Thyme oil nanoemulsions coemulsified by sodium caseinate and lecithin

Enhancing bioactivity of Callistemon citrinus (Curtis) essential oil through novel nanoemulsion formulation

The main focus of this study was to create a stable and efficient nanoemulsion (NE) using Callistemon citrinus essential oil (EO). Various factors affecting the NE's stability were optimized including oil %, Tween 80%, time of sonication, and its accelerated stability was examined. The research also considered the antibacterial, antifungal, and larvicidal effects of the optimized NE (B10). The optimum NE stood out for its stability, featuring a particle size of 33.15 ± 0.32 nm. Analysis via IR spectroscopy confirmed successful EO encapsulation in B10. The formulation remained stable for six months, with B10 showing significantly higher antibacterial and antifungal potency compared to the pure oil. When samples were subjected to tests against Fusarium oxysporum, B10 exhibited a MIC value of 62.5 mg/mL, whereas the pure oil showed a MIC value of 250 mg/mL. This indicates that the B10 formulation was 50 times more effective than the EO. In terms of antibacterial activity against Escherichia coli, the MIC value was 0.256 mg/mL for B10 and 4 mg/mL for the EO. Also, pure oil and B10 displayed larvicidal effects against Chilo suppressalis (Walker) larvae, with B10 eliminating 95.2% of larvae in 48 h. Overall, stable and optimum C. citrinus NE with its strong antimicrobial qualities, shows promise as an effective fungicide and insecticide.

Physical, morphological and storage stability of clove oil nanoemulsion based delivery system

Clove oil based Nanoemulsions (NE) were prepared ultrasonically using Tween 80 and soy lecithin as synthetic and natural surfactants, respectively. The developed NEs were characterized for various parameters (particle size, polydispersity index, zeta potential, morphology, viscosity, colour, turbidity and pH) and the comparative effect of both the surfactants at variable levels (oil:tween 80-1:1, 1:2, 1:3 and 1:4 and oil: soy lecithin- 1:1, 1:1.5 and 1:2) was assessed. It was found that the type of surfactant and oil to surfactant ratio significantly affected particle size and stability of NEs. The NE prepared using tween 80 @1:3 had smallest average droplet diameter (40.9 nm). The formulated NEs were stored at 25 °C and 4 °C and analyzed for turbidity, pH and phase separation up to 90 days. Results revealed that the type and concentration of the surfactant significantly influenced the particle size and stability of NEs. NEs prepared using tween 80 were found to be more viscous than those prepared with soy lecithin. The prepared clove oil NEs have important implication to be used as a natural delivery system to increase the shelf life of food products.

Physico-chemical characterization of ultrasound assisted clove oil-loaded nanoemulsion: As enhanced antimicrobial potential

Clove oil has a high eugenol content, making it an effective antimicrobial essential oil; nevertheless, its low water solubility, high volatility, and organoleptic qualities limit its use in food systems. As a result, we created an antibacterial system using clove oil-in-water nanoemulsion. Clove oil nanoemulsions were produced using whey protein concentrate (0.1-1%) as an emulsifier by ultrasonication and various physico-chemical characteristics (stability, particle size, zeta-potential, and poly dispersity index) were investigated. Mean particle size, zeta potential and polydispersity index of the most stable nanoemulsion were 279.0 ± 8.43 nm, -34.5 ± 0.12 mV, and 0.179 ± 0.012, respectively. Most stable nanoemulsion was fairly stable at different processing parameters such as various pH (3.0 - 7.0), temperature ranges (63 - 121 °C), and ionic strengths (0.1 - 1.0 M NaCl). Finally, antimicrobial activities, such as minimum inhibitory concentration was found with 50 µL, whereas minimum bactericidal concentration was observed to be 90 µL after 8 h contact time, against E. coli and B. subtilis strains.

