Factors Affecting Initial Retention of a Microencapsulated Sunflower Seed Oil/Milk Fat Fraction Blend

To study the effect of emulsion stability, particle size, emulsifier, and crystalline fat in the oil phase on initial retention of a low-trans fat encapsulated in a trehalose matrix, six emulsions were prepared. The six emulsions were formulated with 20 wt% trehalose solution as the aqueous phase, a lipid phase either with no crystalline fat, sunflower seed oil (SFO), or with a crystalline phase, a 40% SFO in high-melting fraction of milk fat (HMF) blend, and sodium caseinate (NaCas), a 50 wt% blend of the palmitic sucrose esters (SE) P-170 and P-1670, or a 50 wt% blend of NaCas/SE as stabilizers. Particle size did not change or it changed only slightly during the freeze thaw or freeze drying process when the fat phase was SFO. However, when a crystalline phase was present, the volume-weighted mean diameter (D _4,3) increased dramatically for SE and NaCas/SE stabilizers. Encapsulation properties were determined by the counteracting effects of particle size and distribution, the presence of crystalline material in the droplets and interactions between interface components, fat phase and trehalose. In addition, retention was less related to emulsion stability. The emulsions selected for this study were stable for at least 30 h which was enough for obtaining a high degree of encapsulation.     

Water Sorption,Glass Transition,and Microstructures of Refractance Window– and Freeze-Dried Mango (Philippine “Carabao” Var.) Powder

Water sorption isotherms, glass transition, and microstructures of Refractance Window (RW)– and freeze-dried Philippine “Carabao” mango powders were investigated. Water sorption isotherms were developed by the isopiestic method, while thermal transition of the powders, at various water activities (a _w  = 0.11–0.86), was determined using differential scanning calorimetry (DSC). The sorption isotherms of RW- and freeze-dried (FD) mango powders exhibited a type III sigmoidal curve, showing higher and lower adsorption capacities above and below 0.5 a _w , respectively. A significant difference (p < 0.05) in water content of RW- and freeze-dried mango powders for equivalent water activities was obtained above 0.5 a _w . The onset glass transition temperature (T _gi ) of RW- and freeze-dried mango powder solids decreased as the water content increased. There were no significant differences (p ≥ 0.05) in T _gi of RW- and freeze-dried mango powder solids at constant water activities, except for a _w  = 0.86. Microscopic examination of mango powders indicated that freeze-dried mango powders exhibited greater surface area and porosity in comparison to RW-dried mango powders.     

Polymorphism and growth behavior of low-trans fat blends formulated with and without emulsifiers

Polymorphism and growth behavior of blends of a high-melting fraction of milk fat (HMF) and sunflower oil (SFO) formulated with and without the addition of sucrose esters (SE) P-170, P-1670, and S-170 were studied by pulsed ¹H NMR spectroscopy, X-ray diffraction, and polarized light microscopy. The effect of SE on the solid content maximum (S _max) or crystallization rate was observed only at low supercooling (values of ΔT below 15°C). The Avrami k _n decreased as n values increased, indicating that SE inhibited growth and impeded nucleation. Addition of SFO modified the polymorphic behavior of milk fat, most likely owing to the increase in the C₅₄ fraction (mostly 18∶1 cis) in crystals composition. P-170 and S-170 modified the polymorphic behavior of HMF when it crystallized in the α-form or in blends with up to 40% SFO at all crystallization temperatures (T _c ) selected. Addition of P-170 and S-170 favored crystallization in the β′-form, and the appearance of the β-form was delayed. P-1670 had no effect on polymorphism. When HMF and the blends were crystallized under dynamic conditions, addition of P-170 and S-170 markedly decreased crystal sizes. P-1670, however, showed no effect on microstructure.     

