Storage stability of food-grade bimodal oil-in-water emulsions: Effects of emulsifier type and combination

Lipids are often ingested via oil-in-water (O/W) emulsions, where interfacial properties and droplet size influence their digestibility. In this study, a bimodal O/W emulsion, termed Food Emulsion Blend (FEB), was prepared by mixing two monodisperse emulsions of different droplet sizes and compositions. The influence of droplet size and emulsifier type on in vitro digestion was evaluated. Soybean oil was used as the dispersed phase, and monodisperse emulsions were prepared via premix membrane emulsification using membranes with pore sizes of 1, 10, and 50 µm. Two selected emulsions were mixed in equal proportions to form FEB. The emulsifiers included 1.0% (w/w) Tween 20 (TW) or 0.5% (w/w) Tween 20 and 0.5% (w/w) citrus pectin (TWCP). The d4,3 values of the emulsions stabilized by TW and TWCP ranged from 1.05 to 51.99 µm and from 1.19 to 46.94 µm, respectively. In vitro digestion revealed that all FEB samples retained bimodal size distributions post-gastric digestion. Free fatty acid release correlated strongly with the initial total droplet surface area for the TW- and TWCP-stabilized FEBs (R2 > 0.8). These results suggest that FEB allows for the precise control of lipid release, offering potential applications in food formulation.

<p>Emulsions are the basis for many commercial products such as foodstuffs and paint due in part to their highly tunable flow properties. It is qualitatively understood that factors such as the dispersed phase droplet size and size distribution should affect how an emulsion flows because they influence how droplets can deform or pack. Since standard emulsification techniques such as blending and homogenization cannot produce emulsions with well-defined size distributions, little work has been done to, in particular, quantitatively determine the influence of droplet size distribution on emulsion flow properties. Consequently, in this investigation we have probed how the droplet size distribution affects emulsion flow properties by using model monodisperse emulsion systems with narrow, controllable droplet size distributions. Using a microfluidic flow focusing device, dodecane-in-water emulsions with diameters between 50 to 100 m with polydispersities less than 5% were produced, as characterized by pulsed field gradient nuclear magnetic resonance and optical microscopy. Due to the relatively large size of the droplets, it was only possible to examine the creamed phase of the emulsion. Samples of known polydispersity were made by mixing known quantities of two monodisperse emulsions. The monodisperse and bimodal emulsions were then subjected to rotational and oscillatory shear flow using a controlled stress rheometer to determine the effects of droplet size and size distribution on emulsion flow properties. Rotational and oscillatory rheological experiments showed that the monodisperse emulsions had two distinct behaviours: foam-like with appreciable thixotropy and yield stresses as well as emulsion-like with no evident thixotropy. The transition between these two behaviours appears to happen at a critical droplet radius between 33 and 37 micrometres. The rheological properties of the bimodal emulsions was split into three distinct behaviours. In samples that could be considered a matrix of large droplets perturbed by smaller droplets, the flow properties were similar to those of the constituent emulsion with the larger droplets. Increasing the number fraction of smaller droplets to a 1:1 ratio creates an entirely new phase with significantly reduced elastic properties. Surprisingly, when the emulsion primarily consists of small droplets, the flow properties are most similar to that of the large droplets. Additionally, despite the microstructural differences, all emulsions showed flow characteristics typical of soft glassy materials above the glass transition temperature. These results demonstrate the significant influence of microstructure on emulsion rheology, where altering the droplet size or polydispersity essentially creates a new phase with its own unique flow properties that is not simply a combination of the properties of the individual monodisperse components that make up the sample</p>