Effect of microcrystalline cellulose under different hydrolysis durations on the stability of thyme oil emulsion

The thyme oil emulsion was prepared using a novel type of nanocellulose obtained under different hydrolysis durations. The effect of different cellulose structures on interfacial adsorption properties of emulsion and loading efficiency of thyme oil were analyzed. The results showed that the cellulose particles became more homogeneous and hydrophilic after hydrolysis duration for 10 h. The loading efficiency of thyme oil for all emulsions reached about 80%. The retention rate of thyme oil decreased during the storage period, and rising temperatures will exacerbate the loss of thyme oil. Compared to Hd2, emulsions stabilized by Hd10 exhibited better stability and higher retention at all storage conditions. Cellulose emulsion can increase the dispersion and improve the stability of thyme oil. A smaller cellulose particle could make the emulsion become more stable. The experimental results confirmed that cellulose can be used as a stabilizer to encapsulate and transport hydrophobic active ingredient. PRACTICAL APPLICATION: The study results demonstrated that the emulsion transport system was developed using cellulose nanoparticles prepared by hydrolysis. The system can be used to load hydrophobic active substances (active peptides, curcumin, β-carotene, essential oils, etc.). It can protect the active substance from environmental damage, enhance water solubility and stability, and improve the bioavailability of the active substance.

The physicochemical properties and stability of flaxseed oil emulsions: effects of emulsification methods and the ratio of soybean protein isolate to soy lecithin

BACKGROUND

The properties and stability of emulsion rely greatly on the emulsification method and emulsifier. In this study, different emulsification methods (high-speed homogenization, ultrasonic treatment and their combination) were employed for the preparation of emulsions stabilized by soybean protein isolate (SPI) and soy lecithin (SLT) at three ratios. The microstructure, hydrodynamic average diameter, ζ-potential, creaming stability and low-field nuclear magnetic resonance relaxation behaviors of emulsions were investigated.

RESULTS

The results indicated that the influence of emulsification method was closely related to the ratio of SPI/SLT. Overall, the SPI-SLT-stabilized emulsion treated by ultrasound showed better stability and uniformity, while the combined treatment of high-speed homogenization and ultrasound was helpful in improving the uniformity and stability of SPI-stabilized Pickering emulsion. However, the SLT-stabilized emulsions all exhibited worse uniformity in terms of particle size distribution and polydispersity index.

CONCLUSION

These results will be helpful for selecting an appropriate emulsification method and emulsifier to improve the stability of emulsions. © 2021 Society of Chemical Industry.

Development of a High Internal Phase Emulsion of Antarctic Krill Oil Diluted by Soybean Oil Using Casein as a Co-Emulsifier

Antarctic krill oil (AKO) with 5–30% (w/w) dilution by soybean oil was co-emulsified by phospholipids (PLs) naturally present in AKO and 2% (w/w) casein in the aqueous phase to prepare high internal phase emulsions (HIPEs). The results showed that raising the AKO level resulted in concave-up changes in the mean size of oil droplets which became more densely packed. Confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (cryo-SEM) micrographs revealed that PLs at higher concentrations expelled more casein particles from the oil droplet surface, which facilitated the formation of a crosslinked network structure of HIPEs, leading to reduced mobility of water molecules, extended physical stability, and somewhat solid-like behavior. The rheological analysis showed at lower levels of AKO promoted fluidity of emulsions, while at higher levels it increased elasticity. Lastly, increasing the AKO level slowed down the oxidation of HIPEs. These findings provide useful insights for developing HIPEs of highly viscous AKO and its application in foods.

An overview of nanoemulsion characterization via atomic force microscopy

Nanoemulsion-based systems are widely applied in food industries for protecting active ingredients against oxidation and degradation and controlling the release rate of active core ingredients under particular conditions. Visualizing the interface morphology and measuring the interfacial interaction forces of nanoemulsion droplets are essential to tailor and design intelligent nanoemulsion-based systems. Atomic force microscopy (AFM) is being established as an important technique for interface characterization, due to its unique advantages over traditional imaging and surface force-determining approaches. However, there is a gap in knowledge about the applicability of AFM in characterizing the droplet interface properties of nanoemulsions. This review aims to describe the fundamentals of the AFM technique and nanoemulsions, mainly focusing on the recent use of AFM to investigate nanoemulsion properties. In addition, by reviewing interfacial studies on emulsions in general, perspectives for the further development of AFM to study nanoemulsions are also discussed.

