Yinghe He

Encapsulation Efficiency of Food Flavours and Oils during Spray Drying

Microencapsulation is a rapidly expanding technology which is a unique way to package materials in the form of micro- and nano-particles, and has been well developed and accepted within the pharmaceutical, chemical, food and many other industries. Spray drying is the most commonly used encapsulation technique for food products. A successful spray drying encapsulation relies on achieving high retention of the core materials especially volatiles and minimum amounts of the surface oil on the powder particles for both volatiles and non-volatiles during the process and storage. The properties of wall and core materials and the prepared emulsion along with the drying process conditions will influence the efficiency and retention of core compounds. This review highlights the new developments in spray drying microencapsulation of food oils and flavours with an emphasis on the encapsulation efficiency during the process and different factors which can affect the efficiency of spray drying encapsulation.

Nano-Emulsion Production by Sonication and Microfluidization—A Comparison

The efficiency of sonication and microfluidization to produce nano-emulsions were evaluated in this study. The purpose was to produce an oil-in-water nano-emulsion of d-limonene to apply it in the next step for nano-particle encapsulation. In the entrapment and retention of volatiles or for the microencapsulation efficiency, emulsion size is one of the critical factors. In this study, a bench-top sonicator and an air-driven microfluidizer were used to prepare the emulsions. Results show that, while both methods were capable of producing nano-emulsions of the size range of 150–700 nm, the microfluidizer produced emulsions with narrower size distributions and sonication was more convenient in terms of operation and cleaning. In general, the size of the emulsions decreased with increasing sonication time, or the microfluidization pressure and duration. However, for both sonication and microfluidization, optimal conditions were necessary for emulsification beyond which the emulsion sizes would either increase or have little change with further processing.

Encapsulation of Nanoparticles of d-Limonene by Spray Drying: Role of Emulsifiers and Emulsifying Techniques

Submicron emulsion particles of d-limonene prepared by a microfluidizer and ultrasound were spray dried to produce nanoparticle encapsulated powders. Maltodextrin combined with a surface-active biopolymer (modified starch or whey protein concentrate) or a small molecule surfactant (Tween 20) was used as the wall material. Results showed that microfluidization was an efficient emulsification technique resulting in a powder with the highest retention (86.2%) of d-limonene, mainly due to its capability to produce emulsions with fairly small droplets (d 43 of 700–800 nm) and narrow distributions, which had a good stability during the process. Among different emulsifiers used, although Tween 20 significantly reduced the emulsion size (d 43 < 200 nm), the resulted powder had the poorest encapsulation efficiency.

Role of Powder Particle Size on the Encapsulation Efficiency of Oils during Spray Drying

In this study, emulsions prepared by microfluidizer and ultrasound were spray-dried to produce encapsulated powders containing d-limonene or fish oil (20% w/w). Maltodextrin combined with a surface-active biopolymer (modified starch or whey protein concentrate) was used as the wall material (40% solids w/w). It was shown that volatility of the core material significantly affects the surface oil content of the encapsulated powder. Also, by the classification of encapsulated powders into various sizes, our results revealed that larger particles (>63 µm) retain more volatiles than smaller ones (<38 µm), but at the same time there is more unencapsulated oil at the surface of big particles. In the case of fish oil, although surface oil content obtained by solvent extraction was high in larger particles, X-ray photoelectron spectroscopy analysis showed that different particles had similar surface oil coverage.

Formation of surface nanodroplets under controlled flow conditions.

Significance Solvent exchange is a generally used approach for producing many nanoscale droplets on an immersed substrate. In this process, a good solvent is displaced by a poor solvent of oil, leading to oil nanodroplet nucleation and subsequent growth on the substrate. This work is, to our knowledge, the first attempt to quantitatively understand the relationship between the droplet size and the flow conditions during the solvent exchange, and to pave the way for the droplet size control. The experimental results show that the droplet volume increases with increasing Peclet number of the flow as ∝Pe3/4, in good agreement with our theoretical analysis. We also reveal that the buoyancy effects contribute to the formation of bigger and less homogeneously distributed droplets in less-narrow channels. Nanodroplets on a solid surface (i.e., surface nanodroplets) have practical implications for high-throughput chemical and biological analysis, lubrications, laboratory-on-chip devices, and near-field imaging techniques. Oil nanodroplets can be produced on a solid–liquid interface in a simple step of solvent exchange in which a good solvent of oil is displaced by a poor solvent. In this work, we experimentally and theoretically investigate the formation of nanodroplets by the solvent exchange process under well-controlled flow conditions. We find significant effects from the flow rate and the flow geometry on the droplet size. We develop a theoretical framework to account for these effects. The main idea is that the droplet nuclei are exposed to an oil oversaturation pulse during the exchange process. The analysis shows that the volume of the nanodroplets increases with the Peclet number Pe of the flow as ∝Pe3/4, which is in good agreement with our experimental results. In addition, at fixed flow rate and thus fixed Peclet number, larger and less homogeneously distributed droplets formed at less-narrow channels, due to convection effects originating from the density difference between the two solutions of the solvent exchange. The understanding from this work provides valuable guidelines for producing surface nanodroplets with desired sizes by controlling the flow conditions.

