DIRECT NUMERICAL SIMULATIONS OF THE DYNAMICS OF PARTICLES WITH ARBITRARY SHAPES IN SHEAR FLOWS

A fluid-structure interaction method based on the arbitrary Lagrangian-Eulerian method and a dynamic mesh method was developed to simulate the dynamics of a rigid particle in shear flows. In the method, the governing equations for the fluid flow and particle motion were sequentially solved in a two-way coupling fashion. The mesh system was deformed or re-meshed by the dynamic mesh method. The method was employed to simulate the dynamics of a single particle suspended in a flow channel and the dynamics of the particle were studied. The simulation results show that the angular velocity is not only a function of the inclination angle, is but also influenced by the aspect ratio yielding a hysteresis, while the angular velocity obtained from the Keller-Scalak model is a function only of the inclination angle and does not show a hysteresis. The present simulations clearly demonstrate that the Fluid-Structure Interaction (FSI) module is very stable, accurate and robust.     

EFFECTS OF EXTRUSION CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF A MUTANT RICE CULTIVAR,GOAMI2 – HIGH IN NONDIGESTIBLE CARBOHYDRATES

ABSTRACT

A mutant rice Goami2, a cultivar high in nondigestible carbohydrates (NDCs), was extrusion‐cooked at feed moisture (20, 25%), screw speed (200, 300 rpm) and barrel temperature (110, 120 and 130C). Effects of extrusion conditions on the physical and functional properties were investigated. NDCs were determined by total dietary fiber (TDF) and resistant starch (RS) contents. Increasing moisture resulted in an increment of density, water absorption index (WAI) and hardness, and a decrement in expansion and water solubility index (WSI). A higher barrel temperature decreased the hardness and increased the WSI probably due to a higher proportion of gelatinized starch. Extrusion caused a reduction in TDF in the extrudates, as well as a significant decrease in RS contents. However, extrudates processed at moisture (%), screw speed (rpm) and barrel temperature (C) combinations of 25/200/110 and 25/200/120 showed no significant difference in TDF contents compared with its raw rice. Multiple regression models showed that feed moisture had the most pronounced effect on extrudate qualities, followed by barrel temperature and screw speed.

PRACTICAL APPLICATIONS

Rice, being one of the primary dietary sources of carbohydrates worldwide, is the major energy and nutritional sources. In recent years, demands have been increasing for rice with a wide range of value‐added properties, such as enhanced nutrient, aroma, color and rice kernel shape, including functional properties. Goami2 is a mutant rice of Ilpumbyeo, a high japonica rice cultivar, and has been revealed to have higher nondigestible fractions. However, Goami2 rice has unsuitable properties for traditional cooking because of the difficulty of gelatinization, which might result in a hard texture of cooked rice compared with that of ordinary rice. On the basis of its nutritional and functional benefits, exploiting the possible utilization of Goami2 for processed food products would increase the potential consumption of Goami2 for various food products.     

Effects of Electrical Stimulation and Hot Boning on Functional Characteristics of Preblended Beef Muscle in Model Systems

Thirty beef carcasses were used to determine the effects of electrical stimulation (ES) and hot boning on the emulsifying capacity (EC) and thermal emulsion stability (TES) of preblended Triceps brachii (TB) muscle (long head) from sides assigned to one of four treatments: (1) conventionally boned after chilling at 2–8°C until 48 hr postmortem (CB); (2) hot boned at 1 hr postmortem (HB); (3) ES during bleeding and conventionally boned at 48 hr postmortem (ESCB); and (4) ES during bleeding and hot boned at 1 hr postmortem (ESHB). HB preblended samples had greater EC and TES values than CB preblended samples in both nonstimulated (P < 0.05) and stimulated carcasses. When compared to nonstimulated sides, ES decreased (P < 0.05) these values in both ESHB and ESCB sides.     

