Extraction and application of antioxidants from black glutinous rice

This research aimed to determine optimum extraction condition of black glutinous rice crude extract and to determine its application as an antioxidant in fish oil enriched mayonnaise. Black glutinous rice flour was extracted twice with 70:30 acetone-water mixture (v/v) at pH 2 and 6.8 for 2, 4 and 8 h of total extraction times. Total phenolic content (TPC), total monomeric anthocyanin content (TMA) and antioxidant activities as determined by ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity assays of the crude extracts were measured. The extraction with pH 6.8 solvent for 4 h yielded the crude extract with significantly highest antioxidant activities analyzed by both FRAP and DPPH tests (p ≤ 0.05) although its TPC and TMA were not greatest. The freeze-dried extract from this condition was then added into fish oil enriched mayonnaise at 500 mg/kg and 1000 mg/kg (oil weight basis). Conjugated diene hydroperoxides (CDH), thiobarbituric acid reactive substance (TBARs) and color in CIELAB system of the mayonnaise samples stored at 30 °C were determined up to 30 days. The samples contained 1000 mg/kg crude extract had lowest rate of CDH and TBARs increase but had greatest extent of color deterioration, possibly due to anthocyanin degradation and Maillard reaction.     

The construction of robust mixture‐process experimental designs via genetic algorithm

Mixture experiments with the presence of process variables are commonly encountered in the manufacturing industry. The experimenter who plans to conduct mixture experiments in which a process involves the combination of machines, methods, and other resources will try to find condition of design factors which make the product/process insensitive or robust to the variability transmitted into the response variable. We propose the genetic algorithm (GA) for generating robust mixture‐process experimental designs involving control and noise variables. When the noise variables, which are extremely difficult to control or not routinely controlled during the manufacturing process and may change without warning, are considered in a mixture experiment, we propose the robust design setting. When considering a robust design, the design that has a lower and flatter faction of design space curves for all levels of the controllable process variables at varying noise interaction is preferable. We evaluate the designs with respect to these criteria for both the mean model and the slope model. The evaluation demonstrates that the proposed GA designs are robust to the contribution of the interactions involving the noise variables.     

Effect of processing parameters on the vulcanisation of natural rubber using glutaraldehyde

The process ability of vulcanising natural rubber using glutaraldehyde at low temperature has been studied. The main objective of this work is to improve the properties and stability of natural rubber (NR) using glutaraldehyde as a curing agent. In this study, the vulcanised samples were prepared systematically and compared with sulphur cured natural rubber vulcanisates. The influence of mole ratio of ammonia and glutaraldehyde, and the processing parameters (i.e. curing time and temperature) was investigated. The cured NR based on glutaraldehyde exhibited better hardness and thermal properties than that of the NR cured from conventional sulphur system. The experimental results reveal that the properties of glutaraldehyde cured NR can be developed with the proper additives combination and conditions adopted in the preparation. This cured system is very interesting due to it can be used for high temperature industrial applications. Moreover, it eases of processing at low temperature and cost.     

Fibroblast interaction with carboxymethylchitosan-based hydrogels

The interaction between L929 cells and carboxymethylchitosan (CM-chitosan)-based hydrogels, hydrogels from pure CM-chitosan and its blends, was examined in this study. Cytotoxicity of all materials was also assessed. The cellular morphology and behavior on the surfaces of the hydrogels were observed by scanning electron microscopy (SEM). The effects of various parameters, e.g., type and content of blended polymers, surface structure of hydrogels, and steaming condition used for the preparation of the hydrogels, on the cell-material response were investigated. The results of the cytotoxicity test revealed that all hydrogels were non-cytotoxic. The SEM micrographs demonstrated that the cells proliferated and spread onto a porous CM-chitosan sample. Better cell spreading was found on a flat surface of a CM-chitosan film. Rounded cells were observed when poly(vinyl alcohol) (PVA) was incorporated into CM-chitosan. Fewer cells were found when the content of PVA increased. Spherical clusters of the aggregated cells existed in the blends with ultra high viscosity carboxymethylcellulose (CM-cellulose). In contrast, with the use of low viscosity CM-cellulose, the cells appeared more spreading. The attached cells on the CM-chitosan film steamed at the highest temperature and longest period appeared to spread the most among all tested steaming conditions.     

Enhancement of recombinant soluble dengue virus 2 envelope domain III protein production in Escherichia coli trxB and gor double mutant

The dengue virus is currently the most important flavivirus causing human diseases in the tropical and subtropical regions of the world. The envelope protein domain III of dengue virus type 2 (D2EIII), which induces protective and neutralizing antibodies, was expressed as an N-terminal fusion to a hexa-histidine tag in Escherichia coli. The expression of recombinant D2EIII of 103 amino acids in the soluble form can be achieved using suitable host strains, such as Origami, at a low induction temperature of 18 degrees C. The enhanced production of the soluble protein could be attributed to the thioredoxin reductase (trxB) and glutathione reductase (gor) double mutations in the Origami genome. The soluble and refolded D2EIII proteins were recognized by different antibodies including human patient antiserum. The immunization of rats with soluble D2EIII protein elicited the production of antibodies that could recognize the D2EIII protein in the D2EIII precursor protein and in C-terminal truncated dengue envelope protein type 1-4. Thus, this protein production system is suitable for the production of authentic recombinant dengue proteins that may be used in the diagnosis of the dengue virus infection or in vaccine development.     

