Physicochemical properties, kinetics and thermodynamic studies of polyphenol oxidase from sorghum (Sorghum bicolor (L.) Moench) for potential use in industry

Advances Polyphenol Oxidase (PPO) from Sorghum bicolor (white and yellow varieties) grains were investigated for optimum processing condition. The partially purified enzyme was obtained from two varieties of Sorghum bicolor by step-wise separation through ion-exchange and size-exclusion chromatography. The final purification gave a yield of 7.33 % and 12.3 % for PPO from white and yellow sorghum respectively. The PPO has Vmax and Km of 2.66 U.mL−1 and 19.72 mM for white sorghum, 1.33 U.mL−1 and 12.92 mM for yellow sorghum. The optimal pH of PPO activity was found at pH 4 and pH 7 for white and pH 4 and pH 8 for yellow sorghum. The pKa 7.4 and 8.7 were obtained for PPO from white sorghum, and pKa 5.4, 7.4 and 8.5 for yellow sorghum. The PPO residual activity were above 70 % at 5 hours of incubation within the neutral pH ranges for white sorghum, while those of yellow sorghum were below 40 %. The optimum temperature of 40 ºC and 30 ºC for white and yellow sorghum PPO respectively. The average value of enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) obtained at 20 min of incubation and temperature 50 – 80 °C were respectively 49.03 kJ.mol−1, - 129.52 J.mol−1.K−1, and 92.81 kJ.mol−1 for white sorghum PPO, and 90.1 kJ.mol−1, - 9.29 J.mol−1.K−1, and 93.37 kJ.mol−1 for yellow sorghum PPO. Zn2+, Fe2+ and ascorbic acid inhibited PPO while Cu2+, Na+ and K+ activated the enzyme. The results suggest the processing parameters for controlling PPO in potential industrial application of white and yellow sorghum grains.

Investigation on laser welding of Ti-6Al-4V plates in corner joint

The article deals with laser beam welding of Ti-6Al-4V plates for aerospace applications. A number of trials are conducted to weld 3-mm-thick plates in corner joint configuration; a specific device for clamping and shielding to prevent oxidation is used. Autogenous welding is investigated, the joint being accessed from the outside, as a butt-welded corner joint. Referring to international standards, the results are first discussed in terms of geometry of the welding bead in the cross-section since titanium alloys are reported to be notch sensitive. Moreover, microstructure and microhardness are investigated. An optimum processing condition is suggested in order to perform laser beam welding with minimal undercut and porosity.

Experimental Study of Glass Ceramics from Liquid Hematite Slag

Much slag occupied the land resources and caused severe damage to the ecological environment. A lot of work has been done on the reclaimation and utilization of slag. The composition, type and characteristics of slag were similar in some way to glass ceramics, which are architectural decoration materials or wearable and corrosion-proof materials with high quality and low price. In this paper, glass ceramics was prepared using hematite slag, which has not been cooled down in order to save energy. The optimum processing condition determined by orthogenesis test to prepare glass ceramics was hematite78.16%, CaF23.91%, CaO7.77%, coke10.16%.The smelting temperature is 1550 for 60 min and the crystallization time is 90 min. Microstructure analysis was studied by SEM. The microcrystalline structure was many petals, which was diopside crystal proved by X-ray analysis.

Optimized Processing Condition for a Photocrosslinkable Stable Nonlinear Optical Polymer

ABSTRACTThe optimum processing condition for a photocrosslinking Nonlinear Optical(NLO) polymeric system was established. Parameters such as change in heat capacity at glass transition temperature, rate of decrease of absorbance of residual uncrosslinked chromophores, and measurement of mass loss upon heating were used to set up the optimum condition. Poly(vinyl cinnamate) was used as the photocrosslinkable polymer and 3- cinnamoyloxy-4-[4-(N, N-diethylamino)-2-cinnamoyloxy phenyl azo] nitrobenzene was used as the NLO molecule. Poling at 70°C for 5 minutes followed by photocrosslinking with a dose of 2.5 mW/cm 2 for 10 minutes results in a stable second order nonlinear optical material.

Optimasi Proses Pembuatan Mi Sorgum Dengan Menggunakan Ekstruder Ulir Ganda (Optimization of Sorghum Noodle Processing with Twin Screw Extruder)

The objective of this research was to optimize the sorghum noodle processing with two variables i.e. extruder temperature (80, 85, 90oC) and screw speed (10, 15, 20 Hz). The optimum process was chosen by using Response Surface Methodology (RSM), based on 2 parameters, i.e. cooking loss and elongation. The result of this research showed that the optimum processing condition with desirability of 0.736, was resulted from the combination of the extruder temperature of 85oC and screw speed of 20 Hz. The verification showed that the sorghum noodles from this optimum condition had cooking loss of 11.87 %, and elongation of 234.84. Keywords: noodle, sorghum, optimization, twin screw extruder, RSM