Formulation of food-grade microemulsions with glycerol monolaurate: effects of short-chain alcohols, polyols, salts and nonionic surfactants

Microfluidic nanobubbles: observations of a sudden contraction of microbubbles into nanobubbles

Microfluidic devices are often utilized to generate uniform-size microbubbles. In most microfluidic bubble generation experiments, once the bubbles are formed the gas inside the bubbles begin to dissolve into the surrounding aqueous environment. The bubbles shrink until they attain an equilibrium size dictated by the concentration and type of amphiphilic molecules stabilizing the gas-liquid interface. Here, we exploit this shrinkage mechanism, and control the solution lipid concentration and microfluidic geometry, to make monodisperse bulk nanobubbles. Interestingly, we make the surprising observation of a critical microbubble diameter above and below which the scale of bubble shrinkage dramatically changes. Namely, microbubbles generated with an initial diameter larger than the critical diameter shrinks to a stable diameter that is consistent with previous literature. However, microbubbles that are initially smaller than the critical diameter experience a sudden contraction into nanobubbles whose size is at least an order-of-magnitude below expectations. We apply electron microscopy and resonance mass measurement methods to quantify the size and uniformity of the nanobubbles, and probe the dependence of the critical bubble diameter on the lipid concentration. We anticipate that further analysis of this unexpected microbubble sudden contraction regime can lead to more robust technologies for making monodisperse nanobubbles.

In Vitro and In Vivo Functional Viability, and Biocompatibility Evaluation of Bovine Serum Albumin-Ingrained Microemulsion: A Model Based on Sesame Oil as the Payload for Developing an Efficient Drug Delivery Platform

Combination of bovine serum albumin with microemulsions as constituting ingredient biopolymer has long been regarded an innovative method to address the surface functionalization and stability issues in the targeted payload deliveries, thereupon producing effectively modified microemulsions, which are superior in loading capacity, transitional and shelf-stability, as well as site-directed/site-preferred delivery, has become a favored option. The current study aimed to develop an efficient, suitable and functional microemulsion system encapsulating sesame oil (SO) as a model payload towards developing an efficient delivery platform. UV-VIS, FT-IR, and FE-SEM were used to characterize, and analyze the developed carrier. Physicochemical properties assessments of the microemulsion by dynamic light scattering size distributions, zeta-potential, and electron micrographic analyses were performed. The mechanical properties for rheological behavior were also studied. The HFF-2 cell line and hemolysis assays were conducted to ascertain the cell viability, and in vitro biocompatibility. The in vivo toxicity was determined based on a predicted median lethal dose (LD₅₀) model, wherein the liver enzymes' functions were also tested to assess and confirm the predicted toxicity.

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

Falling film evaporation processes involve high fluid velocities with continuous variations in local film thickness, fluid composition, and viscosity. This contribution presents a parallel and complementary film thickness and concentration mapping distribution in falling films using a non-invasive fluorescence and near-infrared imaging technique. The experiments were performed with a mixture of glycerol/water with a mass fraction from 0 to 0.65 gglycgtotal-1 and operating ranges similar to evaporation processes. The measurement system was designed by integrating two optical measurement methods for experimental image analysis. The film thickness was evaluated using a VIS camera and high-power LEDs at 470 nm. The local glycerol concentration gglycgtotal-1 was determined using a NIR camera and high-power LEDs at 1050, 1300, 1450 and 1550 nm. A multiwavelength analysis with all NIR wavelengths was implemented with a better correlation for falling films at low flow velocity. The results show an improvement in the analysis of falling films with high flow velocities up to almost 500 mm/s by using only the 1450 nm wavelength and the fluorescence measurement. Simultaneous imaging analysis of film thickness and concentration in falling films provides further insight into understanding mass and heat transport and thus supports the optimization of falling film evaporators.

Formation of sacha inchi oil microemulsion systems: effects of non-ionic surfactants, short-chain alcohols, straight-chain esters and essential oils

BACKGROUND

This study reports the formation of sacha inchi oil (SIO) microemulsions for food and cosmetic applications. Effects of non-ionic surfactants, short-chain alcohols, essential oil and straight-chain esters on the phase behavior and formulation of U-type microemulsion were investigated. Pseudo ternary phase diagrams were constructed to assess the influence of these factors using water titration method. Structural transitions were measured along several water dilution lines using conductivity and viscosity tools.

