Erythritol slurry is promising as heat medium because of its advantages in heat capacity and heat transfer characteristics. In this study, the crystal growth in erythritol solution is investigated to clarify the fundamental characteristic of erythritol slurry. First, the erythritol crystals in the erythritol slurry having various initial concentration and solid fraction were observed. As the result, it was found that the crystal diameter increases with the initial concentration and crystal agglomeration is facilitated when the initial concentration is higher than 80wt%. Although the crystal diameter slightly increases with the solid fraction, the crystal agglomeration is not facilitated by the increase in solid fraction. Second, the crystals were classified into three groups by size, and the mass fraction of each crystal group was measured. As the result, it was found that crystal size increases with the initial concentration, and the mass fraction of the large crystal markedly increases with solid fraction of the slurry. Moreover, it was found that the crystal size can be decreased as the stirring speed of the slurry increases, and it can be also decreased by adding small amount of mannitol to the erythritol solution.

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We proposed erythritol slurry as a heat transfer medium for medium/low temperature thermal utilization. We investigated the blockage condition of erythritol slurry flowing in cooled pipe, to avoid the blockage in the pipe transportation of erythritol slurry. As the results of the experiment, we clarified the following tendencies. When Reynolds number is less than 1100, erythritol crystals sinks the bottom of the pipe, and it causes blockage because of accumulation of sinking crystals. When Reynolds number is over 1100 and it forms heterogeneous flow, erythritol crystals adheres on the top of the pipe. The adhering crystals cause accumulation of the other crystals, and eventually it results in the blockage. When Reynolds number is larger and it forms homogeneous flow, the accumulation of the crystals does not occur even after crystal adhesion, and the erythritol slurry can flow continuously. The transition Reynolds number from heterogeneous flow to homogeneous flow is strongly affected by the solid fraction of erythritol slurry. As a result, it can be said that the blockage condition depends on not only flow velocity and cooling temperature but also flow pattern.

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World countries are planning to prohibit the use of current refrigerants and replace them with lower-global-warming potential (lower-GWP) refrigerants to reduce the emission of greenhouse gases from heat pumps. However, most of these refrigerants are relatively unstable and have weak flammability. Existing research does not conclusively prove their oxidative decomposition in the event of leakages, although it is suggested that humidity has an effect on their flammability limits. In this study, the lower limit temperature of oxidative decomposition was measured to assess the risk of using lower-GWP refrigerants that may possess weak flammability. The onset of decomposition and the generation of hydrogen fluoride of lower-GWP and conventional refrigerants were measured using a heating tube as a hot surface. Furthermore, the results verified the effects of temperature, humidity, refrigerant type, and hot wall materials.

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In recent years, greenhouse gas control and energy saving have been required to prevent global warming. In residential air conditioners, switching to R 32, for which the GWP is as low as 1/3 of R 410A and superior in terms of safety and economy, is being pursued. Several new HFO-based mixed refrigerants have also been proposed which is excellent in terms of low GWP. Therefore, we have compared the performance among R 32 and newly proposed HFO-based mixed refrigerants by drop-in test and system simulation for VRF systems in commercial buildings since swiching to low GWP will be required in the future.

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The objective of this study is to clarify the temperature and humidity distribution in the desiccant rotor. Thus we focused on the small sensors for “Internet of Things”. By installing the small sensor in the desiccant rotor, continuous measurement inside the rotating material become possible. First part of this report, correcting method for sensor response delay when temperature and humidity input were changed was examined. We conducted an evaluation test to obtain the delay characteristics of the small sensors. The results of the test, the response delay showed the same characteristics regardless of the differences in air temperature and humidity. The correction equations for the temperature and humidity were obtained. Second part of this report, adsorption/desorption measuring test was conducted. To clarify the humidity distribution, a desiccant rotor with small sensors was created. Two sensors were buried at 5mm points from each surfaces of rotor. As shown in Fig.A-1, the amount of dehumidification increased by increasing the rotational speed. Fig.A-2 shows temperature and humidity distribution in the circumferential direction of desiccant rotor. In this case, it can be seen the temperature distributions were agreed with values measured with fixed thermocouples. In addition, the distributions of absolute humidity due to the change in rotational speed was clarified. The peaks of absorption/desorption are shifted backward by increasing of the rotational speed. Also, breakthrough was confirmed in the regeneration zone under the condition of 7 rph.

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We investigated the effects of storage conditions on the quality parameters (texture, softness and juiciness) of fried chicken products. Texture profile analyses showed the storage condition (25℃ 40%RH) to maintain the quality of fried chicken products comparing with immediately after frying. On the other hand, samples stored at higher temperature or higher humidity resulted in acceleration of deliquoring and hardening. Fried chicken products stored at 40 ℃ and 40%RH could maintain the weight, texture and juiciness during storage.

