Yasuhiko Shiinoki

On-line monitoring of moisture and salt contents by the microwave transmission method in a continuous salted butter-making process

The microwave transmission technique was applied to simultaneously monitor the moisture and salt contents in a butter-making process. The dielectric properties of a salted water-in-oil (W/O) emulsion as a model of salted butter was investigated. The dielectric loss tangent, tanδ, of a non-salted W/O emulsion was independent of the volume fraction of the dispersed phase, whereas that of the salted W/O emulsion increased with increasing volume fraction of the dispersed phase below a frequency of 3 GHz. It was theoretically confirmed that the moisture and salt contents of the salted W/O emulsion could be evaluated from the linear formula for phase shift and attenuation in the same frequency region, and that the electrolyte had more effect on attenuation than the phase shift. The moisture and salt contents of salted butter could be simultaneously monitored in the butter-making process by means of a linear regression formula for the phase shift and attenuation at a frequency of 3 GHz in a concentration range between 15.5 and 17.5% by weight, and between 1.0 and 2.0% by weight, respectively.

Freezing injury of cultured rice cells analyzed by dielectric measurement

Abstract The permittivity of a rice (Oryza sativa L. japonica)-cell suspension was measured in the frequency range from 0.2 to 20 MHz. A good linear correlation (=r) of 0.999 was observed between the permittivity at 0.41 MHz and the cell density. Permittivity was lost as a result of cell destruction by aging, ultrasonication, or boiling. From a comparison between changes in the permittivity of the cell suspension and freezing curves obtained by differential scanning calorimetry, the major freezing injury was believed to be due to damage to the plasma membrane. Freezing damage was measured by the intact cell ratio calculated from the permittivity and 2,3,5-triphenyltetrazolium chloride (TTC) reduction viability assay under various freezing conditions. The effects of changes in the concentration of dimethylsulfoxide used as a cryoprotectant and in the cooling rate showed similar trends for the intact cell ratio and TTC viability, although there was a quantitative discrepancy between them.

Viscoelastic behavior of an agar—gelatin mixture gel as a function of its composition

Abstract The stress relaxation behavior of an agar—gelatin mixture gel was analyzed as a function of the stress relaxation behaviors of the component agar and gelatin gels. A six-element model composed of three components of the Maxwell mechanical model was applicable for each stress relaxation behavior. Except for the behavior of the shortest relaxation time, the three elastic moduli of the mixture gel, including the instantaneous elastic modulus, became predictable from the corresponding moduli of the agar and the gelatin gels, taking into account the concentration dependence and using a parallel-series combination model for the elasticity. The viscosities of the mixture gel were also predictable from the corresponding viscosities of the component agar and gelatin gels, except for the behavior of the shortest relaxation time.

Finite-element analysis on the effective thermal conductivity of dispersed systems of spheres of various sizes

Abstract A three-dimensional finite-element model was used to analyse the effective thermal conductivity of dispersed systems of spheres of various sizes, and the results were compared with several known models. Among the known models considered, the Maxwell-Eucken model was shown to give a fairly good approximation for the effective thermal conductivity when the dispersed spheres were arrayed in a simple cubic lattice and a body-centred cubic lattice over a range of thermal-conductivity ratios of the spheres and the continuous phase, which varied between 0.01 and 100. The applicability of the Maxwell-Eucken model suggested by the finite-element analysis was confirmed by experimental measurements for gels in which solid paraffin particles or liquid paraffin droplets were dispersed.

Instantaneous elastic deformation of a porous gel analysed by the finite element method

Abstract The three-dimensional stress relaxation theories and a two-dimensional finite element computation were used to analyse the instantaneous elastic deformation of a compressible porous agar-gelatin gel. Poissons ratio for the porous gel was predicted successfully over an experimental range of porosity up to 0·3 by the finite element computation, but the combinations of the known theories were applicable only in a narrow range of very low porosity. Substituting the predicted values of Poissons ratio into Okanos equation for concentrated dispersions, the experimental instantaneous longitudinal elasticity of the porous gel was predicted successfully. Then the shear modulus and the bulk modulus of the porous gel could be predicted. Elastic deformation of an incompressible oilimpregnated gel was also analysed for comparison.

Mid-Infrared Spectroscopic Determination of Sugar Contents in Culture Media

Abstract A simple, rapid and accurate method for determining sugar contents in culture media by mid-infrared spectroscopy was developed using a Fourier transform infrared spectrometer equipped with an attenuated total reflectance accessory by focusing our attention on sugar consumption by plant cells. In addition, we performed lactic acid fermentation under the different conditions of the media and the starter concentration to examine this measuring method. Consequently, this study represents an important step in the development of nonintensive on-line monitoring devices for bioreactors and of simple, rapid and accurate analysis of the cellular metabolism through the composition changes in media.

Suppression of Cell Metabolism by Structuring Water under Hydrophobic-Gas Pressure.

疎水性ガスを細胞内水に溶解させ, 水を構造化させる新しい細胞の代謝抑制方法を提案した.そして, 栄養成分が含まれていない細菌懸濁液に疎水性ガスを溶解させて保存実験をおこない, すべての供試ガス (キセノン, クリプトン, アルゴン, ヘリウム) において, 細菌の死滅抑制効果が認められた.また, 細菌の種類により死滅抑制効果に差異が生じ, 細胞壁の厚いグラム陽性菌に対する死滅抑制効果よりも, 細胞壁の薄いグラム陰性菌に対する死滅抑制効果のほうが大きかった.一方, キセノンガスを用いた場合, 死滅抑制効果は他のガスを用いた場合よりも顕著であった.また, 本研究の実験範囲では, キセノンガスを用いた場合のみ死滅抑制に最適な初期分圧の存在が観察された.この最適キセノンガス分圧においては, 細菌の代謝をほぼ完全に抑制できる最適な水の構造をとることが実験的に示唆された.

Measurement of Fluid Thermal Conductivity with a Steady State Hot Wire Method

Thermal conductivity measurement apparatus was developed based on the steady state hot wire method. The measurement cell was made up of coaxial stainless cylinders and a stainless sheathed hot probe. The results of numerical analysis suggested that the effect of convection heat transfer was negligible small when the clearance between the outer cylinder and the hot probe was less than 0.75mm. The average deviation of the measured thermal conductivity from known values was about 2 %. Thermal conductivity of skim milk, W/O and O/W emulsions were measured with the apparatus. The results indicated that this method is applicable to the measurement of each total solid content of skim milk, water or oil content of emulsions.

An Extended Hot-Wire Method for Monitoring Fluid Viscosity and the Onset of Gel Formation

The practical feasibility of a hot-wire method for monitoring the change in viscosity and gel-setting point of fluids was critically examined on the basis of the theoretical relationship for free-convection heat transfer around a circular cylinder. By comparing the temperature of a hot-wire probe placed in a gelatin solution and in whole blood, this method is proved to be extremely effective for assessing coagulation.