<p>Emulsions are the basis for many commercial products such as foodstuffs and paint due in part to their highly tunable flow properties. It is qualitatively understood that factors such as the dispersed phase droplet size and size distribution should affect how an emulsion flows because they influence how droplets can deform or pack. Since standard emulsification techniques such as blending and homogenization cannot produce emulsions with well-defined size distributions, little work has been done to, in particular, quantitatively determine the influence of droplet size distribution on emulsion flow properties. Consequently, in this investigation we have probed how the droplet size distribution affects emulsion flow properties by using model monodisperse emulsion systems with narrow, controllable droplet size distributions. Using a microfluidic flow focusing device, dodecane-in-water emulsions with diameters between 50 to 100 m with polydispersities less than 5% were produced, as characterized by pulsed field gradient nuclear magnetic resonance and optical microscopy. Due to the relatively large size of the droplets, it was only possible to examine the creamed phase of the emulsion. Samples of known polydispersity were made by mixing known quantities of two monodisperse emulsions. The monodisperse and bimodal emulsions were then subjected to rotational and oscillatory shear flow using a controlled stress rheometer to determine the effects of droplet size and size distribution on emulsion flow properties. Rotational and oscillatory rheological experiments showed that the monodisperse emulsions had two distinct behaviours: foam-like with appreciable thixotropy and yield stresses as well as emulsion-like with no evident thixotropy. The transition between these two behaviours appears to happen at a critical droplet radius between 33 and 37 micrometres. The rheological properties of the bimodal emulsions was split into three distinct behaviours. In samples that could be considered a matrix of large droplets perturbed by smaller droplets, the flow properties were similar to those of the constituent emulsion with the larger droplets. Increasing the number fraction of smaller droplets to a 1:1 ratio creates an entirely new phase with significantly reduced elastic properties. Surprisingly, when the emulsion primarily consists of small droplets, the flow properties are most similar to that of the large droplets. Additionally, despite the microstructural differences, all emulsions showed flow characteristics typical of soft glassy materials above the glass transition temperature. These results demonstrate the significant influence of microstructure on emulsion rheology, where altering the droplet size or polydispersity essentially creates a new phase with its own unique flow properties that is not simply a combination of the properties of the individual monodisperse components that make up the sample</p>

Generation of highly uniform droplets using asymmetric microchannels fabricated on a single crystal silicon plate: Effect of emulsifier and oil types

This paper investigated the generation characteristics of nonspherical oil-in-water (O/W) droplets consisting of food-grade components using microchannel (MC) array devices that have many rectangular MCs with shallow wells. The well height was designed to be twice the MC height. Two hydrophilic MC array devices made of surface-oxidized single-crystal silicon with equivalent MC diameters of 3.2 and 8.4 μm were used. Refined soybean oil was used as the to-be-dispersed phase, and a Milli-Q water solution of 1.0 wt% polyoxyethylene (20) sorbitan monolaurate (Tween20) was used as the continuous phase. Highly uniform discoid droplets with diameters of 9.0 and 21.5 μm, heights of 4.6 and 9.8 μm, and coefficients of variation of less than 4% were generated by simply forcing a to-be-dispersed phase via rectangular MCs into a well filled with a continuous phase. The to-be-dispersed phase pressures necessary for droplet generation were less than 8 kPa. The detailed generation process of the discoid droplets was analyzed using movie clips taken by a high-speed camera. Key phenomena during the detachment process were considered to be rapid flow of the to-be-dispersed phase into the well and instantaneous pinch-off of the neck. The effect of the to-be-dispersed phase velocity inside a rectangular MC (Ud,MC) on the resultant droplet diameter and the droplet-generation rate was also analyzed. Size-controlled discoid droplets were stably generated via the rectangular MC below the critical Ud,MC, and the droplet-generation rate became maximum at the critical Ud,MC.

Preparation of monodispersed emulsions by premix membrane emulsification without repetitive permeation: Influence of membrane permeation rate (flux) and emulsion viscosity

Tomatoes are a major crop for global exports and have significant nutritional benefits. However, their lifespan is limited due to various biotic and abiotic factors. This study aimed to formulate an edible coating using crude alfalfa saponins coupled with decaglycerol monolaurate (ML-750) and polyoxyethylene (20) sorbitan monolaurate (Tween 20), to enhance the postharvest quality and shelf life of tomatoes by preventing spoilage. The effectiveness of alfalfa saponins coatings, both alone, and with ML-750 and Tween 20, was evaluated by comparing their impact on color, texture, overall acceptability, and % weight loss at 4°C and 25°C for 7 days. Significant improvements were observed in the quality attributes of tomatoes, including firmness, aroma, color, texture, and overall acceptability. Crude alfalfa saponins in emulsified form with Tween 20 increased the shelf stability of tomatoes more effectively than uncoated and ML-750 combined coatings. The total soluble solids (TSS) and pH also play a crucial role in determining the quality of the fruits. The results indicated no significant changes in the TSS of tomatoes coated with encapsulated saponins. Subsequently, a gradual increase in the pH of the coated tomatoes was observed on days 5 and 7, respectively. The findings of this study revealed that alfalfa saponins coupled with synthetic emulsifiers may be a beneficial strategy for prolonging the shelf life and improving the postharvest quality of tomatoes.

