Yasuhisa Seo

Discrimination of odors emanating from ‘La France’ pear by semi-conducting polymer sensors

Abstract Odors emanating from ‘La France’ pears were examined by the electronic odor detection system based on the adsorption on to and subsequent desorption of volatile compounds from an array of semi-conducting polymers, a so-called electronic nose. ‘La France’ pears were grouped in three storage treatments after being harvested. The first group was the pears stored for 115 days at 277 K, the second and third groups were the pears ripened in a chamber at 303 K for 1 and 5 days, respectively, after the storage of 115 days at 277 K. The physiological states of pears in the three treatments were thought to be different. Pears of the first group were judged to be immature, those of the second group were mature, and those of the third group were over mature. Gas chromatography separation of volatile compounds emanating from ‘La France’ pear resulted in seven peaks representing acetaldehyde, ethanol, methyl acetate, ethyl acetate, butanol, butyl acetate and hexyl acetate. Odors from pears were detected by the sensor array with 32 different polymers. The odors were classified into three classes dependent on their physiological states through distinctive odor pattern formed by 32 outputs. It was observed that there was the strong relationship between the results obtained by headspace GC and the electronic nose.

Concentration of liquid foods by the use of gas hydrate

Abstract The formation of gas hydrate in both distilled water and coffee solutions was studied to provide the basic data for the development of liquid foods concentration by the use of gas hydrate. Experiments were carried out with xenon gas. Coffee solution samples were prepared to the concentration of 1.5, 5.1, 9.9 and 14.7 wt.%. Temperature was set from 2°C to 10°C and the range of xenon pressure was from 0.20 to 1.00 MPa. It was found that xenon hydrate could form in coffee solutions. The time required for xenon hydrate formation in coffee solutions, that is induction time, depended on the concentration of solution. Longer induction time was required for higher concentration of solution. The growth of xenon hydrate was examined through the change in size distribution of xenon hydrate with time. The effect of temperature on the size of xenon hydrate was clearly observed at the temperature–pressure condition that showed low xenon solubility. Finally, lower xenon pressure and higher temperature created the larger size of xenon hydrate crystals but it required longer time.

Measurement of Evaporation Coefficient of Water During Vacuum Cooling of Lettuce

Experimental investigations had been carried out to measure the evaporation coefficient of water from lettuce undergoing vacuum cooling, applying an evaporation boundary-layer model developed for the free surface of pure liquids. The value of evaporation coefficient for lettuce was found to be dependent on mass flux from the leaf surface, and about 4 times lower than that for the free surface of water. The effects of operating pressure to the coefficient were not appeared definitely under the experimental conditions.

Odor Recognition of Soy Sauce by Semiconducting Polymer Sensors

In order to recognize the odor of soy sauce, an electronic nose having 32 different semiconducting polymers was used. Prior to the odor analysis of soy sauce, the effect of water vapor in a sample gas on the change in resistance of a sensor was examined using two kinds of spray-dried coffee that exhibited different odors. The effect of the water vapor was eliminated by controlling the humidity of the reference air during baseline determination. Two dark soy sauces produced by different companies were used. The electronic nose recognized the difference in the odors of the soy sauces, of which point mappings formed clusters of odor apart from each other. The change in odor with time caused by exposure to air was also detected.

Separation Process of Nonpolar Gas Hydrate in Food Solution under High Pressure Apparatus

Separation process of nonpolar gas hydrate formation in liquid food was experimentally studied under high pressure container. Xenon (Xe) gas was selected as hydrate forming gas and coffee solution was used as a sample of liquid food. The high-pressure stainless steel container having the inner diameter of 60 mm and the volume of 700 mL with a U-shaped stirrer was designed to carry out this experiment. A temperature of 9.0°C and Xe partial pressure of 0.9 MPa were set as a given condition. The experiment was designed to examine the effect of steel screen size, formation rate, temperature condition, and amount of Xe gas dissolving in the solution on the separation process which was indicated by concentration efficiency. Screen size of 200 and 280 mesh resulted in higher concentration efficiency than that of 100 mesh. The higher stirring rate caused the higher formation rate of Xe hydrate and created the smaller Xe hydrate crystals. At the condition giving the same solubility in water, temperature of 14.8°C resulted in lower concentration efficiency than 9.0°C. The increase in the amount of Xe gas dissolving in coffee solution caused the concentration efficiency to decrease; however, the concentration ratio between the final and initial concentration of the solution increased.

