added before homogenization, milk proteins added after homogenization; IFE3: MFGM and milk proteins added before homogenization) on lipid droplets' interfacial compositions, structure, and lipid digestion behaviors and compared with human milk (HM) and commercial infant formula (IF). The results showed that the interfacial protein load was significantly lower (P < 0.05), and the interfacial phospholipid load was significantly higher (P < 0.05) in IFE2 compared to IFE1, IFE3, and IF. The lipid droplet structure of IFE2 is closer to that of HM. MFGM fragments-covered lipid droplets can be observed in IFE2. In contrast, the lipid droplets in IFE1, IFE3, and IF were covered by casein micelles, and MFGM fragments were free in the serum phase. After digestion, the lipolysis degree of IFE2 (91.7 ± 1.51%) was comparable to that of HM (94.98 ± 1.08%) and significantly higher than other samples (P < 0.05). During digestion, IFE1 and IFE3 formed thicker and denser protein knit networks compared to IFE2. The lipid droplets in IFE1 and IFE3 were embedded in protein networks, thereby inhibiting lipid digestion. These results indicated that changes in the interfacial composition of lipid droplets improved lipid digestion by mitigating the aggregate and coalescence of protein and lipid droplets.

Lipid Deposition and Progesterone Synthesis Are Increased by miR-181b-5p through RAP1B/ERK1/2 Pathway in Chicken Granulosa Cells.

Steroid hormones secreted by granulosa cells are essential for maintaining normal development of chicken follicles. Our previous sequencing data indicated that miR-181b-5p and RAS-related protein 1B (RAP1B) appeared to function in chicken granulosa cells, which was further explored in this study. The results suggested that miR-181b-5p facilitated the aggregation of lipid droplets and the synthesis of progesterone. In contrast, RAP1B astricted lipid deposition and progesterone secretion. Cotransfection of the RAP1B overexpression vector with miR-181b-5p mimic eliminated the promoting effect of miR-181b-5p. Dual-luciferase reporter assay confirmed that miR-181b-5p bound directly to the 3' untranslated region (3' UTR) of RAP1B. We also found that miR-181b-5p and RAP1B reduced and enhanced the phosphorylation levels of extracellular signal-regulated kinases 1 and 2 (ERK1/2), respectively. The application of ERK1/2 activators and inhibitors demonstrated that ERK1/2 is a negative regulator of lipid deposition and progesterone synthesis. In conclusion, we revealed that miR-181b-5p accelerated lipid deposition and progesterone synthesis through the RAP1B/ERK1/2 pathway in chicken granulosa cells. miR-181b-5p and RAP1B may serve as new biomarkers in breeding to improve chicken reproductive performance and prevent ovary-related diseases.

An integrated simulation approach for demulsification of water-in-oil emulsions by medium coalescence

Medium coalescence, as a low energy consumption demulsification method, has been widely applied in many industries. During the water-in- oil emulsions flowing through medium bed, the dispersed water droplets not only collide and aggregate with each other, but also deposit and wet on the hydrophilic medium surface. Moreover, the formed large droplets may also breakup into small ones by the turbulent flow or the tiny fibers. Thus, an integrated approach is needed to predict the demulsification performance of water-in-oil (W/O) emulsion by medium coalescence. In this work, the population balance model (PBM) with considering Boltzmann motion and differential settlement was used to predict suspension droplets aggregation. The interaction between dispersed droplets and medium bed was calculated by a modified deposition model. Moreover, a published breakage model was selected to simulate the complex droplet breakage process. Then, the demulsification performance of W/O emulsion can be obtained by the variation of droplet size profile. To verify the integrated simulation approach, the existing experimental datasets were compared with the simulation results. After that, a sensitivity analysis was carried out to study parameters that affect the demulsification performance, such as flow velocity, capillary size, and continuous viscosity. The integrated approach proposed in this paper fills in the blank of the demulsification simulation of W/O emulsion by medium coalescence. It provides an in-depth understanding of the relationship between droplets behaviors and medium coalescence performance.

Controlling textural attributes of plant-based emulsions using heteroaggregation of cationic and anionic potato protein-coated oil droplets

There is a need for semi-solid food matrices constructed from plant-derived ingredients to formulate plant-based foods, like egg, cheese, meat, and mayonnaise analogs. This study showed that heteroaggregation could be used to create plant-based semi-solid matrices by blending cationic and anionic droplets together. Heteroaggregation was induced by mixing 10 wt% olive oil-in-water emulsions containing either cationic potato protein-coated oil droplets (PPI300E) or anionic potato protein-coated oil droplets (PPI200E). Extensive droplet aggregation occurred at intermediate mixing ratios (25–75 wt%) because of electrostatic attraction between the oppositely charged oil droplets. Heteroaggregation led to a large increase in shear viscosity and elastic modulus, which was attributed to the formation of a network of protein-coated oil droplets held together by electrostatic attraction. The highest viscosity and elastic modulus were observed in the emulsions containing 75 wt% PPI200E and 25 wt% PPI300E. When the mixed emulsions were heated from 25 to 90 °C and then cooled back to 25 °C, there were pronounced changes in their rheological properties. The shear modulus of the mixed emulsions tended to increase when they were heated above their thermal denaturation temperature, which was attributed to strengthening of hydrophobic attractions between the droplets. In contrast, the shear modulus tended to decrease steeply during cooling, which suggested that the network of aggregated oil droplets partially collapsed. Rearrangement and consolidation of the oil droplets in the particle network during storage led to gravitational separation. Our results show that semi-solid emulsified foods can be formed from plant-derived ingredients using relatively low concentrations of protein and oil using heteroaggregation. These emulsions may be useful as structuring agents in some plant-based foods.