Enzymatic Synthesis of Feruloylated Lipids: Comparison of the Efficiency of Vinyl Ferulate and Ethyl Ferulate as Substrates

A facile and efficient enzymatic synthesis approach to synthesize feruloylated lipids, which are composed of 1(3)-feruloyl-monooleyl-glycerol and 1(3)-feruloyl-dioleyl-glycerol, through lipase-catalyzed transesterification using vinyl ferulate (VF) and ethyl ferulate (EF) as substrate, respectively, with triolein was developed. When VF was used as substrate, a maximum of conversion yield of 91.1% was obtained at 55 °C, 20 mg/mL enzyme content, water activity (a _w) = 0.07, 62 h. This was greater than that when EF was used as substrate (69.6%, 50 °C, 33.3 mg/mL enzyme content, a _w = 0.07, 96 h). Candida antarctica lipase (Novozym 435) can be reused for 13 runs without evident loss in activity and stability when VF was used as substrate. The results demonstrate that VF has greater synthetic efficiency and it provides another effective approach to prepare feruloylated lipids under normal pressure, making industry application feasible.     

The Chlorophyll Catabolite,Pheophorbide <Emphasis Type="Italic">a</Emphasis>, Confers Predation Resistance in a Larval Tortoise Beetle Shield Defense

Larval insect herbivores feeding externally on leaves are vulnerable to numerous and varied enemies. Larvae of the Neotropical herbivore, Chelymorpha alternans (Chrysomelidae:Cassidinae), possess shields made of cast skins and feces, which can be aimed and waved at attacking enemies. Prior work with C. alternans feeding on Merremia umbellata (Convolvulaceae) showed that shields offered protection from generalist predators, and polar compounds were implicated. This study used a ubiquitous ant predator, Azteca lacrymosa, in field bioassays to determine the chemical constitution of the defense. We confirmed that intact shields do protect larvae and that methanol-water leaching significantly reduced shield effectiveness. Liquid chromatography-mass spectrometry (LC-MS) of the methanolic shield extract revealed two peaks at 20.18 min and 21.97 min, both with a molecular ion at m/z 593.4, and a strong UV absorption around 409 nm, suggesting a porphyrin-type compound. LC-MS analysis of a commercial standard confirmed pheophorbide a (Pha) identity. C. alternans shields contained more than 100 μg Pha per shield. Shields leached with methanol-water did not deter ants. Methanol-water-leached shields enhanced with 3 μg of Pha were more deterrent than larvae with solvent-leached shields, while those with 5 μg additional Pha provided slightly less deterrence than larvae with intact shields. Solvent-leached shields with 10 μg added Pha were comparable to intact shields, even though the Pha concentration was less than 10% of its natural concentration. Our findings are the first to assign an ecological role for a chlorophyll catabolite as a deterrent in an insect defense.     

Synthesis and regular reflection property of cocoon-like poly(methyl methacrylate) particles by seeded suspension polymerization

Synthesis and optical properties of cocoon-like poly(methyl methacrylate) (CPM) particles in the size range of D _n  = 3.0–6.5 μm were studied. The synthesis of these anisotropic particles consists of two steps. The spherical poly(methyl methacrylate) (PMA) particles (D _n  = 2.2–5.5 μm) cross-linked by 0.2–0.8 wt% ethylene glycol dimethacrylate (EGDMA) were prepared by dispersion polymerization, using a combination of poly(vinyl pyrrolidone) (PVP) and sodium di-(2-ethylhexyl) sulfosuccinate (NaEHS) as a stabilizer in 94:840 water–methanol. Then, a suspension polymerization of 9:1 methyl methacrylate (MMA)/EGDMA in the presence of the PMA particles as seed at 85 °C in water gave non-spherical, cocoon-like CPM particles, depending on the cross-linking densities of PMA particles. The cocoon-like CPM particles (D _n,c  = 4.0 μm) showed the characteristic features of regular reflection, which can not be attained for conventional poly(methyl methacrylate) particles with a spherical shape. The effects of seed PMA particles with different properties on the formation of cocoon-like CPM particles and their regular reflection properties are described.     