Outdoor atmospheric corrosion of carbon steel and weathering steel exposed to the tropical-coastal climate of Thailand

This study focuses on atmospheric corrosion of carbon steel and weathering steel exposed at two different locations with dissimilar meteorological parameters and airborne pollutants in Thailand. The samples are subjected to an outdoor atmosphere for up to 36 months at Rayong, close to the Gulf of Thailand, and Phangnga, near the Andaman Sea. Thickness loss (µm), corrosion rate (µm/year) together with corrosion product morphology and composition are systematically analyzed using X-ray diffraction and a scanning electron microscope. Corrosion resistance of the tested steels exposed at both locations is discussed based on the above-mentioned parameters and calculated corrosion kinetics. The results indicate that the total time of wetness, amount of rainfall and chloride deposition rate play an important role in corrosion behavior of the tested steels. Alloying elements, copper, chromium and nickel, are shown to improve corrosion resistance of the samples when exposed at the location with a higher chloride concentration.     

In vitro comparative hemostatic studies of chitin,chitosan, and their derivatives

The effects of chitin, chitosan, and their derivatives on in vitro human blood coagulation and platelet activation were comparatively studied. The coagulation was assessed by the measure of the whole blood clotting time (WHBCT) and plasma recalcification time (PRT). The tested materials were chitin, chitosan, partially N‐acetylated chitosan (PNAC), N,O‐carboxymethylchitosan (NOCC), N‐sulfated chitosan, N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride, and SPONGOSTAN® standard (a positive control). The results revealed that the WHBCTs of whole blood mixed with chitin, chitosan, NOCC, or SPONGOSTAN® standard were significantly decreased with respect to that of the pure whole blood (a blank control) (P < 0.05), while the WHBCT value of whole blood mixed with PNAC was not significantly reduced. However, the presence of PNAC significantly lowered the PRT value, similar to the addition of chitin, NOCC, or SPONGOSTAN® standard. Chitosan was found to reduce PRT, but not significantly. In the platelet adhesion and activation studies, the morphology of platelets adherent to the film surfaces of tested materials was examined using a scanning electron microscopic technique. Because of their effective coagulation activites, chitosan, PNAC, and NOCC were further evaluated to determine how platelets behaved when in contact with these film samples for given periods. It was found that NOCC activated platelets most effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 445–451, 2006     

Synthesis of acrylamide/acrylic acid‐based aluminum flocculant for dye reduction and textile wastewater treatment

Aluminum hydroxide‐poly[acrylamide‐co‐(acrylic acid)], AHAMAA, was synthesized with a redox initiator by solution polymerization in which the effects of reactant contents were optimized. The effects of pH, temperature, and initial dye concentration on Congo red reduction were investigated. A mixture of Congo red and direct blue 71, and the composite textile dye wastewater were investigated. Adsorptions of both dyes were more effective in the nonbuffered solution than those in the buffered solution, and Congo red adsorbed more than direct blue 71 at all pHs. The adsorption of Congo red increased with increasing temperature and its initial concentration. Both dyes obeyed the Freundlich adsorption isotherm. The maximum adsorptions in 100 mg dm^?3 solution were 109 ± 0.5 mg g^?1 and 62 ± 6.6 mg g^?1 for Congo red and direct blue 71, respectively. At 150 mg dm^?3 of the mixed Congo red and direct blue 71, the adsorption was 142 ± 2 mg g^?1 by 643 ± 3 mg dm^?3 AHAMAA. The 40 mg g^?1 dyes of the textile effluent wastewater were adsorbed by 500 mg dm^?3 AHAMAA. AHAMAA could decrease turbidity of the composite wastewater containing a mixture of reactive and direct dyes from 405 to 23 NTU. POLYM. ENG. SCI., 50:1535–1546, 2010. © 2010 Society of Plastics Engineers     

Influence of functional groups on properties of styrene grafted NR using glutaraldehyde as curing agent

Natural rubber grafted polystyrene (NR‐g‐PS) and natural rubber grafted polystyrene‐co‐methyl methacrylate (NR‐g‐P(S‐co‐MMA)) were prepared by emulsion polymerization technique using tert‐BuHP‐TEPA as a redox initiator to improve the thermal and mechanical stability of NR. Additional peaks appear in the Fourier‐transform infrared spectra at 695 and 1,732 cm^?1 confirms the formation of graft polymerization. The existence of functional groups on the grafted NR was also clearly confirmed from the morphology obtained from transmission electron microscopy analysis. The effect of curing on the mechanical and thermal properties of grafted NR has also been studied. Glutaraldehyde was used as the curing agent for the grafted and ungrafted NRs throughout the entire course of investigation. It was found that curing of grafted NR samples enhanced tensile strength, modulus, hardness, and thermal stability. Grafted NR showed the tensile strength values of 12 and 17 MPa for NR‐g‐PS and NR‐g‐P(S‐co‐MMA), respectively. Enhancement in thermal stability of NR was confirmend from the activation energy of degradation calculated based on thermogravimetric analyzer. The value of activation energy for NR (135.13 kJ/mol) was found to be increased to 147.89 kJ/mol (NR‐g‐PS) and 151.6 kJ/mol (NR‐g‐P(S‐co‐MMA)). The overall properties of NR have been strongly affected by the interaction and chain bundling between functional groups present in the grafted copolymer and the unsaturated chains in its structure. J. VINYL ADDIT. TECHNOL., 25:339–346, 2019. © 2019 Society of Plastics Engineers