Spray dried double emulsions containing procyanidin-rich extracts produced by premix membrane emulsification: Effect of interfacial composition

Production of quality greenhouse and nursery crops is dependent on high quality and quantities of water. At present, in some regions, insufficient water supply is a growing concern. This study was conducted to evaluate growth of New Guinea impatiens (Impatiens hawkerii 'Celebrate Salmon'), when watered with a polyoxyethylenesorbitan monolaurate (C58H114O26) solution commercially known as Tween 20, at differing irrigation levels compared with a conventional water regimen without the surfactant, and also to determine how Tween 20 would affect photosynthesis and transpiration. The treatment design was a 3 by 6 complete factorial design plus a control. The two factors were irrigation and Tween 20. Irrigation levels of 20%, 40%, or 60% of the full crop evapotranspiration (ET) requirements were used in combination with Tween 20 concentrations of either 0, 25, 50, 75, 100, or 125 mg·L−1 (0, 0.003338, 0.00668, 0.0100145, 0.01335, or 0.01669 oz per gallon). The control group was watered with tap water to container capacity with about 30% leachate. Evapotranspiration was determined as the difference of the applied water amount minus the leachate of the control. Plants irrigated with Tween 20 from 25 to 125 mg·L−1 (0.003338 to 0.01669 oz per gallon) at the 40% or 60% irrigation level had the same height and growth index as plants in the control after three months of growth. Plant fresh and dry weights were not different between the control and the treatments of Tween 20 from 50 to 125 mg·L−1 (0.00668 to 0.01669 oz per gallon) at the 60% irrigation level or the treatment of Tween 20 at 100 mg·L−1 (0.01335 oz per gallon) at the 40% irrigation level. Tween 20 had no effect on net photosynthetic rate. Tween 20 decreased the amount of transpired water of New Guinea impatiens 'Celebrate Salmon'. When the Tween 20 concentration increased from 0 to 100 mg·L−1 (0 to 0.01335 oz per gallon) at the 60% irrigation level, the transpiration rate and stomatal conductance decreased markedly by 43% and 47%, respectively, and water use efficiency was increased by 47%. Results from this study suggest that Tween 20 is able to increase plant water use efficiency through regulation of stomatal conductance or transpiration under deficit irrigation.Index words: irrigation management, chemigation, source-sink physiology, deficit irrigation, wetting agent, Tween 20, adjuvant.Species used in this study: New Guinea Impatiens (Impatiens hawkerii W. Bull. 'Celebrate Salmon').Chemicals used in this study: Tween 20 (polyoxyethylenesorbitan monolaurate). (aka: polysorbate 20, polyoxyethylene (20) sorbitan monolaurate)

Microfluidic techniques for producing emulsions have been proposed over the last decade. Major advantages of microfluidic techniques include the production of monodisperse emulsions with a coefficient of variation (CV) of typically <5%, superior controllability of droplet size and monodispersity, and in situ microscopic monitoring. Microchannel (MC) emulsification, proposed by our research group, is a unique and robust technique to produce monodisperse emulsions with controlled droplet sizes of >1 μm. In MC emulsification, droplet generation via MC arrays does not require any external shear/elongational stress; i.e., the dispersed phase that passed through MCs is transformed spontaneously into uniform droplets due to hydrodynamic instability of the oil-water interface. Here we present some of the recent findings obtained from MC emulsification studies and the controlled production of monodisperse submicron emulsions by novel nanochannel (NC) emulsification. The first topic on MC emulsification is the influence of operating temperature (10 to 70 °C) on production of oil-in-water (O/W) emulsions using a surface-oxidized silicon MC array plate with an MC depth of 8 μm. The droplet generation results were correlated well with the contact angle of the dispersed phase to the MC walls that was measured using a novel method using parallel long MCs. Another topic on MC emulsification is the development of stainless-steel MC emulsification devices. Stainless-steel MC array plates with an MC depth of 100 or 150 μm were mechanically fabricated using an end mill. The use of the stainless-steel MC array plates enabled stably producing monodisperse O/W emulsions with an average droplet diameter of up to 550 μm. We also recently developed silicon NC array plates with the smallest NC depth of 50 nm. NC emulsification experiments demonstrated successful production of monodisperse submicron O/W emulsions with the smallest average droplet diameter of 480 nm. The diameter of the droplets generated by NC emulsification was measured by a novel technique that exploits nanospace.