Effects of ionic strength and pH on the diffusion coefficients and conformation of chitosans molecule in solution

The effects of ionic strength and pH on the diffusion coefficients and gross conformation of chitosan molecules in solution were studied. Chitosan with 83% degree of deacetylation (DD) was prepared from red shrimp (Solemocera prominenitis) processing waste. Ten different molecular weight chitosans were prepared by ultrasonic degradation, and their molecular weights were determined by static light scattering. The weight-average molecular weight (M_w) were between 78 to 914 kilo dalton (KDa). Solution of different ionic strengths (I = 0.01, 0.10, and 0.20) but the same pH (2.18) and different pHs (2.37, 3.10, and 4.14) but the same ionic strength (I = 0.05) were prepared to measure their mutual diffusion coefficient (D_m). The diffusion coefficients for standard condition (D_20,w) were derived from D_m. Intrinsic viscosities ([η]) were determined by a capillary viscometer in different pH solutions. The Mark–Houwink exponents a and ε were obtained from plots of Log [η] and Log D_20,w versus Log M_w, respectively. The results show that diffusion coefficients increased with increasing ionic strength or with increasing pH or with decreasing M_w. Value of ε and a were between 0.503 to 0.571 and ranged from 0.543 to 0.632, respectively. The results indicates that chitosans conformation were in random coil in solutions in the ranges of ionic strength and pH studied. The values of a*, ε* and a**, ε**, Mark–Houwink exponents of smaller and higher than 223 KDa chitosans, respectively, were between 0.752 to 0.988 and 0.585 to 0.777 for smaller M_w chitosans and 0.406 to 0.428 and 0.430 to 0.518 for larger M_w chitosans, respectively. Molecular-weight-induced conformational transition occurred because smaller M_w chitosans was more extended than higher M_w chitosans. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2041–2050, 1999     

Spray Drying of Skim Milk Mixed with Milk Permeate: Effect on Drying Behavior,Physicochemical Properties,and Storage Stability of Powder

The possibility of using milk permeate (MP) to lower the protein level of skim milk powder (SMP) in producing powders of 34% and lower protein is explored. Skim milk suspensions with various levels of MP were prepared by mixing SMP and MP powder (MPP) at the ratios of 1:0, 7:3, 3:7, and 0:1: from 34 to 5.3% protein. The suspensions were dried in a spray dryer with inlet and outlet temperatures of 180 and 80°C, respectively. Increasing permeate concentration in the mixture showed a greater tendency to stickiness manifested by lowered the cyclone recovery of the powder as more powder stuck on the wall of the dryer. Increasing permeate concentration in the resultant powder did not significantly affect the bulk density but led to a reduction in the particle size and also made the powder slight green and yellowish in color. It also found to lower the glass transition temperature (T_g ) of the skim milk powder (SMP) and induce crystallization of lactose at lower water activity (a_w  ≥ 0.328 for SMP:MPP of 3:7 and 0:1 compared to a_w  ≥ 0.0.432 for SMP:MPP of 1:0 and 3:7). Addition of MP in SMP lowered the T_g values of the resulting powders. The permeate fraction in spray-dried SMP/MPP mixtures found to lower the critical a_w and moisture content, suggesting the SMP mixed with MPP is more likely to become sticky than SMP alone (at 34% protein) when stored at a similar water activity and moisture content.     

Synthesis of novel biodegradable material poly(lactic acid-trimesic acid) via direct melt copolycondensation and its characterization

Directly starting from lactic acid (LA) and trimesic acid (TMA), novel biodegradable material poly(lactic acid-trimesic acid) (PLT), a modified polylactic acid (PLA) with terminal carboxyl, was synthesized via melt copolycondensation. The optimal synthetic conditions, including catalyst kinds and dosage, prepolymerization time, copolymerization temperature and time, were discussed. When L-lactic acid (L-LA) and TMA as molar feed ratio n(L-LA)/n(TMA) 120/1 was prepolymerized for 8 h at 140 °C, the copolycondensation catalyzed by 0.9 wt % SnCl₂ at 190 °C for 8 h gave PLT with the biggest intrinsic viscosity ([η]) 1.91 dL∙g⁻¹, and the corresponding weight-average molecular weight (M_w) was 14,100 Da. Serial L-PLTs at different molar feed ratios were synthesized and characterized with FTIR, ¹H NMR, GPC, DSC, and XRD. Increasing n(L-LA), M_w increased first, and the biggest M_w was 17500 Da at n(L-LA)/ n(TMA) 240/1, then decreased. Using D,L-lactic acid (D,L-LA) instead of L-LA, the influences of LA stereochemical configuration were investigated. The peak phenomenon of M_w was similar, but the biggest M_w was 23,100 Da at n(D,L-LA)/n(TMA) 320/1. The serial L-PLTs had a certain crystallinity (10.2%∼23.0%), while all D,L-PLTs were amorphous. These differences may be in touch with the reaction mechanism of direct melt copolycondensation. The method was simple and practical for the synthesis of PLA biomedical materials applied in drug delivery carrier, and vessel substitution material.     