High inner phase emulsion of fish oil stabilized with rutin-grass carp (Ctenopharyngodon idella) myofibrillar protein: Application as a fat substitute in surimi gel

This study investigated the effect of rutin-grass carp myofibrillar protein (R-GMP) co-stable fish oil high internal phase emulsion on the quality of surimi gel compared with the direct addition of soybean oil. Combined with the stability, microstructure and rheological properties, R-GMP (GMP: 3.0%, rutin: 12%,/GMP, w/w) could form a stable O/W type high internal phase Pickering emulsion with an oil-water ratio of 0.75. The L*, a*, and b* values and whiteness of silver carp surimi gel were increased significantly (P < 0.05) after fish oil-based high internal phase emulsion was added as oil. Meanwhile, compared with the direct addition of soybean oil, the hardness, chewiness, gel strength and water-holding capacity of surimi gel were significantly enhanced (P < 0.05) after the addition of R-GMP high internal phase emulsion, and more free water was bound to the gel network. The microstructure showed that the R-GMP high internal phase emulsion could be evenly distributed in the dense and ordered protein network gel in the form of small oil droplets, while the direct addition of soybean oil would produce an aggregation of oil droplets and destroy the network structure of the gel. In conclusion, R-GMP stabilized fish oil high internal phase emulsion optimizes the gel quality of oil-enhanced surimi gel, providing new ideas for healthy fat replacement and the development of functional emulsified surimi products.

The Chinese medicine Xin-tong-tai granule protects atherosclerosis by regulating oxidative stress through NOX/ROS/NF-κB signal pathway

BackgroundXin-tong-tai Granule (XTTG), a traditional Chinese medicine, has been used to treat atherosclerosis (AS), but its mechanism is poorly understood. Intriguingly, oxidative stress has been recognized as vital factors in the treatment of atherosclerosis. PurposeThis study aims to explore the potential mechanism of XTTG for treating AS. MethodsAn in-vivo model of AS was established by feeding ApoE-/- mice with a high-fat diet (HFD), and the Human Aortic Vascular Smooth Muscle Cells (HAVSMCs) were induced by oxidized low-density lipoprotein (ox-LDL) in vitro. After treatment, the blood lipid levels and pathological aortic changes of each group were observed, and the cell proliferation and lipid droplet aggregation in each group were evaluated. The oxidative stress indicators such as malondialdehyde (MDA) and superoxide dismutase (SOD) levels and related NOX/ROS/NF-κB signaling pathway indicators were observed. ResultsXTTG improved blood lipid levels and pathological aortic changes of ApoE−/− mice with HFD feeding, inhibited HAVSMCs proliferation and lipid droplet aggregation induced by ox-LDL, reduced MDA content, increased SOD content, inhibited NOX4 and p22phox protein expression, downregulated ROS content, inhibited IKK-α, IKK-β, NF-κB protein and mRNA expression and the phosphorylation of NF-κB. ConclusionXTTG can inhibit NOX/ROS/NF-κB signaling pathway, reduce damages caused by oxidative stress, and exert anti-AS effects.

Fabrication of carboxymethyl starch/xanthan gum combinations Pickering emulsion for protection and sustained release of pterostilbene

Carboxymethyl starch (CMS)/xanthan gum (XG) combinations with different ratios (CMS/XG: 1/1, 3/1, 5/1, 7/1, 9/1, w/w) were used as Pickering emulsion delivery systems to encapsulate pterostilbene (PTS) to improve its stability. The results showed that the Pickering emulsion prepared using CMS/XG combinations could effectively encapsulate PTS. When the mass ratio of CMS to XG was 1:1, the encapsulation efficiency reached 91.20 %. The spherical particles in the PTS emulsion were dissociated and homogenous. The results of backscattered light experiments and storage stability studies showed that the PTS emulsion system prepared using CMS/XG was uniform and stable, with no obvious phase separation or emulsion droplet coalescence. With an increase in the mass ratio of XG, the water distribution in the emulsion became more evenly distributed, and the aggregation of droplets was reduced. The PTS emulsion prepared using CMS/XG improved the storage retention percentage of PTS. The cumulative release of PTS in the simulated gastric fluid was significantly lower than that in simulated intestinal fluid. The Pickering emulsion prepared using CMS/XG combinations can be used as a delivery system for functional foods and help to develop an efficient and reliable release system for hydrophobic bioactive substances.

