Monodisperse aqueous microspheres encapsulating high concentration of l-ascorbic acid: insights of preparation and stability evaluation from straight-through microchannel emulsification

Stabilization of l-ascorbic acid (⌊-AA) is a challenging task for food and pharmaceutical industries. The study was conducted to prepare monodisperse aqueous microspheres containing enhanced concentrations of ⌊-AA by using microchannel emulsification (MCE). The asymmetric straight-through microchannel (MC) array used here constitutes 11 × 104 μm microslots connected to a 10 μm circular microholes. 5-30% (w/w) ⌊-AA was added to a Milli-Q water solution containing 2% (w/w) sodium alginate and 1% (w/w) magnesium sulfate, while the continuous phase constitutes 5% (w/w) tetraglycerol condensed ricinoleate in water-saturated decane. Monodisperse aqueous microspheres with average diameters (dav) of 18.7-20.7 μm and coefficients of variation (CVs) below 6% were successfully prepared via MCE regardless of the ⌊-AA concentrations applied. The collected microspheres were physically stable in terms of their dav and CV for >10 days of storage at 40°C. The aqueous microspheres exhibited ⌊-AA encapsulation efficiency exceeding 70% during the storage.

Monodisperse W/O/W emulsions encapsulating L-ascorbic acid: Insights on their formulation using microchannel emulsification and stability studies

Stabilizing l-ascorbic acid is a challenge for food industries. The present study aimed to formulate monodisperse food-grade water-in-oil-in-water (W/O/W) emulsions containing a high concentration of l-ascorbic acid in an inner aqueous phase using homogenization and subsequent microchannel emulsification (MCE). The microchannel (MC) array plate used here was a silicon asymmetric straight-through MC array that consists of numerous 10. μm. ×. 100. μm microslots with a 30. μm depth, each connected to a 10. μm-diameter circular MC with a 70. μm depth. Water-in-oil (W/O) emulsions contained a soybean oil solution with 4-8% (w/w) tetraglycerin condensed ricinoleic acid ester as a continuous phase and an aqueous solution with 10-30% (w/v) l-ascorbic acid, 1% (w/w) magnesium sulfate, and 1% (w/v) gelatin as an inner aqueous phase. The W/O emulsion droplets formulated using a rotor-starter homogenizer had average droplet diameters of 2.6-2.9. μm and coefficients of variation (CVs) of 13-17%. MCE was performed using a dispersed W/O emulsion phase and a 5. mM phosphate buffer containing 1% (w/w) decaglycerol monolaurate and 10-30% (w/v) D(+)-glucose as an outer aqueous phase. Monodisperse W/O/W emulsions containing W/O droplets with average diameters of 26.0-31.5. μm and CVs below 10% were successfully formulated via an asymmetric straight-through MC array at a low hydrophobic emulsifier concentration, regardless of l-ascorbic acid concentration. The W/O droplets dispersed in these monodisperse W/O/W emulsions were physically stable in variation of average diameter and CV for more than 10d of storage at 4. °C. The monodisperse W/O/W emulsions also exhibited l-ascorbic acid retention exceeding 80% during storage.

A novel α-aminophosphonic acid-modified acrylamide-based hydrophobic associating copolymer with superb water solubility for enhanced oil recovery

As a non-renewable resource, the rational exploitation of oil has attracted a large amount of attention. Among many methods for enhanced oil recovery, polymer flooding is the most suitable method of chemical flooding for non-marine reservoirs and therefore various modified acrylamide-based copolymers have been studied. In this study, a novel α-aminophosphonic acid-modified hydrophobic associating copolymer was successfully synthesized by copolymerization of acrylamide, acrylic acid, N-allyldodecanamide and 1-(dimethylamino)allylphosphonic acid. The copolymer was characterized by FT-IR, 1H NMR and thermogravimetry and exhibited superior water solubility and thickening capability. Subsequently, the shear resistance, temperature resistance and salt tolerance of the copolymer solution were investigated. The value of apparent viscosity retention of a 2000 mg L-1 copolymer solution was as high as 58.55 mPa s at a shear rate of 170 s-1 and remained at 40.20 mPa s at 120 °C. The values of apparent viscosity retention of 55.41 mPa s, 59.95 mPa s and 52.97 mPa s were observed in solutions of 10000 mg L-1 NaCl, 1200 mg L-1 MgCl2, and 1200 mg L-1 CaCl2, respectively. These were better than those of partially hydrolyzed polyacrylamide under the same conditions. In addition, an increase of up to 14.52% in the oil recovery rate compared with that for water flooding could be achieved in a core flooding test using a 2000 mg L-1 copolymer solution at 65 °C.

Corrosion behaviour of direct current and active screen plasma carburised AISI 316 stainless steel in boiling sulphuric acid solutions

Active screen plasma is a recently developed plasma surface alloying technique, which has shown potential for addressing some drawbacks associated with conventional direct current plasma processes. In this study, the corrosion performance of untreated, direct current and active screen plasma carburised AISI 316 was investigated by immersion in a boiling solution of sulphuric acid. The experimental results show that the corrosion behaviour of expanded austenite produced by low temperature plasma carburising is controlled by the type and density of surface defects; the corrosion properties of the active screen plasma carburised material are superior to that produced by direct current plasma because of the significantly reduced edge effect and surface defects; and the bias level used in the active screen carburising treatment has a profound effect on the corrosion performance of the material. Based on the experimental results, the corrosion mechanisms involved are discussed.