Improving Detection of Vibrio vulnificus in Octopus variabilis by PCR

PCR methods can detect foodborne pathogenic bacteria with simplicity, specificity and speed. In order to improve sensitivity and speed of PCR methods for detection of Vibrio vulnificus in small octopus homogenate, several media and culture conditions were compared. Modified brain heart infusion media containing 2% NaCl and adjusted to pH 8.0 and 30°C was most effective for enrichment of the bacteria. Procedures affecting the efficiency of template DNA extraction and target DNA amplification were also optimized. By these combined efforts, a PCR procedure capable of detecting V. vulnificus as low as 10 cells/mL within 10h was developed.     

EVALUATION OF A CHEMICAL MARKER FOR PROCESS LETHALITY MEASUREMENT AT HOC IN A CONTINUOUS FLOW HOLDING TUBE

Meat beads containing glucose precursor of a chemical marker and alginate beads containing spores of Bacillus stearothermophilus were prepared and subjected to steam heating at HOC for selected time intervals. Marker yields were related to spore survivor data and lethality values obtained from time-temperature data to generate calibration curves. Meat balls, fabricated with meat (marker precursor) and alginate (microbial spores) beads placed at the center, were heated at 110 ± 0.5C for selected time intervals (0–55 min) in a continuous flow holding tube. During the heat treatment, the panicles were held stationary in the holding tube while the carrier fluid (0.5% CMC solution) was circulated at 2.6 gallons per min. Transient time-temperature responses of the particles were recorded at bead locations during test runs. All treated samples were analyzed for marker yield as well as spore survivors. Using the calibration curves and marker yield data under test conditions, the corresponding spore count reduction and accumulated lethalities were computed. Lethalities and spore count reductions calculated from marker yield data showed good correlations with those obtained from the experiment. The results indicate that the chemical marker has good potential to provide data on accumulated lethality and spore count reductions. Prior to extension of this approach to aseptic processing conditions, additional kinetic data on spore destruction and marker formation should be gathered at temperatures applicable to these processes.     

Enzymatic Browning Control in Minimally Processed Mushrooms

Treatments to control discoloration of minimally processed mushrooms were investigated. Whole or sliced mushrooms were immersed in browning inhibitor solutions and evaluated for color change during storage. Browning was more intense in first break mushrooms than in second, and in unwashed mushrooms compared to washed. However, washing sometimes induced purple discolorations, associated with bacterial lesions. Other discolorations were induced by hypochlorite, 4-hexylresor-cinol, and acidic dips. The most effective treatment was a combination of sodium erythorbate, cysteine, and EDTA at pH 5.5. Addition of preservatives to browning inhibitor dips did not improve storage life. However, dipping in 5% hydrogen peroxide prior to application of browning inhibitors significantly increased shelf-life.     

Densification process of TiCx–Ni composites formed by self-propagating high-temperature synthesis reaction

Densification behaviour of the TiC-Ni system formed by self-propagating high-temperature synthesis (SHS) were studied to develop the structural metal-matrix composites. The composites were prepared by two routes: (1) consolidation during the SHS reaction, and (2) consolidation process after the SHS reaction. The final phases of the stoichiometric reactant mixture of titanium and graphite with 50 wt% nickel produced by simultaneous combustion reactions, were titanium carbide in a nickel-rich solid solution containing carbon and titanium. The density of the products was relatively low, with a value of 90% theoretical density. In the second approach, liquid infiltration and liquid-phase sintering were applied for the titanium carbide-nickel mixture. Densification rates were reduced due to the excess carbon in the combustion products of titanium carbide. The densities of the liquid-phase sintered samples were more than 97% theoretical density. This revised version was published online in November 2006 with corrections to the Cover Date.     

高电力二极管Nd：YAG激光器的最佳共振条件

对高电力二级管Nd:YAG激光器的输出功率和偏光特性进行图表分析.介绍了平行-评判共振器的结构,讨论了根据偏光方向的热焦点和热弹性产生的热效果问题.在原有的输出功率下,能保持稳定的激光输出的最佳共振条件,同时对非对称构成的高电力Nd:YAG激光共振器在理论上预测的光共振条件和实验结果进行了比较.