Heating process of soybean using hot-air and superheated-steam fluidized-bed dryers

The present work investigated drying characteristics and inactivation of urease in soybean dried by superheated-steam and hot-air fluidized beds. The value of effective diffusion coefficient, which was determined by a method of slopes, was increased with increased drying temperature and increased moisture content. Furthermore, it depended on the type of heating medium, with higher moisture diffusion for soybean dried by hot air. Inactivation of the urease enzyme in both media showed difference in rate, in which the enzymatic inactivation was faster for soybean dried in superheated steam than in hot air. For the individual heating medium, the modified first-order reaction was adequately fitted to experimental data. The rate of inactivation was found to increase as the temperature and moisture content were increased. The urease enzyme was inactivated, along with maintaining protein solubility and lysine content being in standard range, as soybean was treated at a temperature between 135 and 150 °C for the hot air and the treatment temperature could be reduced to be lower than 135 °C by using superheated steam.     

Improvement in the remaining activity of freeze-dried xanthine oxidase with the addition of a disaccharide–polymer mixture

In order to improve the remaining activity of a practically important freeze-dried enzyme, xanthine oxidase (XOD), the effects of disaccharide (sucrose and trehalose), polymer (bovine serum albumin: BSA and dextran) and a mixture of them on the loss of XOD activity during freeze-drying and subsequent storage were investigated. All samples were amorphous solids and their glass transition temperatures (T_g) were evaluated by using differential scanning calorimetry. Although dextran showed no stabilizing effect on the freeze-dried XOD, the others protected XOD from the activity loss during freeze-drying to a certain extent. It was found that the mixture of disaccharide (sucrose or trehalose) and BSA improved the XOD activity synergistically. The XOD activity of the samples decreased gradually during storage at a temperature range of between 25 and 60 °C. Samples stored at temperatures below the T_g showed a lower loss of XOD activity than those stored at just the T_g.     

Material Formulations for AR/PMMA and AR-TiO2/PMMA Blends and Effects of UV Radiation and Tio2 Loading on Mechanical and Antibacterial Performances

Polymer blends of poly(methyl methacrylate)(PMMA) and acrylic rubber(AR) were manufactured with the addition of titanium dioxide (TiO₂). TiO₂ was initially added to the AR phase in AR/PMMA blends. The impact strength of PMMA improved with AR loading. The addition of TiO₂ appeared to decrease the tensile properties of the blends with AR of 10-30?wt% of AR, but increased with AR of 40-50?wt%, this being related to distribution level of TiO₂. UV radiation deteriorated the overall mechanical properties, where TiO₂ could retain the properties. To achieve acceptable antibacterial performance, AR loadings of 40 and 50?wt% in AR-TiO₂/PMMA blends are recommended, together with TiO₂ loadings of 1.5?pph and 0.5?pph, respectively.     

High Dielectric Permittivity and Maxwell–Wagner Polarization in Magnetic Ni0.5Cu0.3Zn0.2Fe2O4 Ceramics

Nanocrystalline Ni_0.5Cu_0.3Zn_0.2Fe₂O₄ (NCZFO) powder was fabricated by a modified sol?Cgel method and then the compacted powder of NCZFO was sintered at 950, 1000, and 1100?^°C for 6 h. The dielectric and electrical properties of sintered samples were investigated as functions of frequency and temperature. All of the NCZFO samples exhibit the high dielectric response behavior and show the Debye-like relaxation, which is attributed to the Maxwell?CWagner polarization and thermally activated mechanisms. The impedance spectroscopy analysis reveals that the NCZFO ceramics are electrically heterogeneous. The sintering temperature has significant influence on the dielectric dispersion behavior of the NCZFO samples, which should be mainly attributed to the large variation of the grain conduction activation energies.     

Stabilizing effects of sucrose–polymer formulations on the activities of freeze-dried enzyme mixtures of alkaline phosphatase,nucleoside phosphorylase and xanthine oxidase

To stabilize two freeze-dried enzyme mixtures, consisting of alkaline phosphatase, nucleoside phosphorylase and xanthine oxidase, the effects of sucrose–polymer (bovine serum albumin, gelatin, dextran, polyethylene glycol and polyvinylpyrrolidone) formulations on the remaining activity of the enzyme mixtures were investigated. The enzyme mixtures were freeze-dried with the additives, and then stored at 25, 40 and 55 °C. The glass transition temperatures (T_g) of the freeze-dried samples were assessed in order to determine their physical stability. The T_g values of sucrose–polymer formulations, with the exception of sucrose–polyethylene glycol, were higher than that of sucrose alone. Comparison of the remaining activities of freeze-dried samples showed that sucrose–bovine serum albumin and/or –gelatin prevented activity loss more effectively than did sucrose. Sucrose–polyethylene glycol showed protective ability equivalent to that of sucrose. On the other hand, sucrose–dextran and/or –polyvinylpyrrolidone diminished the stabilizing effect of sucrose. During storage, sucrose–gelatin prevented gradual activity loss to a much greater degree than did sucrose alone.     