Synthesis and characterization of PES/PSF/PEG by immersion precipitation for Mediterranean seawater desalination by FO membrane

In the present study, a simple, inexpensive, nontoxic, and environmentally friendly polyethylene glycol (PEG) polymer was used to enhance the hydrophilicity of the forward osmosis (FO) membrane using various PEG concentrations as a pore forming agent in the casting solution of polyethersulfone/polysulfone (PES/PSF) blend membranes. A nonwoven PES/PSF FO blend membrane was fabricated via the immersion precipitation phase inversion technique. The membrane dope solution was cast on polyethylene terephthalate (PET) nonwoven fabric. The results revealed that PEG is a pore forming agent and that adding PEG promotes membrane hydrophilicity. The membrane with 1 wt% PEG (PEG1) had about 27% lower contact angle than the pristine blend membrane. The PEG1 membrane has less tortuosity (which reduces from 3.4–2.73), resulting in a smaller structure parameter (S value) of 277 μm, due to the presence of open pores on the bottom surface structure, which results in diminished ICP. Using 1 M NaCl as the draw solution and distilled water as the feed solution, the PEG1 membrane exhibited higher water flux (136 L m⁻² h⁻¹) and lower reverse salt flux (1.94 g m⁻² h⁻¹). Also, the selectivity of the membrane, specific reverse salt flux, (J_s/J_w) showed lower values (0.014 g/L). Actually, the PEG1 membrane has a 34.6% higher water flux than the commercial nonwoven-cellulose triacetate (NW-CTA) membrane. By means of varied concentrations of NaCl salt solution (0.6, 1, 1.5, and 2 M), the membrane with 1 wt% PEG showed improved FO separation performance with permeate water fluxes of 108, 136, 142, and 163 L m⁻² h⁻¹. In this work, we extend a promising gate for designing fast water flux PES/PSF/PEG FO blend membranes for water desalination.     

The effect of solids on the dense phase gas fraction and gas–liquid mass transfer at conditions close to the heterogeneous regime in a mechanically agitated vessel

In the heterogeneous regime, there is a strong literature evidence (discussed herein) that solids can supplant small bubbles in the dense phase and reduce the gas hold-up. This work examines the effects of the addition of 205 μm glass ballotini on the gas hold-up and k_La in a 0.286 m diameter stirred tank operated under intense conditions (P/V ≥ 5 kW m⁻³) close to the heterogeneous regime and above the agitator speed corresponding to the just suspended point, N_JS. The tests were carried out on two systems: air–water (coalescing) and air–0.2 M sodium sulphate (salt) solution (which resists coalescence in the bubble regime). For the air–water system it was observed that the overall gas plus solids hold-up remains approximately constant until all the small gas bubbles are supplanted and then increased in direct relation to the solids volume. The k_La mirrored the gas hold-up trend and decreased with a fall in gas hold-up. In the salt solution k_La decreased in direct relationship to the solids concentration, to 40% of the no solids value at around 19% solids by volume of dispersion. Dynamic engagement and disengagement experiments established that the salt solution behaves differently than water with the small bubbles initially growing in size rather than being coalesced directly into the large bubble population.     

