Subcritical water extraction of phenolic compounds from pomegranate (Punica granatum L.) seed residues and investigation into their antioxidant activities with HPLC–ABTS+ assay

Subcritical water extraction (SWE) of phenolic compounds from pomegranate seed residues (PSR) was performed. Total phenolic content (TPC) and antioxidant capacities of the extracts obtained at different temperatures were determined, and the individual antioxidant capacities were evaluated by coupling high performance liquid chromatography with ABTS radical reaction system (HPLC–ABTS⁺). The results showed that the optimum extraction time was 30 min, solid to water ratio was 1:40, and the highest TPC was obtained at 220 °C. The effect of extraction temperature on TPC was significant (p < 0.05), and TPC ranged from 651.7 to 4854.7 (mg/100 g DW) between 100 °C and 220 °C. HPLC–ABTS⁺ profiles revealed that nine compounds had antioxidant activity. Furthermore, the formation of Maillard reaction products during SWE was investigated, and the content of 5-hydroxymethylfurfural (5-HMF) was determined. The comparative study indicated that SWE was a promising technique for preparation of PSR phenolics.     

Solubility and diffusivity of CO2 in carboxylated polyesters

The solubility of CO₂ in saturated polyester resins at different temperatures (306 and 343 K) and pressures (0.1-30 MPa) has been measured using a magnetic suspension balance. The solubility data were used for estimating the binary diffusion coefficients. The results show a good solubility of CO₂ in polymers, up to 0.64 g CO₂/g polymer. The diffusion coefficients of supercritical CO₂ in polymers have generally high values and are in the range from 0.156 × 10⁻⁸ to 10.38 × 10⁻⁸ cm²/s. DSC and XRD analyses of the semi-crystalline polymer samples indicate that amorphous degree of polymers after exposure to CO₂ is increased. The observed structural effects are dependent on pressure, temperature and time of exposure to CO₂.     

Flexible replication technique for high-aspect-ratio nanostructures

A flexible, nondestructive, and cost-effective replication technique for nanostructures is presented. The advantages of the process are: 1) it allows for tailoring structural parameters of the replica (e.g., line width) nearly independent of the structural geometry of the master; 2) it allows for replication of high-aspect-ratio structures also in polymer materials from solution (especially noncurable polymers) such as polystyrene and polymethylmethacrylate; 3) it includes an easy separation process, thus preserving the master for repeated use. Linear grating replicas with line widths ranging from 88 to 300 nm are obtained using a single nanostructured master. Nanofibers and complex nanopatterned replicas are achievable. The presented technique and its flexibility show that atomic layer deposition is a unique tool for the preparation of high-efficiency polarizer diffractive optics, photonics, electronics, and catalysts.     

Changes in the content of fructans and arabinoxylans during baking processes of leavened and unleavened breads

Fructans and arabinoxylans (AXs) are prebiotics naturally occurring in cereal grains which have well-known beneficial effects on human health. However, the majority of grains consumed by humans are processed prior to the consumption. The effect of baking on fructan and AX levels has been studied in rye breads, but there is a scarcity of data on the presence of fructans and AXs in wheat breads. Therefore, the aim of this study was to investigate the effect of baking on stability of fructans and total AXs in breads made from both wheat and rye flours. Bread loaves were baked using an automatic bread maker Breville BBM100 (Sydney, Australia). Sugar analysis was performed using high-performance liquid chromatography on a Dionex ICS-3000 unit. This study showed slight loss of total AXs (6–10 %) during preparation processes of leavened, yeast-free and unleavened breads. In contrast, there was 40–60 % degradation in fructan content of leavened, but no significant losses of fructans in unleavened breads. Yeast-free breads had higher contents of both fructans and AXs than leavened breads. Generally, smaller changes in the content of these prebiotics were apparent in wholemeal and rye than in white breads. It seems that differences in the structures of AXs and fructans in cereals, and the presence of yeast play significant role in determining stabilities of these components during baking.     

Enzymatic synthesis of oleyl oleate in dense fluids

Esterification between oleic acid and oleyl alcohol, catalyzed by theMucor miehei immobilized lipase in a batch-stirred tank reactor with supercritical carbon dioxide as solvent produced higher reaction rates at supercritical conditions than in the solvent-free system. A continuous fixed-bed reactor was designed based on the results obtained from batch experiments. At 150 bar, 40°C, and with water activity 0.46% w/w, the activity of the enzyme preparation is practically unchanged when CO₂ was used as solvent. The addition of small amounts of water increases the conversion rate. The higher conversion also was observed at longer residence time. Whenn-butane was used as reaction medium, a decrease in conversion was observed.     

Synthesis of Oleyl Oleate with Immobilized Lipase from Mucor miehei

The synthesis of oleyl oleate with immobilized 1,3-specific lipase from Mucor miehei is presented in this article. Oleyl alcohol was esterified with oleic acid in the presence of a Mucor miehei lipase (lipozyme^IM) to obtain oleyl oleate. The effects of various temperatures and various enzyme/substrate ratios have been investigated to determine optimal conditions for the esterification process. The highest conversion of oleic acid 86.9 % was obtained at 50°C. The optimal addition of lipase to substrates was determined to be 0.1 g per gram of reaction mixture. The esterification can be modeled successfully as a reverse second-order reaction. Thermodynamic properties of the reaction system at 50°C were also determined. Activation energy was 14.65 kJ/mol, entropy of activation –0.8 J/mol·K and free energy of activation was 98.568 kJ/mol.     

Kinetics of supercritical carbon dioxide extraction of borage and evening primrose seed oil

In the present work, high‐pressure extraction of borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) seed oil, containing the valuable γ‐linolenic acid (GLA), has been investigated. Extraction was performed with supercritical carbon dioxide on a semi‐continuous flow apparatus at pressures of 200 and 300 bar, and at temperatures of 40 and 60 °C. A constant flow rate of carbon dioxide in the range from 0.17 to 0.20 kg/h was maintained during extraction. The extraction yields obtained using dense CO₂ were similar to those obtained with conventional extraction using hexane as solvent. The composition of extracted crude oil was determined by GC analysis. The best results were obtained at 300 bar and 40 °C for both seed types extracted, where the quality of oil was highest with regard to GLA content. The evening primrose seed oil extracted with supercritical fluid extraction was particularly rich in unsaturated fatty acids: up to 89.7 wt‐% of total free fatty acids in the oil. The dynamic behavior of the extraction runs was analyzed using two mathematical models for describing the constant rate period and the subsequent falling rate period. Based on the experimental data, external mass transfer coefficients, diffusion coefficients and diffusivity in solid phase were estimated. Results showed good agreement between calculated and experimental data.     

Copper nanowires within the central channel of tobacco mosaic virus particles

Simple electrochemical deposition techniques can produce highly defined metal nanostructures in templates. Electroless deposition (ELD) can be effectively used for depositing metals on insulators such as biological or plastic surfaces. With biomolecular templates, metallization methods are often restricted to mild reductions, and the deposition of copper at pH values above 12 is usually not applicable. We produced copper nanowires of 3 nm in diameter and up to 150 nm in length by electroless deposition within the 4 nm wide channel of tobacco mosaic virus (TMV) particles. We employed a low pH (7.5) copper electroless deposition solution that is compatible with biomolecules. The fabrication process of the nanowires is based on sensitization of tobacco mosaic virus with Pd(II) prior to the electroless deposition. We analyzed the chemical composition of the nanowires by energy-filtering transmission electron microscopy, and used the method also for nickel and cobalt nanowires deposited within the viral channel.