A simple method for the preparation of monodisperse protein-loaded microspheres with high encapsulation efficiencies

A simple method for the preparation of monodisperse protein-loaded polymer microspheres is presented in this paper. The method is based on the co-extrusion of an internal phase of an aqueous protein solution and an external phase of an organic polymer solution through a 200-micron-sized hole. Controlled in the correct flow region, this process produces a core-shell-structured laminar liquid jet, which breaks to form monodisperse compound liquid droplets. Stabilized in a dilute aqueous polyvinyl alcohol (PVA) solution, the droplets are converted into solid protein-loaded polymer microspheres through evaporation of the organic solvent. Results show that preparation parameters such as polymer concentration, total flow rate, flow rate ratio of the aqueous to organic phase have significant effects on the mean particle size, particle morphology and protein encapsulation efficiency (EE). The results of biodegradation and the protein release characteristics of the polymer microspheres are also presented.

Lithium recycling and cathode material regeneration from acid leach liquor of spent lithium-ion battery via facile co-extraction and co-precipitation processes

A novel process for extracting transition metals, recovering lithium and regenerating cathode materials based on facile co-extraction and co-precipitation processes has been developed. 100% manganese, 99% cobalt and 85% nickel are co-extracted and separated from lithium by D2EHPA in kerosene. Then, Li is recovered from the raffinate as Li2CO3 with the purity of 99.2% by precipitation method. Finally, organic load phase is stripped with 0.5M H2SO4, and the cathode material LiNi1/3Co1/3Mn1/3O2 is directly regenerated from stripping liquor without separating metal individually by co-precipitation method. The regenerative cathode material LiNi1/3Co1/3Mn1/3O2 is miro spherical morphology without any impurities, which can meet with LiNi1/3Co1/3Mn1/3O2 production standard of China and exhibits good electrochemical performance. Moreover, a waste battery management model is introduced to guarantee the material supply for spent battery recycling.

Controlled evolution from multilamellar vesicles to hexagonal mesostructures through the addition of 1,3,5-trimethylbenzene

Self-assembled porous silica materials with adjustable structures and tunable pore sizes have important applications in catalysis, separation, and nanoscience. Organic cosolvents such as 1,3,5-trimethylbenzene (TMB) can be used to synthesize large pore mesoporous materials. In this study, we systematically studied the influence of the time of TMB addition on the self-assembled organic/inorganic composite structures in a nonionic block copolymer templating system. By controlling the time at which TMB is added to the system, an evolution from multilamellar vesicle to ordered hexagonal mesostructure has been observed. TMB is a swell agent in our synthesis, an increase in the delay of TMB addition can kinetically reduce the amount of TMB penetrating into the hydrophobic core of embryonic mesostructure, leading to cooperatively self-assembled vesicular and mesostructured materials with decreased packing parameters. Our results have shown that, in the simple synthesis system of traditional SBA-15 material, siliceous materials with a range of structures can be rationally designed and synthesized through the addition of TMB at different times. Such materials with tunable pore structures have potential applications as microcapsules and controlled release/delivery carriers.

Experimental study of drop-interface coalescence in the presence of polymer stabilisers

Abstract An experimental study has been carried out to characterise the performance of polymer stabilisers, partially hydrolysed polyvinyl acetate (PVAc), used in suspension polymerisation processes. The stabilisers are ranked by their ability to stabilise the dispersion characterised by the median coalescence time of a single drop with its homophase at a planar liquid/liquid interface. Results show that the stability of the dispersion relates closely to the molecular properties of the PVAcs. Other conditions being equal, PVAcs with higher molecular weights or lower degrees of hydrolysis can better stabilise a liquid–liquid dispersion. The stability of the dispersion also depends strongly on where the PVAc resides. The presence of a PVAc in the dispersed phase significantly reduces stability. Consistent with results reported in the literature, considerable scatter has been observed on the coalescence times of identical drops under the same conditions. An explanation for the scatter is also proposed in the paper, based on the classical Reynolds model for film thinning.

Morphology and Preferred Orientation of Pulse Electrodeposited Magnesium

A nanocrystalline magnesium material with a high specific surface area is expected to react rapidly and reversibly with hydrogen gas to yield magnesium hydride, a hydrogen storage medium. In this paper, the feasibility of the synthesis of magnesium materials for hydrogen storage applications by pulse electrodeposition of magnesium from ethereal electrolytes containing Grignard reagents was investigated. Deposition onto flat stainless steel electrodes established that, as in dc deposition, the morphology of the deposits varied widely with electrolyte composition and charge density. Irregular, nanocrystalline magnesium films were formed at low current density (0.4 mA cm^−2) and low charge density (1 C cm^−2) using butylmagnesium chloride electrolytes in dibutyl diglyme, while at a higher current density (15 mA cm^−2) in tetrahydrofuran, dense films were favored.