Modulating digestion by composite interfacial layer in structured oil-in-water emulsions

Oleogels were applied as the lipid phase in oil-in-water (O/W) emulsions as a strategy to modulate in vitro lipid digestion. Lipid phase was structured with fruit wax (FW) or FW combined with lecithin (phosphatidylcholine-rich fraction) (FWLEC), while emulsifiers with low (Tween 80- T80) or high (whey protein isolate- WPI) molecular weight emulsifiers were added in the aqueous phase. All emulsions showed comparable mean droplet size (1.2–1.5 µm). The combined effect of emulsifiers (T80 and WPI) and oleogelators (FW and LEC) influenced interfacial behavior, modifying the profile of surface pressure over time and interfacial elasticity (0.9–22.7 mN/m). After the simulation of gastric conditions, WPI emulsions yielded larger droplet sizes, lower absolute values of ζ-potential and extensive aggregation of droplets compared to T80-stabilized emulsions. On the other hand, intestinal lipolysis was highly influenced by the presence of oleogelators and emulsifiers forming the interface of the droplets (32.9–65.1% of free fatty acids released). Interestingly, emulsified FWLEC oleogels stabilized by WPI led to reduced lipolysis, showing the lowest rate and extent of free fatty acids released. This outcome shed light on designing mixed interfaces for lipid digestion control purposes.

Improving physical stability of pea protein-based emulsions near the isoelectric point via polysaccharide complexation

Development of plant protein-based mildly acidic beverages remains challenging as the pH range falls near the protein isoelectric point, destabilizing emulsions. To overcome this problem, it was hypothesized that complexation between plant proteins and polysaccharides could provide emulsion stability in this critical pH range. Four different polysaccharides (sugar beet pectin, gum Arabic (GA), guar gum, gellan gum) were mixed separately with pea protein isolate (PPI) in 1:1 ratio, and the critical pH values for the formation of soluble complexes were determined. Heating the mixture widened the optimal pH range for soluble complexation for pectin-PPI and GA-PPI below the isoelectric point, which was then used to prepare 5 wt% O/W emulsions with an aqueous phase containing 0.5 wt% biopolymers at pH 8.0 and pH 4.5. Emulsion stability was characterized using droplet size, charge, visual observation, microstructure, and accelerated gravitational separation. PPI-only emulsions were stable at pH 8.0 but extensively destabilized at pH 4.5. The GA-PPI emulsions showed high stability at pH 8.0; however, at pH 4.5, the soluble complexes failed to provide a stable emulsion due to extensive droplet aggregation and phase separation. The emulsion prepared with a co-soluble pectin-PPI mixture at pH 8.0 also showed droplet aggregation and phase separation. The most improved emulsion stability (smallest droplet size, no aggregation) was observed for the pectin-PPI soluble complex at pH 4.5. Findings from this study showed that soluble complexes could be obtained at the desired pH range depending on the polysaccharide sources, which can stabilize O/W emulsions even near the protein's isoelectric point.

Shear flow-driven droplet motion with smoothed dissipative particle dynamics

Droplet motion in shear flow is a typical phenomenon in nature that also plays an important role in the spread of COVID-19 when viruses like SARS-CoV-2 exist in exhalation droplets. In this paper, we adopted smoothed dissipative particle dynamics (SDPD) to simulate the Couette flow and Poiseuille flow. Then, the self-diffusion coefficient and the Schmidt number of the quiescent flow in SDPD are confirmed by comparison with those in DPD. In addition, the SDPD method with pacific coefficients is used to simulate the disintegration of droplets and the collisional aggregation and separation of droplets in shear flow. The applicability of the SDPD method is demonstrated through these simulations, which can be useful in the investigation of many complex fluid flows during the expansion of COVID-19.

Demulsification of o/w emulsion produced by polymer flooding injecting anionic polymeric surfactant

Anionic amphiphilic polymers (polymeric surfactant) have been applied in polymer flooding to improve its adaptability to reservoirs of low permeability, high salinity and high temperature. Some pilot and extended polymer flooding projects injecting anionic polymeric surfactants with interfacial activities produced very stable o/w emulsion, bringing about high oil carry-over in produced water which was very difficult to remove to meet re-injection specifications. Factors contributing to the stability of o/w emulsion produced by a polymer flooding project injecting an anionic amphiphilic polymer were investigated by means of phase separation test, interfacial tension and Zeta potential measurements, emulsion microscopic structure observation and determination, and identification of interfacial active species. Major mechanisms hindering the aggregation and coalescence of oil droplets in the stable o/w emulsion were identified as the electrostatic repulsion and steric repulsion exerted by the polymer coils attached to the surfaces of oil droplets. A novel combination of a nonionic block polyether SP-2002 and a low molecular weight anionic surfactant AS-2001was designed to effectively demulsify the stable o/w emulsion produced by the polymer flooding project. Field trial of SP-2002 and AS-2001, together with a chelating agent WS-2001, brought about much looser o/w emulsion and significantly reduced oil carry over in produced water separated by field 3-phase production separators and skim tanks. The average OIWs of produced water dropped from 790 ppm before the trial to 482 ppm during the second stage of the trial. OIW of the produced water at the end of the trial dropped from 426 ppm to 90 ppm after 24 h static settling at 35 °C and further reduced to 17 ppm after bench-top media filtration.