RESULTS

Among four different surfactants, Tween 80 solubilized the maximum oil and induced the formation of a U-type microemulsion system. Oil solubilization was decreased in the presence of short-chain alcohols. In addition, the system containing straight-chain esters as the cosolvent showed a higher expansion effect in the U-type areas than that containing essential oils. Finally, upon water dilution of three systems with SIO/ethyl acetate of 1:1, 1:2 and 1:3, microstructural transition from W/O to bicontinuous occurred at 200 g kg^-1 (w/w) water content, and then to O/W structure at 650 g kg^-1 (w/w) water content.

CONCLUSION

Straight-chain esters as cosolvent is a potential strategy to extend the dilutability of SIO microemulsions. © 2021 Society of Chemical Industry.

Effect of cellulose and starch fatty acid esters addition on microstructure and physical properties of arabinoxylan films

Arabinoxylan (AX) and cellulose were extracted from wheat straw, whereas starch was extracted from potato peel. Thereafter, cellulose and starch were esterified with lauric, myristic, palmitic and stearic acids to prepare corresponding cellulose (CFAs) and starch fatty acid esters (SFAs) with DS 2.1-2.8. XRD study revealed remarkable loss of crystallinity in cellulose and starch due to fatty acid esterification. The addition of palmitate and stearate esters of cellulose and starch to AX formed laminar film microstructures which limited water vapor permeability whereas films prepared by blending AX with laurate and myristate esters of starch and cellulose were less effective as water vapor barrier due to their non-layer microstructures. The laminar structures also resulted significant reduction in mechanical strength of the composite films. Furthermore, all AX-CFAs and AX-SFAs films were thermally more stable than native composite films. These films might be used to produce industrially useful coating material for food products.

Modulation of the Gut Microbiota during High-Dose Glycerol Monolaurate-Mediated Amelioration of Obesity in Mice Fed a High-Fat Diet

Obesity and associated metabolic disorders are worldwide public health issues. The gut microbiota plays a key role in the pathophysiology of diet-induced obesity. Glycerol monolaurate (GML) is a widely consumed food emulsifier with antibacterial properties. Here, we explore the anti-obesity effect of GML (1,600 mg/kg of body weight) in high-fat diet (HFD)-fed mice. HFD-fed mice were treated with 1,600 mg/kg GML. Integrated microbiome, metabolome, and transcriptome analyses were used to systematically investigate the metabolic effects of GML, and antibiotic treatment was used to assess the effects of GML on the gut microbiota.

Obesity and associated metabolic disorders are worldwide public health issues. The gut microbiota plays a key role in the pathophysiology of diet-induced obesity. Glycerol monolaurate (GML) is a widely consumed food emulsifier with antibacterial properties. Here, we explore the anti-obesity effect of GML (1,600 mg/kg of body weight) in high-fat diet (HFD)-fed mice. HFD-fed mice were treated with 1,600 mg/kg GML. Integrated microbiome, metabolome, and transcriptome analyses were used to systematically investigate the metabolic effects of GML, and antibiotic treatment was used to assess the effects of GML on the gut microbiota. Our data indicated that GML significantly reduced body weight and visceral fat deposition, improved hyperlipidemia and hepatic lipid metabolism, and ameliorated glucose homeostasis and inflammation in HFD-fed mice. Importantly, GML modulated HFD-induced gut microbiota dysbiosis and selectively increased the abundance of Bifidobacterium pseudolongum. Antibiotic treatment abolished all the GML-mediated metabolic improvements. A multiomics (microbiome, metabolome, and transcriptome) association study showed that GML significantly modulated glycerophospholipid metabolism, and the abundance of Bifidobacterium pseudolongum strongly correlated with the metabolites and genes that participated in glycerophospholipid metabolism. Our results indicated that GML may be provided for obesity prevention by targeting the gut microbiota and regulating glycerophospholipid metabolism.