Design of biopolymer carriers enriched with natural emulsifiers for improved controlled release of thyme essential oil

This work aims to characterize a novel system for thyme essential oil delivery based on the combination of natural emulsifiers (soy protein and soy lecithin) and alginate, produced using the extrusion technique. The formulations are optimized concerning alginate and soy protein concentrations (both 1 to 1.5 wt.%), and consequently lecithin amount, in order to achieve spherical beads in the range 2.0 to 2.3 mm and 1.2 to 1.4 mm, wet and dry, respectively. Fourier-transform infrared analysis was performed, proving that there are interactions between all components. Lecithin-soy protein synergistic combination improved entrapment efficiency of total polyphenols (for nearly 12%) and decreased thymol release in a simulated gastric solution for nearly 35%, in comparison with beads without lecithin. The addition of lecithin enhances the thermal properties of the polysaccharide-protein systems at 50 °C after 3 hr of heating. The mechanical stability of the biopolymer carriers is improved with lecithin addition and the elastic modulus varied from 80.06 to 123.7 kPa, depending on the formulation. Alginate/soy protein/lecithin are effective carriers for the encapsulation, protection, and controlled release of thyme essential oil. PRACTICAL APPLICATION: There is unfortunately growing human resistance to antibiotics. This work offers a novel system for effective protection and controlled release of thyme essential oil in the small intestine. The mechanical and thermal properties of the carrier were estimated as they indicate how the beads will be able to resist stress during their incorporation into food (i.e. cookies-mixing, baking). The proposed approach offers ''green advantage'' as arises from all-natural materials.

Physicochemical and emulsifying properties of mussel water-soluble proteins as affected by lecithin concentration

The effects of lecithin addition at different concentrations (0-2.0%) on the physicochemical and emulsifying properties of mussel water-soluble proteins (MWP) were investigated. In solution system, low lecithin concentration (0.5%-1.0%) induced the aggregation and increased turbidity of composite particles. Lecithin addition caused changes in secondary structure and induced partial unfolding of MWP. Hydrophobic interactions between MWP and lecithin may contribute to the exposure of chromophores and hydrophobic groups of MWP. The interfacial tension decreased with lecithin addition. However, at a high lecithin concentration (1.5%-2.0%), the degree of aggregation and state of unfolding alleviated due to competitive adsorption. In emulsion system, with the low concentration of lecithin addition (0.5%-1.0%), droplet size and surface charge of emulsion decreased. The emulsion activity index, emulsion stability index, percentage of adsorbed protein increased. Both creaming stability and viscoelastic properties improved. At an intermediate lecithin concentration (1.0%), the emulsion showed the highest physical stability, while further addition of lecithin caused a slight deterioration in emulsifying properties. Overall, these results indicated the possibility that the lecithin-MWP mixed emulsifiers can be used to obtain emulsions with desirable properties.

Encapsulation of Vitamins A and E as Spray-Dried Additives for the Feed Industry

Encapsulated fat-soluble powders containing vitamin A (VA) and E (VE) were prepared as a feasible additive for extruded feed products. The effect of the encapsulating agents (Capsul-CAP®, sodium caseinate-SC) in combination with Tween 80 (TW) as an emulsifier and maltodextrin (MD) as a wall material on the physicochemical properties of emulsions and powders was evaluated. First, nanoemulsions containing MD:CAP:TW:VA/VE and MD:SC:TW:VA/VE were prepared and characterized. Then, powders were obtained by means of spray-drying and analyzed in terms of the product yield, encapsulation efficiency, moisture content, porosity, surface morphology, chemical structure, and thermal properties and thermo-oxidative/thermal stability. Results showed that although nanoemulsions were obtained for all the compositions, homogeneous microcapsules were found after the drying process. High product yield and encapsulation efficiency were obtained, and the presence of the vitamins was corroborated. The characteristics of the powders were mainly influenced by the encapsulating agent used and also by the type of vitamin. In general, the microcapsules remained thermally stable up to 170 °C and, therefore, the proposed encapsulation systems for vitamins A and E were suitable for the preparation of additives for the feed manufacturing through the extrusion process.