CONTROL OF THE STATE OF INTRACELLULAR WATER FOR HIGH QUALITY STORAGE

Abstract When xenon gas dissolves into water, the formation of a hydrophobic hydration will occur and the water becomes structured. The creation of structured water was confirmed by proton N.M.R. measurement. The metabolism is expected to be suppressed if the intracellular water structured by being exposed to xenon under certain pressure and it was supported by the fact that germination of conidia of the barley powdery mildew fungus was suppressed. Suppression of respiratory metabolism was also observed for broccoli and eggplant when they were preserved under certain pressure of xenon.

MEASUREMENT OF MEMBRANE HYDRAULIC CONDUCTIVITY BY A NEWLY DEVELOPED METHOD

Reducing water loss from vegetables is important to maintain freshness. The hydraulic conductivity coefficient (Lp) of cell membranes is indispensable to analyze the movement of water from cells, which leads to wilting and low metabolic activity. To measure Lp, extracellular solution must be replaced quickly to apply osmotic stress to the cells; however, conventional methods take a relatively long time, which leads to noticeable errors. We therefore developed a new method to measure Lp based on the principle that two liquids exhibit laminar flow through a relatively narrow space, for example, a tube having a small inner diameter. A microchannel having a diameter of 1.4 mm was designed. The microchannel has two inlets, and the flow rate of solution at each inlet can be used to determine the volume of each solution occupying the microchannel. Hence, an extracellular solution of protoplast fixed in a microchannel can be changed instantaneously by changing the flow rate of the solution. The Lp values of barley cotyledon and spinach leaf protoplasts were measured by both the developed method and a conventional method. Lp values measured by the conventional method were lower than those measured by the newly developed method. The developed method also showed less scattering in the measured Lp values because the errors caused by the experimental operation were reduced. In addition, the difference in values measured by both methods was examined by error estimation, and the values obtained by the new method were determined to be valid. With this method, the time delay to replace the extracellular solution was negligible and Lp was obtained without any error being caused by the time required for replacement.

Control of the state of water in persimmon for the extension of post-harvest life

Abstract Metabolism is based on intracellular chemical reactions which are enzyme mediated. The rate of enzyme reaction is regulated by the diffusion of substrate that is governed by the viscosity of water. As the formation of structured water by dissolution of xenon gas could make the viscosity of water larger, suppression of metabolism is expected because of resultant low rate of enzyme reaction. On this basis, structured water created by dissolution of xenon was confirmed by the change in spin-lattice relaxation time observed by proton NMR measurement. Then, xenon gas was applied to persimmon up to 0.25 MPa to make intracellular water structured and stored for 25 days at 278 K. The measurement of CO2 evolved from persimmon showed the suppression of respiratory metabolism and preservation of cellular structure was observed through a scanning electron microscope.

Development of the measurement method of membrane hydraulic conductivity by the use of microchannel

We have developed a new method to measure the hydraulic conductivity of cell membrane (L/sub p/), based on the principle that two liquids flow in laminar flow though relatively narrow space. The developed method has advantages that the number of the required cell sample is only one, and accurate measurement can be made as compare with the conventional method.

Measurement of membrane hydraulic conductivity by a newly developed method

Reduction of water loss from leafy vegetables is important to keep freshness. The hydraulic conductivity coefficient of cell membrane (Lp) is indispensable to analyze the movement of water from cells which leads to wilting and low metabolic activity. To measure Lp, extra-cellular solution must be replaced quickly to apply osmotic stress to cells, however, the conventional methods take a relatively long times which leads to noticeable errors. We therefore developed a new method to measure Lp, based on the principle that two liquids flow in laminar flow though relatively narrow space, for example, a tube having a small inner diameter. A micro-channel having a diameter of 1.4 mm was designed. The micro-channel has two inlets and the flow rate of solution at each inlet can be used to determine the volume of each solution occupying the micro-channel. Hence, the extra-cellular solution of protoplast fixed in a micro-channel can be changed instantaneously by the changing the flow rate of solution. The Lp of spinach leaf protoplasts was measured by both the developed method and a conventional method. Lp measured by the conventional method was 0.03 to 0.07x10-12[m/s/Pa] and that measured by the newly developed method was 0.076x10-12[m/s/Pa]. The difference in values measured by both methods was examined by error estimation and the value obtained by the new method was judged valid. With this method, the time delay for replacing of extra-cellular solution was negligible and Lp was obtained without the error caused by the time for replacement.