New Force Field Model for Propylene Glycol: Insight to Local Structure and Dynamics

In this work we developed a new force field model (FFM) for propylene glycol (PG) based on the OPLS all-atom potential. The OPLS potential was refined using quantum chemical calculations, taking into account the densities and self-diffusion coefficients. The validation of this new FFM was carried out based on a wide range of physicochemical properties, such as density, enthalpy of vaporization, self-diffusion coefficients, isothermal compressibility, surface tension, and shear viscosity. The molecular dynamics (MD) simulations were performed over a large range of temperatures (293.15-373.15 K). The comparison with other force field models, such as OPLS, CHARMM27, and GAFF, revealed a large improvement of the results, allowing a better agreement with experimental data. Specific structural properties (radial distribution functions, hydrogen bonding and spatial distribution functions) were then analyzed in order to support the adequacy of the proposed FFM. Pure propylene glycol forms a continuous phase, displaying no microstructures. It is shown that the developed FFM gives rise to suitable results not only for pure propylene glycol but also for mixtures by testing its behavior for a 50 mol % aqueous propylene glycol solution. Furthermore, it is demonstrated that the addition of water to the PG phase produces a homogeneous solution and that the hydration interactions prevail over the propylene glycol self-association interactions.

Microemulsion formulation of Carbendazim and its in vitro antifungal activities evaluation

The fungus Rhizoctonia solani Kuhn is a widespread and destructive plant pathogen with a very broad host range. Although various pathogens, including R. solani, have been traditionally controlled using chemical pesticides, their use faces drawbacks such as environmental pollution, development of pesticide resistance, and other negative effects. Carbendazim is a well-known antifungal agent capable of controlling a broad range of plant diseases, but its use is hampered by its poor aqueous solubility. In this study, we describe an environmentally friendly pharmaceutical microemulsion system using carbendazim as the active ingredient, chloroform and acetic acid as solvents, and the surfactants HSH and 0204 as emulsifiers. This system increased the solubility of carbendazim to 30 g/L. The optimal microemulsion formulation was determined based on a pseudo-ternary phase diagram; its physicochemical characteristics were also tested. The cloud point was greater than 90°C and it was resistant to freezing down to −18°C, both of which are improvements over the temperature range in which pure carbendazim can be used. This microemulsion meets the standard for pesticide microemulsions and demonstrated better activity against R. solani AG1-IA, relative to an aqueous solution of pure carbendazim (0.2 g/L). The mechanism of activity was reflected in the inhibition of against R. solani AG1-IA including mycelium growth, and sclerotia formation and germination were significantly better than that of 0.2 g/L carbendazim water solution according to the results of t-test done by SPSS 19.

Effects of propylene glycol alginate and sucrose esters on the physicochemical properties of modified starch-stabilized beverage emulsions

This study was conducted to investigate the effect of main emulsion components namely, modified starch, propylene glycol alginate (PGA), sucrose laurate and sucrose stearate on creaming index, cloudiness, average droplet size and conductivity of soursop beverage emulsions. Generally, the use of different emulsifiers or a mixture of emulsifiers has a significant (p < 0.05) effect on the response variables studied. The addition of PGA had a significant (p < 0.05) effect on the creaming index at 55 °C, while PGA-stabilized (PGA1) emulsions showed low creaming stability at both 25 °C and 55 °C. Conversely, the utilization of PGA either as a mixture or sole emulsifier, showed significantly (p < 0.05) higher cloudiness, as larger average droplet size will affect the refractive index of the oil and aqueous phases. Additionally, the cloudiness was directly proportional to the mean droplet size of the dispersed phase. The inclusion of PGA into the formulation could have disrupted the properties of the interfacial film, thus resulting in larger droplet size. While unadsorbed ionized PGA could have contributed to higher conductivity of emulsions prepared at low pH. Generally, emulsions prepared using sucrose monoesters or as a mixture with modified starch emulsions have significantly (p < 0.05) lower creaming index and conductivity values, but higher cloudiness and average droplet size.