An Overview of Micro- and Nanoemulsions as Vehicles for Essential Oils: Formulation, Preparation and Stability

The interest around essential oils is constantly increasing thanks to their biological properties exploitable in several fields, from pharmaceuticals to food and agriculture. However, their widespread use and marketing are still restricted due to their poor physico-chemical properties; i.e., high volatility, thermal decomposition, low water solubility, and stability issues. At the moment, the most suitable approach to overcome such limitations is based on the development of proper formulation strategies. One of the approaches suggested to achieve this goal is the so-called encapsulation process through the preparation of aqueous nano-dispersions. Among them, micro- and nanoemulsions are the most studied thanks to the ease of formulation, handling and to their manufacturing costs. In this direction, this review intends to offer an overview of the formulation, preparation and stability parameters of micro- and nanoemulsions. Specifically, recent literature has been examined in order to define the most common practices adopted (materials and fabrication methods), highlighting their suitability and effectiveness. Finally, relevant points related to formulations, such as optimization, characterization, stability and safety, not deeply studied or clarified yet, were discussed.

Pharmaceutical applications of chitosan

Chitosan (CS) is a linear polysaccharide which is achieved by deacetylation of chitin, which is the second most plentiful compound in nature, after cellulose. It is a linear copolymer of β-(1 → 4)-linked 2-acetamido-2-deoxy-β-d-glucopyranose and 2-amino-2-deoxy-β-d-glucopyranose. It has appreciated properties such as biocompatibility, biodegradability, hydrophilicity, nontoxicity, high bioavailability, simplicity of modification, favorable permselectivity of water, outstanding chemical resistance, capability to form films, gels, nanoparticles, microparticles and beads as well as affinity to metals, proteins and dyes. Also, the biodegradable CS is broken down in the human body to safe compounds (amino sugars) which are easily absorbed. At present, CS and its derivatives are broadly investigated in numerous pharmaceutical and medical applications including drug/gene delivery, wound dressings, implants, contact lenses, tissue engineering and cell encapsulation. Besides, CS has several OH and NH₂ functional groups which allow protein binding. CS with a deacetylation degree of ~50% is soluble in aqueous acidic environment. While CS is dissolved in acidic medium, its amino groups in the polymeric chains are protonated and it becomes cationic which allows its strong interaction with different kinds of molecules. It is believed that this positive charge is responsible for the antimicrobial activity of CS through the interaction with the negatively charged cell membranes of microorganisms. This review presents properties and numerous applications of chitosan-based compounds in drug delivery, gene delivery, cell encapsulation, protein binding, tissue engineering, preparation of implants and contact lenses, wound healing, bioimaging, antimicrobial food additives, antibacterial food packaging materials and antibacterial textiles. Moreover, some recent molecular dynamics simulations accomplished on the pharmaceutical applications of chitosan were presented.

Physical and oxidative stability of high fat fish oil-in-water emulsions stabilized with sodium caseinate and phosphatidylcholine as emulsifiers

The physical and oxidative stability of high-fat omega-3 delivery systems such as fish oil-in-water emulsions stabilized with combinations of sodium caseinate (CAS) and phosphatidylcholine (PC) was optimized. The influence of fish oil content (50, 60 and 70%, w/w), amount of total emulsifier CAS + PC (1.4, 2.1 and 2.8%, w/w) and ratio between CAS and PC (0.4, 1.2 and 2) on physical and oxidative parameters was investigated. Creaming and droplet size significantly decreased when the amount of fish oil, total emulsifier and ratio of CAS to PC were increased. Viscosity decreased significantly with decreasing fish oil content, whereas the ratio of CAS to PC did not have a significant influence. Decreasing the ratio of CAS to PC led to emulsions with a significantly lower concentration of 1-penten-3-ol, while no significant effect was found for other volatiles such as (E)-2-pentenal, (E)-2-hexenal and (E,E)-2,4-heptadienal.