Lipase/acyltransferase‐catalysed interesterification of fat blends containing n‐3 polyunsaturated fatty acids

The lipase/acyltransferase from Candida parapsilosis is an original biocatalyst that preferentially catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. In this study, the performance of the immobilised biocatalyst in the interesterification in solvent‐free media of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA) was investigated. The interesterification activity of this biocatalyst at a water activity (a_w) of 0.97 was similar to that of commercial immobilised lipases at a_w values lower than 0.5. Thus, the biocatalyst was further used at an a_w of 0.97. Response surface modelling of interesterification was carried out as a function of medium formulation, reaction temperature (55–75 °C) and time (30–120 min). Reaction media were blends of palm stearin (PS), palm kernel oil and triacylglycerols (TAG) rich in n‐3 PUFA (“EPAX 4510TG”; EPAX AS, Norway). The best results in terms of decrease in solid fat content were observed for longer reaction time (>80 min), lower temperature (55–65 °C), higher “EPAX 4510TG” content and lower PS concentration. Reactions at higher temperature led to final interesterified fat blends with lower free fatty acid contents. TAG with high equivalent carbon number (ECN) were consumed while acylglycerols of lower ECN were produced.     

Effect of a Seaweed Extract on Fatty Acid Accumulation and Glycerol-3-Phosphate Dehydrogenase Activity in 3T3-L1 Adipocytes

This study was to determine the effect of a seaweed Ascophyllum nodosum extract (SE) containing 220 mg g⁻¹ phlorotannins on differentiation and fatty acid accumulation in differentiating 3T3-L1 adipocytes. 3T3-L1 cells (2 × 10⁴ mL⁻¹) were seeded to 24-well plates and proliferated to reach confluence and then were treated with media containing 0, 12.5, 25, 50, 75 and 100 μg mL⁻¹ SE for 8 days. Dexamethasone, methyl-isobutylxanthine and insulin (DMI) were added to the media in the first 2 days to induce cell differentiation. On day 8 the adipocytes were harvested for measuring cellular fatty acid concentration and the activity of glycerol-3-phosphate dehydrogenase (GPDH). It was found that treatment with SE increased (P < 0.01, n = 6) cellular myristoleic acid (C14:1), palmitoleic acid (C16:1) and oleic acid (C18:1) and total monounsaturated fatty acids (MUFA) without significantly affecting the cell number and saturated fatty acid (SFA). Ratios of MUFA/SFA, C14:1/C14:0, C16:1/C16:0 and C18:1/C18:0 in cellular lipids increased (P < 0.05, n = 6) with the SE treatment in a dose dependent manner (P < 0.001). Treatment with 75 μg mL⁻¹ SE depressed (P < 0.05) cellular GPDH activity. The results indicate that the biological factors in the SE may be involved in differentiation and MUFA accumulation in adipocytes.     

Stereocomplex formation between poly(L‐lactic acid) and poly(D‐lactic acid) with disproportionately low and high molecular weights from the melt

Poly(L ‐lactic acid) (PLLA) and poly(D ‐lactic acid) (PDLA) with very different weight‐average molecular weights (M_w) of 4.0 × 10³ and 7.0 × 10⁵ g mol^?1 (M_w(PDLA)/M_w(PLLA) = 175) were blended at different PDLA weight ratios (X_D = PDLA weight/blend weight) and their crystallization from the melt was investigated. The presence of low molecular weight PLLA facilitated the stereocomplexation and thereby lowered the cold crystallization temperature (T_cc) for non‐isothermal crystallization during heating and elevated the radial growth rate of spherulites (G) for isothermal crystallization, irrespective of X_D. The orientation of lamellae in the spherulites was higher for the neat PLLA, PDLA and an equimolar blend than for the non‐equimolar blends. It was found that the orientation of lamellae in the blends was maintained by the stereocomplex (SC) crystallites. Although the G values are expected to decrease with an increase in X_D or the content of high‐molecular‐weight PDLA with lower chain mobility compared with that of low‐molecular‐weight PLLA, G was highest at X_D = 0.5 where the maximum amount of SC crystallites was formed and the G values were very similar for X_D = 0.4 and X_D = 0.6 with the same enantiomeric excess. This means that the effect of SC crystallites overwhelmed that of chain mobility. The nucleating mechanisms of SC crystallites were identical for X_D = 0.1–0.5 in the T_c range 130–180 °C. Copyright © 2011 Society of Chemical Industry     

