Shoji Koide

Electrohydrodynamic drying characteristics of wheat using high voltage electrostatic field

The drying characteristics of wheat treated by a high voltage electrostatic field (HVEF) were investigated in this study. The drying rate of wheat in a HVEF was significantly higher than that of a control for various drying temperatures and electric field strengths. A Multiple points-to-plate corona discharge electrode of HVEF improved the average drying rate by 2.1, 2.0, and 1.7 respectively for 10, 7.5, and 5 kV/cm electric field strength compared with the values of the corresponding air-dried control samples. Drying enhancement by a HVEF at lower drying temperature was more marked than that at higher temperature. The drying rate increased when the voltage increased and the discharge gap decreased. The power consumption was very small with the current of a few microamperes. A regression model to describe the drying characteristics of wheat treated by a HVEF was developed.

Compressive strength properties of rough rice considering variation of contact area

Abstract Compressive strength properties of three different varieties of rice, namely Akitakomachi (Short grain variety), Delta and L201 (Long grain varieties) were determined in their natural state. Rough rice was compressed between two rigid plates using a stress–strain tester and the force–deformation curves recorded. Determinations made included initial yield point, yield point, initial yield stress and strain, Youngs modulus and Poissons ratio. Stress was determined by considering the variation of contact area with compression force whereas Poissons ratio was computed based on the Boussinesqs theory. Initial yield force and Youngs modulus were found to be about 18 N and 543 MPa, respectively for the three varieties of rice. Initial yield point and yield point occurred after almost the same deformation of about 0.16 and 0.60 mm, respectively. However, short grain rice had higher Poissons ratio and lower yield stress compared to long grain rice. Consideration of variation in contact area during compression gave representative apparent compressive strength properties for rough rice.

Thin-layer Drying of Maitake Mushroom analysed with a Simplified Model

Abstract The drying of Maitake mushroom ( Grifola frondosa ), which has a high initial moisture content, was analysed using the modified plate drying model. This consists of three parameters; surface mass transfer coefficient H , dynamic equilibrium moisture content M e , and drying constant K . The model was simplified by presenting an approximate function expression for the plate drying model and can be used to simulate the drying process for Maitake mushroom. Samples were dried at various air temperatures (35, 40, 45, 50 and 55°C) and relative humidities (30, 40, 50, 60 and 70%). Results indicated that the modified plate drying model used to predict the moisture content and drying rate fitted reasonably well with experimental results for the different drying conditions. Both the drying constant K and surface mass transfer coefficient H of the modified plate drying model were expressed as Arrhenius-type functions of temperature.

Respiration and climacteric patterns of apples treated with continuous and intermittent direct current electric field

Abstract Negative corona discharge and parallel plate electrode configurations were used to investigate the efficacy of intermittent and continuous electric field treatment in retardation of respiration and suppression of climacteric peak in apples ( Malus domestica Borkh, c.v. Fuji, Sansa, Starking Delicious and Golden Delicious) post-harvest. Direct current electric field was generated by a 50 Hz alternating current supply. The electrodes were kept 8 cm apart. Climacteric peak CO 2 evolution in apples stored at 0, 10 and 23 °C were affected by high electric field treatment. Treatment of apples in high electric field suppressed CO 2 evolution at climacteric peak. Both treatments in a uniform field of parallel aluminum plate electrode and a negative corona discharge field retarded respiration in apples. Further, the direction of electric field using the parallel aluminum plate electrode influenced apple respiration.

Improvement of polyphenol extraction from grape skin by pulse electric field

Effects of a treatment of grape peels with pulsed discharges under water at applied voltage from 30 to 60 kV on the evolution of total polyphenols in Kyoho grape processing was investigated using a six-stage Blumlein-line pulsed power generator. The grape peels were sunk in diluted water and the pulse voltage was applied to five needle electrodes set into the water. The experimental results showed that the permeabilization of the grape peels by application of the pulsed discharges at room temperature caused an increase of total polyphenols with respect to the control during the process. The total polyphenols increased from 2.5 to 4.78 µmM gallic acid eq. /100g with increasing applied voltage from 30 to 60 kV at 5 pps (pulses per second). The increase rates of the total polyphenols by applying pulse voltage were obtained to be 16.7% at 30 kV, and 84.2% at 60 kV applied voltage. A microscopic measurement clearly showed that red color pigments were extracted from anthocyanoplasts into the cells through an electroporation process.

Decomposition of Ethylene Using Dual-Polarity Pulsed Dielectric Barrier Discharge

Ethylene (C2H4) gas promotes the aging of some kinds of fruits and vegetables such as persimmon, banana, and cucumber. Decomposition of ethylene using nonthermal plasma is effective for keeping freshness of fruits and vegetables in the transportation container. The ethylene was decomposed into gas stream using a dielectric barrier discharge (DBD) reactor driven by dual-polarity pulse generator that consisted of four insulated gate bipolar transistors and a pulse transformer. The output voltage of the pulse generator was 10 kV in amplitude, 1 kilopulse/s in repetition rate, and 50 μs in rectangular pulsewidth. The 200 ppm ethylene was diluted with dried air and was employed as simulated gas of the transportation container. The gas mixture was fed into the DBD reactor for the evaluation of the decomposition efficiency. The ethylene concentration decreased to less than 1 ppm after the DBD treatment at 30 J/L in input energy. The energy efficiency for ethylene decomposition was around 50 g/kWh and was almost independent of the initial ethylene concentration. The decomposition efficiency increased with increasing oxygen content of the background gas. The byproducts were analyzed by a Fourier transform infrared spectrometer. The results showed that the H2O and CO2 were mainly produced after the decomposition of the ethylene by the DBD plasma.

Influence of oxygen concentration on ethylene removal using dielectric barrier discharge

Ethylene gas is decomposed using a dielectric barrier discharge plasma reactor for long-period preservation of fruits and vegetables. The oxygen concentration in ambient gas is varied from 2 to 20% to simulate the fruit and vegetable transport container. The experimental results show that the efficiency of ethylene gas decomposition increases with decreasing oxygen concentration. The reactions of ethylene molecules with ozone are analyzed by Fourier transform infrared spectrometry. The analysis results show that the oxidization process by ozone is later than that by oxygen atoms. The amount of oxygen atoms that contribute to ethylene removal increases with decreasing oxygen concentration because the reaction between oxygen radicals and oxygen molecules is suppressed at low oxygen concentrations. Ozone is completely removed and the energy efficiency of C2H4 removal is increased using manganese dioxide as a catalyst.

Simultaneous Estimation and Modeling of Thermophysical Properties of Big-Eyed Tuna and Pacific Cod

The thermophysical properties (thermal conductivity, thermal diffusivity, and specific heat) of big-eyed tuna and pacific cod were measured at various temperatures (5–50°C) by the modified version of current probe method. The optimal prediction models for these thermophysical properties were determined. The random model was applied to predict the thermal conductivity of seafood in a wide range of temperature and it provided the accurate predictions for the samples. The thermal diffusivities of the samples could be predicted by Martens’s equation. An additive relationship exists between the specific heat of the sample, the composition, and the specific heat of each component.