Effect of the mixing rate on the morphology and photocatalytic activity of ZnO powders prepared by a precipitation method

The urchin-like shape of ZnO powders was prepared by mixing of Zn²⁺ and NaOH solutions at various mixing rates. In this work, ε-Zn(OH)₂ was the first precipitant that was subsequently transformed to ZnO in the alkaline medium during heating. The size of the urchin-like shape of the ZnO powder decreased with a decrease of the mixing rate. The large urchin-like shape also had a large diameter of its hexagonal facet (0 0 0 1) and showed the highest photocatalytic degradative activity on methylene blue.     

Rheological characterizations of texturized whey protein concentrate-based powders produced by reactive supercritical fluid extrusion

A powder blend comprising (by weight) 94% whey protein concentrate (WPC80), 6% pre-gelatinized corn starch, 0.6% CaCl₂, and 0.6% NaCl was texturized using a supercritical fluid extrusion (SCFX) process. The blend was extruded at 90 °C in a pH range of 2.89 to 8.16 with 1% (db) supercritical carbon dioxide (SC-CO₂) and 60% moisture content. The texturized WPC-based (TWPC) samples were dried, grounded into powder, reconstituted in water, and evaluated using a range of rheological studies. Most TWPC samples exhibited shear thinning behavior and their mechanical spectra were typical of weak gel characteristics. The TWPC produced under extremely acidic condition of pH 2.89 with SC-CO₂ yielded the highest η^* (10,049 Pa s) and G′ (9,885 Pa) compared to the unprocessed WPC (η^* = 0.083 Pa s and G’ = 0.036 Pa). The SCFX process rendered WPC into a product with cold-setting gel characteristics that may be suitable for use as a food texturizer over a wide range of temperatures.     

Comparing phenanthrene degradation by alginate‐encapsulated and free Pseudomonas sp. UG14Lr cells in heavy metal contaminated soils

BACKGROUND: Many polycyclic aromatic hydrocarbon (PAH) contaminated sites also contain high levels of toxic heavy metals. The presence of heavy metals can adversely affect PAH biodegradation. Encapsulation of bacterial cells has been shown to improve survival and activity of cells under various environmental stresses. This study examined if encapsulation of a phenanthrene‐mineralizing bacterial strain could improve its survival and phenanthrene degradation in heavy metal contaminated soils. RESULTS: Alginate encapsulation did not improve survival and phenanthrene degradation by Pseudomonas sp. UG14Lr in heavy metal contaminated soil. Phenanthrene degradation by, and survival of, free cells and alginate‐encapsulated cells were similar in soil contaminated with 5 mg kg^?1 dry soil of As, Cd, or Pb. The number of UG14Lr cells decreased to undetectable level when the concentration of each heavy metal was increased to 100 mg kg^?1 dry soil. UG14Lr, when inoculated as free cells, survived the best and they were detected over 60 days of incubation in soil. Cells in both wet and dry alginate beads survived less well than free cells at the higher metal concentrations. Correspondingly, phenanthrene degradation in soil inoculated with free UG14Lr was better than that in soil inoculated with alginate‐encapsulated cells. CONCLUSION: Alginate encapsulation adversely affected the survival and phenanthrene degradation ability of UG14Lr cells in heavy metal contaminated soil. It is postulated that alginate may have concentrated the metals which in turn increased the toxicity to UG14Lr cells. The results are of interest to those interested in the use of encapsulation technology to formulate microbial cells for bioremediation purposes. Copyright © 2009 Society of Chemical Industry     

Bilateral Comparison of Blackbodies for Clinical Infrared Ear Thermometers between NIMT and NMIJ

This article describes the results of the bilateral comparison of blackbodies for infrared ear thermometers (IRETs) between the National Institute of Metrology (Thailand), NIMT, and the National Metrology Institute of Japan (NMIJ). The purpose of this comparison was to ensure consistency of the national radiance temperature scales for IRETs maintained by NIMT and NMIJ. Results of the measurements indicate differences in radiance temperature within 10 mK with a maximum measurement uncertainty of 64 mK. The equivalence of the radiance temperature scales realized by both NIMT and NMIJ in the range of 35  \(^{\circ }\) C to 42  \(^{\circ }\) C for IRET calibration is indicated. The results of this bilateral comparison can be used in terms of quality assurance and validation of calibration.     