Nanoemulsions stabilized by non-ionic surfactants: stability and degradation mechanisms

The prevailing opinion in the literature is that the main mechanism of O/W nanoemulsion degradation is Ostwald ripening. Nevertheless, the experimental rates of Ostwald ripening are usually several orders of magnitude higher than the theoretical values. This suggests that other mechanisms, such as coalescence, flocculation and subsequent creaming, significantly influence nanoemulsion breakdown. We investigated O/W nanoemulsions stabilized by Brij 30 or by a mixture of Tween 80 and Span 80 and with liquid paraffin as a dispersed phase. The results indicate that Ostwald ripening is the main process leading to nanoemulsion coarsening only in nanoemulsions with low oil phase fractions of up to 0.05. For quasi-steady state conditions the rates of Ostwald ripening are equal to (1.5 ± 0.3) × 10-29 and (1.1 ± 0.3) × 10-29 m3 s-1 in nanoemulsions with Brij 30 and Tween 80 & Span 80, respectively. In nanoemulsions with oil phase fractions of 0.15-0.45, different mechanisms are identified. Flocculation prevails over other processes during the first days in nanoemulsions stabilized by Brij 30. Coalescence is the main mechanism of nanoemulsion degradation for long times. An increase in droplet size 5-10 days after nanoemulsion preparation due to Ostwald ripening takes place in the case of nanoemulsion stabilization by Tween 80 and Span 80. The stability behavior of these nanoemulsions at later stages is distinctly affected by coalescence and flocculation.

Improving emulsion formation, stability and performance using mixed emulsifiers: A review

The formation, stability, and performance of oil-in-water emulsions may be improved by using combinations of two or more different emulsifiers, rather than an individual type. This article provides a review of the physicochemical basis for the ability of mixed emulsifiers to enhance emulsion properties. Initially, an overview of the most important physicochemical properties of emulsifiers is given, and then the nature of emulsifier interactions in solution and at interfaces is discussed. The impact of using mixed emulsifiers on the formation and stability of emulsions is then reviewed. Finally, the impact of using mixed emulsifiers on the functional performance of emulsifiers is given, including gastrointestinal fate, oxidative stability, antimicrobial activity, and release characteristics. This information should facilitate the selection of combinations of emulsifiers that will have improved performance in emulsion-based products.

Optimization of cinnamon oil nanoemulsions using phase inversion temperature method: Impact of oil phase composition and surfactant concentration

Essential oils, such as those isolated from cinnamon, are effective natural antimicrobial agents, but their utilization is limited by their low water-solubility. In this study, phase inversion temperature (PIT) was used to prepare cinnamon oil nanoemulsions. To this aim, it was hypothesized that cinnamon oil nanoemulsions could be fabricated by optimizing the oil phase composition and surfactant concentration of the system and their stability could be enhanced using a cooling-dilution method during the PIT. A mixture of cinnamon oil, non-ionic surfactant, and water was heated above the PIT of the system, and then rapidly cooled with continuous stirring, which led to the spontaneous generation of small oil droplets. The impact of oil phase composition and surfactant concentration on the formation and stability of the nanoemulsions was determined. Cinnamon oil nanoemulsions with the smallest mean droplet diameter (101 nm) were formed using 40:60 wt% of cinnamon oil and medium chain triglyceride (MCT) in the total lipid phase. Increasing surfactant concentration significantly decreased the mean droplet diameter of the nanoemulsions but did not alter their particle morphology. In addition, using the cooling-dilution method, the nanoemulsions were stable for at least 31 days when stored at 4 °C or 25 °C.

Solid-in-Oil-in-Water Emulsions for Delivery of Lactase To Control in Vitro Hydrolysis of Lactose in Milk

There is an established need to deliver lactase in milk to retain activity during storage and hydrolyze lactose after ingestion. In this work, spray-dried lactase powder was encapsulated in solid-in-oil-in-water (S/O/W) emulsions to fabricate delivery systems. The adoption of Span 80 in milk fat and lecithin in protein solution enabled the encapsulation of ∼76% lactase and <400 nm droplets. Additional cross-linking of proteins on droplets by transglutaminase and addition of sodium caseinate effectively reduced the amount of free lactase after spray drying emulsions. Compared to the data for free lactase, encapsulation significantly improved the thermal stability of lactase, reduced the level of lactose hydrolysis during a 14 day refrigeration (from ∼70 to <20%), enabled the gradual release of lactose during the simulated gastric and intestinal digestions, and resulted in the hydrolysis of most lactose during the simulated digestions. Therefore, the studied S/O/W emulsions have the potential to deliver lactase in milk for lactose-intolerant consumers.

