• Korean Journal of Food Science and Technology
• /
• v.27 no.4
• /
• pp.537-545
• /
• 1995

Quality changes of lettuce were studied during storage to investigate the efficiency, cooling properties and the washing and storage effects of immersion-type hydrocooling. As a result of plotting the nondimensionalized lettuce temperature versus cooling time, its cooling rate coefficient was shown to be $-0.365\;min^{-1}{\sim}-0.255\;min^{-1}\;(R^2=0.99{\sim}0.88)$. Rate of weight loss was not significantly (p>0.05) different between lettuces with various treatment conditions during storage at $5^{\circ}C$. However, during storage at $15^{\circ}C$, weight loss of hydrocooled lettuce was lower than that of non-treated lettuce after from 10 to 15 days. Especially, The lettuce packed with PE was more effective than that packed with try in terms of packing condition after hydrocooling. Lettuce pretreated with sterilizing agent, packed with PE vinyl film, removed residual water after hydrocooling had lower decaying rate than any other lettuces. Changes of L and b values in hydrocooled lettuce were slower than those of non-treated one. During changes of chlorophyll content, the initial value, $115.7{\sim}147.3\;mg%$ was decreased to $50{\sim}60%$ after 25 days of storage at $5^{\circ}C$ and within 15 days of storage at $15^{\circ}C$. It could be presumed that the addition of sterilizing agent reduced the initial level of overall total and coliform count and its growth rate during storage. The respiration rate of hydrocooled lettuce at $5^{\circ}C$ was $23.95\;mg{\cdot}CO_2/kg\;hr$, which is 10% of those of non-treated lettuce.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.167.1-167
• /
• 2003

To maintain high quality and to extend the shelf life of intact and minimally processed apple cubes, the effect of heat shock on the texture and color of apple cubes (Fuji) was evaluated in this study. After peeled and cored, the apples were cut into cubes of 1.5 cm. The heat shock was immersion in heated water from 25$^{\circ}C$ to 95$^{\circ}C$ in 10$^{\circ}C$ increments for 2 min and cooling to storage temperature as soon as possible after heat treatment. The effect of heat treatment in terms of color and texture measurements with respect to time was investigated, respectively during 7 days storage at in LDPE film bags without sealing at 4$^{\circ}C$, and 95% relative humidity air. Results suggest that heat shock (55$^{\circ}C$, 2 min) may have effectively delayed browning, and there were significant changes in color of apple cube when the temperature of heat shock is above 75$^{\circ}C$. And hardness, stiffness and firmness, which were used to describe texture, behaved similarly in the textural qualities. It was shown that the texture of the apple cubes was decreased with temperature increase. The value of them were most decreased to 70% of the initial ones after treated with 85$^{\circ}C$ and 95$^{\circ}C$ on the lust day.

• Corrosion Science and Technology
• /
• v.14 no.2
• /
• pp.47-53
• /
• 2015

Recently, the bending process is greatly applied to fabricate the pipe line. Bending process can reduce welding joints and then decrease the number of inspection. Thus, the maintenance cost will be reduced. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. By this thermal process, corrosion properties and microstructure can be affected. This work focused on the effect of induction heating bending process on the properties of ASME SA106 Gr. C low carbon steel pipes. Microstructure analysis, hardness measurements, and immersion corrosion test were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. Hardness was measured using a Rockwell B scale. Induction heat bending process has influenced upon the size and distribution of ferrite and pearlite phases which were transformed into finer structure than those of base metal. Even though the fine microstructure, every bent area showed a little lower hardness than that of base metal. It is considered that softening by the bending process may be arisen. Except of I2, intrados area, the others showed a similar corrosion rate to that of base metal. But even relatively high rate of intrados area was very low and acceptable. Therefore, it is judged that induction heat bending process didn't affect boric acid corrosion behaviour of carbon steel.

• Korean Journal of Rural Living Science
• /
• v.5 no.1
• /
• pp.1-8
• /
• 1994

This study was conducted to examine whether there is any effect of the local body exposure to hot and cold alternate stress on the blood flow and heart rate. Environmental condition was $20^{\circ}C$ air temperature, 65% relative humidity and 0.2m/s air movement. 22~32 years old four healthy female subjects wore clothes which they felt comfort sitting on a chair. And then their left hand was immersed twice in ($42^{\circ}C$\;and\;15^{\circ}C$ water alternately. Two of the subjects (E-group) were continually exposed to above condition 12 times. While, the other two (C-group) were exposed twice only at the 1st and 12th time of E-group's exposure. The results obtained from this experiment were as follows. \circled1 The initial response of the finger blood flow in I-group to the thermal stress showed more sensitively at the post-training than pre-training. \circled2 Heart .ate was higher in hand immersion at hot water ($42^{\circ}C$) than at cold water ($15^{\circ}C$) \circled3 The pattern of the blood flow of the finger and heart rate was different between E-group and C-group.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.3
• /
• pp.136-142
• /
• 2019

Nuclear power plant concrete structures are in contact with the coast, and durability due to chloride attack is very important because it is used as cooling water by taking seawater. For this purpose, a 3-year long-term saltwater immersion test was carried out to evaluate chloride ion diffusion coefficient and age apponent (m) The m values of the foundation with 4,000 class was 0.35 ~ 0.39, similar to KCI or ACI suggested values. essential service water constructions and tunnels of 5,000 class were 0.44 ~ 0.53 and 6,000 class, and 0.62 of reactor containment buildings were similar to the proposed values of FIB. As a result of the prediction of the service life with the measured age coefficient, all the safety related concrete structures of the nuclear power plants satisfied the service life of more than 60 years.

• Korean Journal of Food Science and Technology
• /
• v.30 no.2
• /
• pp.341-347
• /
• 1998

To develop simple and accurate analytical method for freezing time prediction of beef and tylose under various freezing conditions, freezing time (Y) was regressed against the reciprocal $(X_3)$ of difference of initial freezing point and freezing medium temperature, reciprocal $(X_4)$ of surface heat transfer coefficient, the initial temperature $(X_1)$ and thickness $(X_2)$ of samples which should cover most situations arising in frozen food industry. As results of the multiple regression analysis, equations were obtained as follows. $Y_{tylose}=3.45X_1+7642.84X_2+4642.67X_3+2946.89X_4-431.33\;(R^2=0.9568)$ and $Y_{beef}=0.68X_1+7568.98X_2+2430.78X_3+3293.26X_4-299.00\;(R^2=0.9897)$. These equations offered better results than Plank, Nagaoka and Pham's models, shown in satisfactory agreement with models of Cleland & Earle and Hung & Thompson when were compared to previous models, and the accuracy of its was very high as average absolute difference of about 10% in the difference between the fitted and experimental results. Also, thermal diffusivities of beef and tylose were measured as $4.43{\times}10^{-4}m^2/hr$ and $4.39{\times}10^{-4}m^2/hr$ at $6{\sim}7^{\circ}C$, $2.42{\times}10^{-3}m^2/hr$ and $3.32{\times}10^{-3}m^2/hr$ at $-10{\sim}-12^{\circ}C$. Initial freezing points of beef and tylose were $-1.2^{\circ}C\;and\;-0.6^{\circ}C$, respectively. Surface heat transfer coefficients were estimated $20.57\;W/m^2^{\circ}C$ with no-packing, $16.11\;W/m^2^{\circ}C$ with wrap packing and $13.07\;W/m^2^{\circ}C$ with Al-foil packing, and the cooling rate of immersion freezing method was about 10 times faster than that of air blast freezing method.