Emulsification mechanisms and characterizations of cold, gel-like emulsions produced from texturized whey protein concentrate

A novel supercritical fluid extrusion (SCFX) process was used to successfully texturize whey protein concentrate (WPC) into a product with cold-setting gel characteristics that was stable over a wide range of temperature. It was further hypothesized that incorporation of texturized WPC (tWPC) within an aqueous phase could improve emulsion stability and enhance the rheological properties of cold, gel-like emulsions. The emulsifying activity and emulsion stability indices of tWPC and its ability to prevent coalescence of oil-in-water (o/w) emulsions were evaluated and compared with the commercial WPC80. The cold, gel-like emulsions were prepared at different oil fractions (φ = 0.20–0.80) by mixing oil with the 20% (w/w) tWPC dispersion at 25 °C and evaluated using a range of rheological techniques. Microscopic structure of cold, gel-like emulsions was also observed by Confocal Laser Scanning Microscope (CLSM). The results revealed that the tWPC showed excellent emulsifying properties compared to the commercial WPC in slowing down emulsion breaking mechanisms such as creaming and coalescence. Very stable with finely dispersed fat droplets, and homogeneous o/w gel-like emulsions could be produced. Steady shear viscosity and complex viscosity were well correlated using the generalized Cox–Merz rule. Emulsions with higher viscosity and elasticity were obtained by raising the oil fraction. Only 4% (w/w) tWPC was needed to emulsify 80% (w/w) oil with long-term storage stability. The emulsion products showed a higher thermal stability upon heating to 85 °C and could be used as an alternative to concentrated o/w emulsions and in food formulations containing heat-sensitive ingredients.     

Persistence of maternal milk derived Lactobacillus plantarum in the infant feces and its antagonistic activity against Escherichia coli O157:H7

Food Science and Biotechnology - The diversity of lactic acid bacteria (LAB) in maternal milk and feces from Thai mother-infants pairs were revealed through nested PCR-DGGE. LAB species residing in...     

Physicochemical changes in whey protein concentrate texturized by reactive supercritical fluid extrusion

The mechanisms of interactions in whey protein concentrate (WPC) texturized by reactive supercritical fluid extrusion and pH modifications were evaluated in terms of protein solubility in different extraction buffers, electrophoresis, free sulfhydryl (SH) groups, and apparent viscosity. The soluble protein content and free SH groups of the texturized WPC (tWPC) produced at pH 2.89 decreased by 20% and 16% relative to the unextruded control. It was completely soluble in the presence of urea and SDS, indicating the importance of non-covalent interactions in maintaining the structure of this product. Its dispersion (20% w/w) yielded a creamy texture with a particle size in the micron-range (mean diameter 5 μm) and contributed 258 times higher viscosity compared to the unextruded control. The tWPC produced at pH 8.16 was soluble only in the presence of a reducing agent. It yielded a grainy texture with a high proportion of large particles due to an extensive aggregation via intermolecular disulfide formations.     

Properties of yeast free bread produced by supercritical fluid extrusion (SCFX) and vacuum baking

A novel technology, supercritical fluid extrusion (SCFX), allows for continuous production of yeast-free dough leavened via incorporation of supercritical carbon dioxide (SC-CO₂). In this study, an optimum dough formulation, SCFX leavened dough production and baking procedures were developed. A premixed dough was leavened by 1% (feed basis) SC-CO₂ injection in a twin screw extruder at 37 °C. Specific mechanical energy input was 18 kW h/ton. SCFX leavened dough and bread density, moisture content, bake loss, texture profile analysis (TPA) and stress relaxation were evaluated and compared to conventional yeast leavened breads throughout 5-day storage. A combination of vacuum and conventional baking yielded the lowest SCFX leavened bread density of 0.19 g/cm³ and crumb hardness comparable to conventional yeast leavened and commercial products. This approach could be beneficial for a continuous production of consistent ready-to-bake dough and breads having equivalent quality to commercial products but produced in shorter time and without ethanol emission issues.

Industrial relevance

The dough leavening process in conventional bread production is an industrial hurdle for a number of reasons. First, it is very time consuming. Dough leavening through yeast fermentation can take up to eight hours, which is not conducive to high production rates. This long waiting period also means a great deal of storage space is required to produce a large amount of dough. This storage environment must be carefully controlled in terms of temperature, humidity, and air conditions in order to maintain optimal yeast fermentation, which can also be very costly. Finally, the emission of ethanol, a significant byproduct of yeast fermentation, must be controlled according to the EPA clean air act. Expensive catalytic converters must be installed and maintained in commercial bread production facilities.Bread produced by super critical fluid extrusion (SCFX) overcomes these problems. Total dough production time is less than an hour, and with the proper baking equipment, the entire process can be made continuous. This means constant output, less downtime, and none of the costly storage space used for conventional dough proofing. Furthermore, since there is no yeast being used, there is no ethanol being produced. This means no harmful volatile organic emissions and no expensive catalytic converter. Coupled with vacuum baking, this process results in bread with qualities similar to commercially produced bread in significantly less time.