Freeze-dried capsules prepared from emulsions with encapsulated lactase as a potential delivery system to control lactose hydrolysis in milk

The objective of this work was to study solid/oil/water (S/O/W) emulsions as delivery systems with retained lactase in milk and controlled release during in vitro digestion. Spray-dried lactase powder was suspended in anhydrous milk fat/Span® 80 emulsified by sodium caseinate and lecithin (5:1). The S/O/W emulsion had an encapsulation efficiency of 75%, a hydrodynamic diameter of 292nm, and a zeta potential of -17.37mV. Cross-linking the dialyzed emulsion with transglutaminase eliminated the detection of free lactase after freeze-drying emulsions and the addition of sodium caseinate further preserved lactase activity. The hydrolysis of lactose in full-fat or skim milk after 3-week storage reduced from>75% for free lactase to<15% for encapsulated lactase. The encapsulated lactase was released gradually during the simulated digestions to hydrolyze lactose in milk more efficiently than free lactase. The present findings suggest S/O/W emulsions are potential delivery systems to incorporate lactase in milk products.

Recent Advances in the Utilization of Natural Emulsifiers to Form and Stabilize Emulsions

Consumer concern about human and environmental health is encouraging food manufacturers to use more natural and sustainable food ingredients. In particular, there is interest in replacing synthetic ingredients with natural ones, and in replacing animal-based ingredients with plant-based ones. This article provides a review of the various types of natural emulsifiers with potential application in the food industry, including phospholipids, biosurfactants, proteins, polysaccharides, and natural colloidal particles. Increased utilization of natural emulsifiers in food products may lead to a healthier and more sustainable food supply. However, more research is needed to identify, isolate, and characterize new sources of commercially viable natural emulsifiers suitable for food use.

Long-term stability of sodium caseinate-stabilized nanoemulsions

Oil-in-water (5 wt%) nanoemulsions were prepared with different concentration (2.5-10 wt%) of sodium caseinate as a sole emulsifier and their long-term storage stability was investigated for 6 months. Previous studies associated with sodium caseinate looked only into nanoemulsion formation; hence the challenges with long-term stability were not addressed. All nanoemulsions displayed an average droplet size <200 nm, which remained unchanged over 6 months. However, all of them displayed rapid creaming due to unabsorbed protein induced depletion flocculation, whose extent increased with protein concentration, although the cream layer formed was weak and re-dispersible upon gentle mixing. Microstructural analysis of the cream layer showed compaction of flocculated nanodroplet network with time leaving the aqueous phase out. Calculation of depletion interaction energy showed an increase in inter-droplet attraction with protein concentration and decrease with a reduction in droplet size, making the nanoemulsions more resistant to flocculation than conventional emulsions. This work aids in understanding the dependence of protein concentration on long-term stability of sodium caseinate-stabilized nanoemulsions.

Natural emulsifiers - Biosurfactants, phospholipids, biopolymers, and colloidal particles: Molecular and physicochemical basis of functional performance

There is increasing consumer pressure for commercial products that are more natural, sustainable, and environmentally friendly, including foods, cosmetics, detergents, and personal care products. Industry has responded by trying to identify natural alternatives to synthetic functional ingredients within these products. The focus of this review article is on the replacement of synthetic surfactants with natural emulsifiers, such as amphiphilic proteins, polysaccharides, biosurfactants, phospholipids, and bioparticles. In particular, the physicochemical basis of emulsion formation and stabilization by natural emulsifiers is discussed, and the benefits and limitations of different natural emulsifiers are compared. Surface-active polysaccharides typically have to be used at relatively high levels to produce small droplets, but the droplets formed are highly resistant to environmental changes. Conversely, surface-active proteins are typically utilized at low levels, but the droplets formed are highly sensitive to changes in pH, ionic strength, and temperature. Certain phospholipids are capable of producing small oil droplets during homogenization, but again the droplets formed are highly sensitive to changes in environmental conditions. Biosurfactants (saponins) can be utilized at low levels to form fine oil droplets that remain stable over a range of environmental conditions. Some nature-derived nanoparticles (e.g., cellulose, chitosan, and starch) are effective at stabilizing emulsions containing relatively large oil droplets. Future research is encouraged to identify, isolate, purify, and characterize new types of natural emulsifier, and to test their efficacy in food, cosmetic, detergent, personal care, and other products.