EFFECTS OF GLYCEROL ON THE DRYING OF GELATIN AND SUGAR SOLUTIONS

ABSTRACT

The water diffusion coefficients D of gelatin, sucrose arid maltodextrin solutions were determined from the isothermal drying (desorption) rates as a function of water content u ( 0.1 < u < 1.0 ) and temperature (303, 323K) for various glycerol contents ( W_G = 0 – 0.43 kg-glycerol/kg-total solid). When W_G was above 0.2, D increased especially at low water contents (u < 0.25). The desorption isotherms were measured for the same systems. The equilibrium water content at a given water activity A_w decreased with an increase in W_G when A_w < 0.5. This indicates that adding glycerol weakens the water-solute interaction especially at low water contents. Glycerol also softened gelatin films and resulted in loss possibilities of surface cracks during drying.     

Effect of structure of HEMA–DEGMA hydrogel matrix on diffusion coefficients of PEG tracers. Variation of hydrogel crosslink density by change of polymer concentration

Dependence of diffusion coefficients of spin-labeled poly(ethylene glycol)s (PEGs, M_w = 1500, 3000, and 6000) determined by One-Dimensional Electron Spin Resonance Imaging (1D ESRI) on the properties of hydrogel matrices prepared by photopolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(2′-hydroxyethoxy)ethyl methacrylate (DEGMA) was studied. The hydrogels were characterized by degree of crosslinking, ν_gel, by hydrodynamic correlation length, ξ_gel, and by self-diffusion coefficient of water, D_H2O. The tracer diffusion coefficients were analyzed in the frame of scaling reptation and hydrodynamic models. Molecular weight dependence of the tracer diffusion coefficients follow expression D  M_w^x with exponent x = −1.2 ± 0.1 which excludes contribution of reptation to the diffusion. Steep decrease of the tracer diffusion coefficients with increasing polymer concentration was observed. Decrease of the tracer diffusion coefficients with increasing ratio of the hydrodynamic radius of the tracer to the hydrodynamic correlation length of the hydrogel matrix, R_H/ξ_gel, was well fitted with predicted stretched exponential expression. Dependence of the tracer diffusion coefficients on the degree of crosslinking ν_gel suggested as a new scaling variable was found to closely follow empiric stretched exponential dependence in the whole ν_gel range studied.     

Facile synthesis of nanocrystalline hexagonal tungsten trioxide from metallic tungsten powder and hydrogen peroxide

A hexagonal form of tungsten trioxide (h‐WO₃, particle size: 15.9‐57.1 nm) was found to be formed by a direct reaction between metallic tungsten powder (W, particle size: 0.45‐0.59 μm) and 15%‐30% hydrogen peroxide (H₂O₂) aq solution. Oxide film on the powder surface having the similar crystal structure as h‐WO₃ was essential for the formation, and the surface oxide film was formed by aging the powder in air at 45°C, a relative humidity of 100% (P_H2O 96 hPa) for 3‐28 days or in ambient atmosphere at room temperature for 12 years. The Rietveld analysis performed in the space group P6₃/mcm (Z = 6) indicated the crystal structures were the same as those of the reported h‐WO₃ and that the crystallographic characteristic was as follows: a = 0.74219 nm, c = 0.77198 nm for h‐WO₃ from the 28‐day aged powder, and a = 0.74538 nm, c = 0.77194 nm for h‐WO₃ from the 12‐year aged powder.     