A comparison of scheduling algorithms for flexible flow shop problems with unrelated parallel machines,setup times,and dual criteria

This paper considers a flexible flow shop scheduling problem, where at least one production stage is made up of unrelated parallel machines. Moreover, sequence- and machine-dependent setup times are given. The objective is to find a schedule that minimizes a convex sum of makespan and the number of tardy jobs in a static flexible flow shop environment. For this problem, a 0–1 mixed integer program is formulated. The problem is, however, a combinatorial optimization problem which is too difficult to be solved optimally for large problem sizes, and hence heuristics are used to obtain good solutions in a reasonable time. The proposed constructive heuristics for sequencing the jobs start with the generation of the representatives of the operating time for each operation. Then some dispatching rules and flow shop makespan heuristics are developed. To improve the solutions obtained by the constructive algorithms, fast polynomial heuristic improvement algorithms based on shift moves and pairwise interchanges of jobs are applied. In addition, metaheuristics are suggested, namely simulated annealing (SA), tabu search (TS) and genetic algorithms. The basic parameters of each metaheuristic are briefly discussed in this paper. The performance of the heuristics is compared relative to each other on a set of test problems with up to 50 jobs and 20 stages and with an optimal solution for small-size problems. We have found that among the constructive algorithms the insertion-based approach is superior to the others, whereas the proposed SA algorithms are better than TS and genetic algorithms among the iterative metaheuristic algorithms.     

Effect of vanadium pentoxide on the mechanical,thermal, and electrical properties of poly(vinyl alcohol)/vanadium pentoxide nanocomposites

In this study, we examined the effect of vanadium pentoxide (V₂O₅) on the mechanical, thermal, and morphological properties of poly(vinyl alcohol) (PVA)/V₂O₅ nanocomposites. The PVA/V₂O₅ nanocomposites were prepared by solution mixing, followed by film casting. The results show that the Young's moduli of the resulting nanocomposites films were higher than the pure PVA modulus with increasing V₂O₅ content, and it reached a maximum point at about 0.4 wt % V₂O₅ content at 8.55 GPa. The tensile strength and stress at break increased with increasing V₂O₅ content. The addition of V₂O₅ did not affect the melting temperature. The crystallization temperatures of PVA were significantly changed with increasing V₂O₅ content. The 5% weight loss degradation temperature of the nanocomposites was measured by thermogravimetric analysis. The degradation temperatures of the V₂O₅ nanocomposites increased with increasing filler content and were higher than the degradation temperature of pure PVA; this showed a lower thermal stability compared to those of the nanocomposites. The results show that the thermal stability increased with the incorporation of V₂O₅ nanoparticles. The dielectric constant of PVA had a tendency to improve when the dispersion of particles was effective. The morphology of the surfaces the nanocomposites was examined by scanning electron microscopy. We observed that the dispersion of the V₂O₅ nanoparticles was relatively good; only few aggregations existed after the addition of the V₂O₅ nanoparticles at greater than 0.4 wt %. In perspective, the addition of 0.4 wt % V₂O₅ nanoparticles into PVA maximized the mechanical, thermal, and electrical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effective Diffusivity and Kinetics of Urease Inactivation and Color Change During Processing of Soybeans with Superheated-Steam Fluidized Bed

Influences of temperature and moisture content on diffusional transport property and kinetics of both urease inactivation and color change during soybean treatment with superheated steam in the temperatures of 120-150°C were investigated. The experimental results have shown that the effective diffusivity and apparent rates of such reactions are related to temperature in a way that the rates of water transport, urease inactivation, and brown pigment formation are higher with higher temperature. In addition, these rates are also enhanced by increasing moisture content, except for the browning reaction that is inhibited by this factor due to the dilution effect. The reduction in urease activity is reasonably described by modified first-order reaction and the color change of soybeans is characterized by three Hunter parameters in which the changes of L-, a- and b-values are followed according to zero-order, modified Monod and first-order reactions, respectively. The kinetics of inactivation and color change, along with the experimental data of protein solubility and lysine content, have been suggested that the soybean should be treated with superheated steam at the temperature ranging from 120 to 135°C. The superheated-steam fluidized-bed technique can simultaneously be applied for both drying and inactivating such components in soybeans by a single operation when the initial moisture content falls within a suitable range, approximately lower than 20%d.b. At elevated initial moisture contents, two-stage drying technique is recommended in order to avoid excessive cooked soybeans.     

Improvement in impact resistance of polylactic acid by masticated and compatibilized natural rubber

Mastication is the technique widely used to reduce viscosity of natural rubber and the higher mastication speed leads to lower NR viscosity. The optimum viscosity of NR that could provide high impact strength for the blends depends largely on the blending time and method. This study is focused on the enhancement of impact strength of polylactic acid (PLA) blended with masticated natural rubber (NR) using sorbitan ester (SE), a biodegradable food additive, as a compatibilizer. The effects of NR mastication, compatibilizer and NR contents and the mixture’s viscosity on the morphological, thermal and impact properties of PLA/NR blends were investigated in relation to the changes in the morphology, thermal properties and impact strength of PLA/NR blends. It was found that the optimum viscosity of NR that provided the highest impact strength to the blends was achieved when NR was masticated at 40 rpm for 15 min. The highest impact strength corresponded well not only with the small NR phase size, but also with the highest crystallization rate. For the effect of compatibilizer, it was found that a small amount of SE could more than double the impact strength of the blends, where the optimum compatibilizer content was 0.5 wt%. Interestingly, the high impact strength of the blends in all cases was accompanied by short interparticle distance and slightly higher percent crystallinity.