EFFECT OF PHYSICAL PROPERTIES OF FOOD PARTICLES ON THE DEGREE OF GRAININESS PERCEIVED IN THE MOUTH

Nineteen food materials were pulverized and passed through standard sieves to prepare samples with different particle sizes (23–500 μm). Each sample was tested for physical properties, and sensory evaluation tests were conducted to obtain the graininess threshold value and the degree of graininess discrimination. The graininess threshold value tended to decrease and the degree of graininess discrimination tended to increase with increasing degree of circularity, with decreasing solubility, with decreasing water absorption rate- particle size coefficient, and with increasing WK₂/K₁. The degree of graininess discrimination tended to increase with increasing particle size and increasing WK₂. With a multiple-regression analysis, the graininess threshold value was expressed by six physical properties, and the degree of graininess discrimination was expressed by eight physical properties, each with high contribution rates.     

A Commutation Overlap Period Reduction Method Expanding the Buck Operating Range for a Bidirectional Isolated DC–DC Converter

This paper proposes a bidirectional isolated DC–DC converter with an active clamp circuit and two novel control methods in the buck mode. A circulating current reduction method decreases the conduction loss. A commutation overlap period reduction method maintains the output power by expanding the maximum actual duty cycle even if the input voltage decreases. The experimental results show that the proposed method increased the maximum output 1.5 times, without increasing the voltage applied to the low‐voltage side MOSFETs under the minimum input voltage condition. A 2‐kW class prototype showed a higher than 90% efficiency over a wide operating range for a greater than 20 input–output voltage ratio at 100‐kHz switching frequency.     

Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Proteinaceous surfactants were prepared by applying the “one-step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n-alkyl esters of L-leucine as lipophiles. Each of the hydrophile-lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone-1M carbonate (pH 9) containing 2 mM 2-mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L-leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low-molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C₄–C₆ alkyl esters of leucine showed greater whippability, whereas the incorporation of the C₁₀–C₁₂ alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.     

Properties and Structure of Lithium Borate and Strontium Borate Glasses

Experimental results for some physical properties of Li₂O-B₂O₃ and SrO-B₂O₃ glasses with high modifier content showed anomalies in the composition dependence of many properties such as thermal expansion coefficient, transformation temperature, softening temperature, density, and refractive index at 30 to 33 mol% modifier oxide in these glasses. These anomalies are attributed to the formation of nonbridging oxygens near this composition.     

表面粗糙度引起的超声波厚度测量误差的修正方法

根据对未经平整的粗糙锈蚀表面分别进行超声波厚度测量和机械测量的比较试验，发现超声波测量的平均误差为0．6～2．2mm。为解决该问题，建议使用一种表面回波持续时间的误差修正法，并选用合适的2．25MHz宽带换能器进行测量。该方法也适用于喷漆的表面检查。     

A Conceptual Design Study for the Error Field Correction Coil Power Supply in JT-60SA

This paper describes a conceptual design study for the circuit configuration of the Error Field Correction Coil (EFCC) power supply (PS) to maximize the expected performance with reasonable cost in JT-60SA.The EFCC consists of eighteen sector coils installed inside the vacuum vessel,six in the toroidal direction and three in the poloidal direction,each one rated for 30kA-turn.As a result,star point connection is proposed for each group of six EFCC coils installed cyclically in the toroidal direction for decoupling with poloidal field coils.In addition,a six phase inverter which is capable of controlling each phase current was chosen as PS topology to ensure higher flexibility of operation with reasonable cost.     

ORAL PERCEPTION OF GRITTINESS: EFFECT OF PARTICLE SIZE AND CONCENTRATION OF THE DISPERSED PARTICLES AND THE DISPERSION MEDIUM

The perceptibility of grittiness and the threshold value of grittiness were examined in five disperse model systems: aqueous suspensions, low and high viscous suspensions, and soft and hard gels. Fourteen types of microcrystalline cellulose were used having different particle sizes (between 6–79 μm) and physical properties (shape, degree of polymerization, and state at the material stage). In each system, the proportion of people who perceived grittiness increased with increasing particle size and decreased with increasing particle concentration demonstrating that perception of grittiness depended on both particle size and concentration. The proportion of people who perceived grittiness was found by multiple regression analysis to have a high correlation with the logarithm of (particle size × concentration). Each system gave an approximate regression equation representing this relation. The value of particle size × concentration at the grittiness threshold was defined as the point where 50% of people perceived grittiness. These values were calculated to be 6.0 (aqueous suspension). 19.7 (low viscosity), 26.7 (high viscosity suspension), 30.7 (soft), and 42.1 (hard gel). The factor contributing most to grittiness was concentration, followed by dispersion medium and particle size. The proportion of people who perceived grittiness was also expressed by a multiple regression equation which included these three factors. The obtained results suggest the possibility of predicting and controlling grittiness in foods.     

Determination of Tetrodotoxin by Capillary Isotachophoresis

A method is described for the quantification of tetrodotoxin (TTX) in crude extracts of puffer fish by capillary isotachophoresis. Conditions for isotachophoresis consisted of a leading electrolyte of 5 mM potassium acetate, pH 6.0, containing 0.2% Triton X-100 and 0.5 vol of dioxane, and a terminating electrolyte of 10 mM β-alanine adjusted to pH 4.5 with acetic acid. It was possible to quantify the TTX content of crude unfractionated puffer extracts, and obtain values similar to those obtained by mouse bioassays which are time consume.     

Transformation of Yttria-Doped Tetragonal ZrO2 Polycrystals by Annealing in Water

Phase changes and the microstructure resulting from low-temperature annealing of yttria-doped tetragonal ZrO₂ polycrystals in water were investigated at 65° to 120°C. Tetragonal ZrO₂ on the surface of the sintered body transformed to the monoclinic phase, accompanied by microcracking. The transformation rate in water, which was much greater than that in air, was first order with respect to surface concentration of tetragonal ZrO₂. Nonaqueous solvents with a molecular structure containing a lone-pair electron orbital opposite a proton donor site also greatly enhanced the transformation.