Morphology and structure of YSZ powders: Comparison between xerogel and aerogel

Yttria-stabilized zirconia (YSZ) fine powders were prepared via sol–gel route in order to shape thermal barrier coatings (TBCs) from these powders. The main objective is to develop new undirectional coatings to allow best thermo-mechanical accommodations compared to conventional processes. To reach this aim, powders have to be able first to be highly dispersed into a sol (non-agglomeration, high specific surface area, etc.) and second to crystallize in the required metastable phase t′. Two routes have been used to dry gels: the conventional way which consists of simple evaporation of the solvent is compared to drying in supercritical conditions. Both YSZ powders after calcination at 950 °C of xerogel (Ex-xero-YSZ powder) and aerogel (Ex-aero-YSZ powder) crystallize in the tetragonal form. N₂ adsorption/desorption analysis of the Ex-xero-YSZ powder indicates an S_w of 2.8 m²/g. For the Ex-aero-YSZ powder, the S_w (26 m²/g) is much higher than of Ex-xero-YSZ, leading to a better sintering capability. This high S_w is correlated to the small crystallite size (26 nm) and the alveolar morphology of Ex-aero-YSZ powders compared to Ex-xero-powder (49 nm). By reducing particles size and increasing the S_w of the powders, supercritical drying appears as a promising way to prepare stable slurries or loaded sols from fine YSZ particles for TBC applications. Indeed, after preparing nanometric powders, they are dispersed into a sol before shaping on superalloys substrates. After thermal treatment at 950 °C for 2 h which corresponds to the working temperature of TBC, the final aim will be to prepare ceramic YSZ coatings.     

Enhancement of both reaction yield and rate of synthesis of structured triacylglycerol containing eicosapentaenoic acid under vacuum with water activity control

Production of structured triacylglycerols (sTAG) containing eicosapentaenoic acid (EPA) at the sn-1 (or 3) position using Lipozyme in a solvent-free system was studied. Optimal water activity (a _w) for the synthesis of the sTAG was investigated. Vacuum was applied to shift reaction equilibrium toward the synthesis reaction by removing by-products. During vacuum application, the water level of the reaction system was controlled at the optimal level by addition of a suitable amount of water at a predetermined interval. Intermittent periodic addition of a suitable amount of water into the reaction mixture made the reaction rate faster than that without adding water. A molar yield of 89.7% of the targeted sTAG was obtained after 16 h reaction with a _w control during the vacuum application as compared with the yield of 87.0% after 24 h of reaction without a _w control during the vacuum application.     

Diffusion behaviour of selenite and hydroselenide in compacted bentonite

The apparent diffusivities (D_a) for selenium (Se) in compacted bentonite were obtained at a dry density of 1.6 mg/m³ as a function of silica sand content and temperature under reducing conditions, in which the dominant species of Se is predicted to be HSe⁻ (hydroselenide) and were compared with D_a values obtained under anaerobic conditions, in which the dominant species of Se is predicted to be SeO₃²⁻ (selenite). The experiments were carried out by an in-diffusion method and a Na bentonite, Kunigel-V1® with Na smectite content of 46–49 wt.%, was used in a series of diffusion experiments. All diffusion experiments were carried out in a controlled N₂ atmosphere glove box. The effects of silica sand content and temperature on D_a are altogether summarized as follows: (1) The D_a values show a tendency to increase with increasing silica sand content. (2) The D_a values show a tendency to increase with increasing temperature. (3) The increasing rate of D_a with temperature is approximately constant, independent of silica sand content. The D_a values for HSe⁻ are about one order of magnitude smaller than those for SeO₃²⁻. This trend is consistent with that of distribution coefficients obtained by batch method. The D_a values for HSe⁻ were well correlative with smectite partial density for both temperatures. This indicates that Se diffusion, including retardation processes, is predominantly controlled by the properties in part of smectite. The calculated activation energies for diffusion in the porewater [ΔE_a(porewater)] were in the range of 17.6–31.6 kJ/mol and were slightly higher than that of ionic diffusivity in free water [ΔE_{a(free water)}=15.3 kJ/mol] for HS⁻, which takes the same species as HSe⁻ in solution. Furthermore, the relative partial molar activation energies [ _(relative)] calculated from ΔE_{a(free water)} and ΔE_a(porewater) values were in the range of −16.2 to −2.2 kJ/mol. A reason might be that the properties of the porewater of compacted bentonite are different from that of free water.