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“Ikura,” a seasoned salmon roe product in Japan, is produced mainly from eggs of the chum salmon caught during spawning migration. Owing to the high volumes of salmon caught during peak season, appropriate storage and processing methods are essential to maintaining egg quality. We investigated the processing properties of fresh or frozen-thawed salmon eggs at different maturity levels, focusing on hardening during storage. Our results confirmed that little hardening during storage occurred in eggs in the skein state in the abdominal cavity with a low maturity level, whereas substantial hardening occurred in the individual egg grains in the peritoneal cavity. Similar results were obtained using fresh and frozen salmon eggs, and the hardening of matured salmon eggs depended on the storage time and temperature. Based on SDS-solubility and SDS-PAGE analyses, the macromolecularization of egg membrane proteins occurred during egg hardening. The frozen eggs tended to harden faster than fresh eggs, and the hardening pattern was slightly different between these eggs; these differences may be explained by various factors, such as protein polymerization and degradation. The hardening of the egg membrane progressed after salting, and this phenomenon is likely to occur during salting and aging in industrial manufacturing.

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In a preliminary study to clarify the factors affecting the quality deterioration of surimi-based products, the physical properties and drip loss of five different types of commercial surimi-based products (Itatsuki-kamaboko, Chikuwa, Satsuma-age, Datemaki, and Hanpen) at different freezing conditions were evaluated. After frozen storage, the breaking strength and breaking strain of Itatsuki-kamaboko, which is a two-step-heated surimi gel without starch, decreased with frozen storage, while for the other products, which are direct-heated gels containing starch, the breaking strength and breaking strain increased. Drip loss increased after frozen storage, and the thawing drip was higher with Itatsuki-kamaboko than with other products. These changes were notable in samples subjected to slow freezing than subjected to quick freezing. Moreover, the results of physical properties and drip loss corresponded to the change in sensory characteristics. Thus, the quality change in frozen surimi-based products might be correlated to not only the freezing conditions but also the heating methods and ingredients used.

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As a means of exporting agricultural produces, air transport is mainly adopted to keep them fresh in Japan. On the other hand, marine transportation has been focused to reduce freight costs recently. Although it is necessary to consolidate various kinds of fresh produces to fill a container, fruit and vegetables have each suitable storage temperature. Here, we attempted to develop the dual temperature reefer container, which includes two rooms set at 0℃and 10℃ individually, and considered the design guideline by using CFD (Computational Fluid Dynamics). The validity of the prediction model was verified by comparing the measured temperature and predicted temperature and then temperature distribution and velocity distribution of the air in the container was visualized under the outside air temperature of 38℃ and 0℃ and various conditions. As a result, we could obtain basic guidelines to design the dual temperature storage container.

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The process of freezing and thawing causes the discoloration in the body surface of red-colored marine fishes such as alfonsino; which lowers their commercial values. The astaxanthin content and dispersion of erythrophore in the scale of alfonsino were measured to investigate the causes of the discoloration during freezing and thawing. Color measurement of the surface of alfonsino using the computer vision system showed that the discoloration during freezing and thawing was not affected by the storage period at –30 °C. In addition, there was little change in the astaxanthin content in the scale of alfonsino before and after freezing and thawing. The aggregation of erythrophores and damages to iridophores by freezing and thawing were confirimed by microscopic observations. These results demonstrated that the discoloration in alfonsino during freezing and thawing was caused not only by the oxidization and degradation of astaxantin, but also by the structural changes of the chromatophore in the scale.

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Mackerel is weak against freezing, therefore a high quality freezing method that prevents deterioration is essential. We investigated the effects of freezing condition (freezing atmospheric temperatures at －20, －40, － 80^oC and －196 ^oC) and lipid content on ice crystal size, K value, drip loss and pH in frozen mackerel. Lipid contents of mackerel effected on the K values, drip loss, and ice crystal sizes in frozen mackerel. Therefore, selected freezing conditions for different lipid content in mackerel would lead to regulate quality parameters such as K value, drip loss and ice crystal size.

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The effect of the freezing process and frozen storage periods on the microstructure of cooked glutinous rice has been investigated. Cooked glutinous rice (cv. Koganemochi) was frozen and stored in a household freezer (about -22 °C) during 1, 5, 10, 30 and 60-day storage periods. Its microstructure was observed by using fluorescence staining method and the morphology of ice crystals including equivalent diameter and number was analyzed. Colorimetric measurements were conducted after natural and steaming thawing on samples of each storage period. It was found that average equivalent diameter and number of ice crystals increased with storage period from 5 days, and recrystallization occurred in temperature fluctuation during freezing process and storage affected microstructure of glutinous rice. Moreover, by analyzing the distribution of ice crystals, it was found that most of them are under 10µm in each storage period. Frozen stored glutinous rice after 60 days showed darker and more unpleasant color than freshly cooked one by both thawing methods. Since the tendency of color change during the whole frozen storage was unstable, it could be assumed that the control of thawing process should not be neglected.