Microemulsions with Mixed Nonionic Surfactants and Isopropylmyristate

Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropylmyristate microemulsion systems were formulated and investigated using electrical conductivity and small angle X-ray scattering. The solubilization capacity of water in oil is dependent on the surfactants mixing ratio (w/w). The free energy of solubilization (ΔGo s) values for water-in-oil microemulsions were calculated and found to decrease with water content in the water-in-oil microemulsions, they decreased with increasing ethoxylated mono-di-glyceride content in the mixed surfactants. The activation energy of conductive flow was estimated and a percolation phenomenon was revealed in these systems. Small angle X-ray scattering results indicate that the periodicity increases linearly with the increase in the water volume fraction in these microemulsions. The correlation length increases with the increase in the water volume fraction to a certain value then decreases.

In vitro and in vivo antifungal activity of a water-dilutable cassia oil microemulsion against Geotrichum citri-aurantii

BACKGROUND

Recently, food-grade microemulsions have been of increasing interest to researchers and have shown great potential in industrial applications. In this study a food-grade water-dilutable microemulsion system with cassia oil as oil, ethanol as cosurfactant, Tween 20 as surfactant and water was developed and its antifungal activity in vitro and in vivo against Geotrichum citri-aurantii was assessed.

RESULTS

The phase diagram results confirmed the feasibility of forming a water-dilutable microemulsion based on cassia oil. One microemulsion formulation, cassia oil/ethanol/Tween 20 = 1:3:6 (w/w/w), was selected with the capability to undergo full dilution with water. The average particle size was 6.3 nm. The in vitro antifungal experiments showed that the microemulsion inhibited fungal growth on solid medium and prevented arthroconidium germination in liquid medium and that cassia oil had stronger activity when encapsulated in the microemulsion. The in vivo antifungal experiments indicated that the water-dilutable microemulsion was effective in preventing postharvest diseases of citrus fruits caused by G. citri-aurantii.

CONCLUSION

The results of this study suggest a promising utilisation of water-dilutable microemulsions based on essential oils for the control of postharvest diseases.

Characterization and antimicrobial activity of a pharmaceutical microemulsion

The characterization of a pharmaceutical microemulsion system with glycerol monolaurate as oil, ethanol as cosurfactant, Tween 40 as surfactant, sodium diacetate and water, and the antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Aspergillus niger and Penicillium expansum have been studied. The influence of ethanol and sodium diacetate on oil solubilization capability was clearly reflected in the phase behavior of these systems. One microemulsion formulation was obtained and remained stable by physical stability studies. The antimicrobial assay using solid medium diffusion method showed that the prepared microemulsion was comparable to the commonly used antimicrobials as positive controls. The kinetics of killing experiments demonstrated that the microemulsion caused a complete loss of viability of bacterial cells (E. coli, S. aureus and B. subtilis) in 1 min, killed over 99% A. niger and P. expansum spores and 99.9% C. albicans cells rapidly within 2 min and resulted in a complete loss of fungal viability in 5 min. The fast killing kinetics of the microemulsion was in good agreement with the transmission electron microscopy observations, indicating the antimembrane activity of the microemulsion on bacterial and fungal cells due to the disruption and dysfunction of biological membranes and cell walls.

Antifungal activity of a food-grade dilution-stable microemulsion against Aspergillus niger

AIMS

To study the antifungal activities of a prepared food-grade dilution-stable microemulsion against Aspergillus niger.

METHODS AND RESULTS

Results from the antifungal activity on solid medium by agar dilution method showed that the microemulsion caused complete growth inhibition at 2000 ppm, and at 1000 ppm, showed 55% growth inhibition after 4 days of incubation and a delay of conidiation by 1 day compared with controls. Results from the antifungal activity in liquid medium by broth dilution method showed that the growth of A. niger was completely inhibited when a liquid medium containing 10(6) spores per ml was treated with 500 ppm of microemulsion, which was determined by minimum fungicidal concentration. Study of fungicidal kinetics showed that more than 99% of viable spores were killed within 15 min. These antifungal activities were confirmed by scanning electron microscopy, light microscopy and increased Ca(+2), K(+) and Mg(+2) leakages.

CONCLUSIONS

The results suggest that the prepared microemulsions are effective antifungal systems with excellent growth inhibition and sporicidal activities, and indicate that their antifungal activity may be to the result of the disruption and dysfunction of A. niger cell walls and biological membranes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests the potential use of food-grade dilution-stable microemulsions for antifungal use in the food and pharmaceutical industries.