Monodisperse emulsions can be obtained by applying a shear step to a crude polydisperse one [1]. In this paper, we first describe the mechanisms and conditions for the occurrence of this transformation. The fragmentation process involves two distinct regimes. At short time (shorter than one second), the droplet diameter decreases abruptly. The droplets deform into long threads that undergo a Rayleigh instability. The obtained diameter is mainly determined by the applied stress and weakly depends on the viscosity ratio between the dispersed and continuous phases. However, this last parameter is determining for monodispersity. After this first step, the resulting droplets can, once again, break up into daughter droplets. This second mechanism is much slower, with a characteristic time of several hundred seconds, and much less efficient for fragmentation. A large variety of calibrated materials (direct, inverted, multiple emulsions and suspensions) can be obtained following this monodisperse fragmentation process. PACS numbers: 82.70.Kj, 82.70.-y, 77.84.Nh

Nutritional and pathological effects of sorbitan monolaurate, polyoxyethylene sorbitan monolaurate and polyoxyethylene monolaurate when fed to hamsters

The droplet size and uniformity of water-in-oil (W/O) emulsions are important properties governing their stability in diverse applications. Monodisperse emulsions are preferred over polydisperse emulsions because their droplet size and distribution are easier to control. Here, we prepared (relatively) monodisperse W/O emulsions using microchannel homogenization (MCH) with an asymmetric straight-through microchannel (MC) array chip. Numerous asymmetric straight-through MCs, each comprising a microslot and circular microhole (diameter: 10 µm), were microfabricated on a silicon-on-insulator chip. We investigated the effects of emulsifier concentration, continuous-phase viscosity, dispersed-phase volume fraction, and the operating pressure of coarse W/O emulsions on the preparation of W/O emulsions, droplet size, and size distribution. The continuous phase was composed of soybean or medium-chain triglyceride oil solutions with tetraglycerin monolaurate condensed ricinoleic acid ester as the emulsifier. The dispersed phase was a Milli-Q water solution containing NaCl and/or polyethylene glycol (m.w. 20,000). The results demonstrate the suitability of MCH for the preparation of monodisperse W/O emulsions with an average droplet diameter of 12–15 µm and 8% lowest coefficient of variation using hydrophobically surface-treated asymmetric straight-through MCs with appropriately selected emulsion compositions and operating conditions.

Phase transitions in emulsified even‐numbered n‐alkanes (C16, C18, and C20) are studied as a function of droplet size (0.15–3.45 μm) and surfactant type (polyoxyethylene sorbitan monolaurate or caseinate) using microcalorimetry (DSC) and ultrasonic attenuation measurements (2.25 MHz). Two DSC exothermic peaks were observed during the heating of C18 and C20 emulsions stabilized by Tween 20: a minor peak around 15 and 25 °C, respectively, and a major double peak about 10 °C higher. We tentatively attribute the minor peak to crystal‐rotator phase transition, and the split major peak to melting of the surface and core of the droplets. The C16 emulsions showed similar behavior for the major melting peak (15 °C), but the minor peak was absent‐possibly as the sample was not cooled enough to cause the rotator phase to enter the low temperature crystalline state. For similar sodium caseinate stabilized emulsions of C18 and C20, the minor peak was much less pronounced (~25%), which we attribute to the lack of compatibility between the alkane and protein molecules. There were two ultrasonic attenuation peaks for the melting of C18 and C20 and one for C16 corresponding to the DSC peaks. In all cases, the magnitude of the attenuation decreased with increasing particle size. Using an extended scattering theory approach we were able to relate the changes in ultrasonic attenuation to the changes in the effective physical properties of the alkane molecules during melting.

Effect of membrane parameters on the size and uniformity in preparing agarose beads by premix membrane emulsification