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The effects of the freezing process and frozen storage periods on rheological parameters of freshly cooked and freeze-thawed glutinous rice have been investigated. Cooked glutinous rice (cv. Koganemochi) was frozen and stored in a household freezer at -20°C for 1, 5, 10, 30 and 60 days. After steaming and natural thawing processes, creep-recovery test (0.1N, small deformation), texture profile analysis (TPA) test (50% deformation) and the tensile testing (20N, 100% deformation) were performed on one-grain and block-shaped glutinous rice respectively by a rheometer, to measure the rheological parameters of the samples. One-grain samples showed more significant differences with freshly cooked rice in tensile testing, while block-shaped ones showed more in creep recovery tests. There were few significant differences in any fracture characteristics and viscoelastic properties between steaming and natural thawing methods for both block-shaped and one-grain samples in each storage period. The TPA results demonstrated that natural thawing method would produce softer as well as less sticky glutinous rice products during 60-day frozen storage.

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Pizza dough samples were frozen and stored at different temperature (-5̊C, -15̊C, -25̊C, -35̊C and -45̊C) and for different storage periods (1 day, 15 days, 25 days and 35 days) to measure the baking characteristics of the samples in a hot air (HA) and superheated steam (SHS) oven. Baked samples were employed for the measurement of surface color and moisture content. The moisture content of the samples frozen at -5̊C significantly decreased after 15 days of frozen storage. The surface color of the SHS-dried samples changed more drastically than that of HA-dried samples. Compared with HA, the SHS baking showed the potential to give the frozen pizza dough higher thawing rate, less baking time, and faster browning ability. The combined effect of initial condensation, crust thickness and water redistribution from crumbs to crusts might have played important roles in differentiating the HA- and SHS-baked samples. Different freezing temperatures from -5 ℃ to -45 ℃ did not cause any significant difference in color.

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[in Japanese]

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Five Philippine durian cultivars - Puyat, Duyaya, GD69, Native, Arancillo, were subjected to consumer intensity-ranking test with 50 durian consumers as panelists to determine the correlation between the experimental measured values and the consumers' perceived intensity of the different durian quality attributes: color, texture, physicochemical properties, sugars, and organic acids content. Preference ranking test was also performed to identify the most preferred cultivar based on the five quality attributes evaluated. Results of the intensity ranking showed a good correlation between the experimental values and sensory perception on the color, texture, sweetness and overall flavor. Same trends in the degree of intensity were observed in the measurements, objective and sensory analysis. In the preference-ranking test, results revealed that Duyaya was the most preferred cultivars in terms of the color, while Arancillo was rated most preferred for the texture. In reference to the taste/flavor, the top choices were Arancillo, Duyaya, and Native. On the other hand, Puyat, GD69, and Arancillo registered the highest consumer preference in regard to aroma, although the mean rank of the former did not seem to differ with the two former cultivars. Finally, upon consideration of the overall preference, our findings suggested that Duyaya, Arancillo, and Native were more favored cultivars over Puyat and GD69.

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Ice crystals play an important role in the degradation of frozen food quality. Quality degradation occurs even in the frozen storage process owing to recrystallization. On the other hand, it is assumed that ice crystals formed with higher nucleation have the potential to be resistant to ice recrystallization since they have homogeneous size distribution of ice crystals when considering the mechanism of ice recrystallization. In this study, recrystallization behavior and quality degradation in oy bean curds prepared by freezing accompanied with supercooling (SCF) were investigated. As a result, ice crystal in SCF maintained the initial character of small particle size and homogenous ice structure after 28 day storage at -5°C, even though the characteristics of ice crystals in Conventional rapid freezing(CRF) and Conventional slow freezing (CSF) were changed dramatically during storage. Additionally it was observed soy bean curds prepared by SCF maintained their softness rather than those prepared by CRF and CSF; furthermore, SCF samples prepared with relative lower resolving temperatures of supercooling maintained the softness rather than the SCF samples prepared with relatively higher resolving temperature of supercooling maintained the softness rather than the SCF samples prepared with relatively higher resolving temperature of supercooling. The results indicated that the homogenous ice structure determined by SCF is an effective factor in preventing quality degradation as well as recrystallization, even though the storage temperature is higher.

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