• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.7
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• pp.1055-1061
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• 2014

Innovative freezing technology is currently applied to preserve foodstuffs for long-term storage. Generally, the quality of frozen food is closely related to the types of freezing and thawing processes. In this study, we characterized the physicochemical properties of onions depending on freezing rate. When onions were frozen at $-40^{\circ}C$, freezing rates were 0.1, 0.5, and $0.7^{\circ}C/min$ depending on air-blast quick freezer mode. Onions were thawed by microwave irradiation at 400 W. Hardness of onion dramatically decreased after freezing and thawing compared with blanched onion. However, the fastest freezing rate did not affect hardness. Thawing loss of onion decreased with a faster freezing rate. For morphological observation, onion frozen at a faster rate showed a smaller ice-crystal size. Vitamin C content decreased upon blanching or freezing, but there was no significant difference according to freezing rate. Although free sugar content also decreased upon blanching and freezing, its highest content was at $0.7^{\circ}C/min$ freezing. Among organic acids, malic acid content was highest at $0.7^{\circ}C/min$ freezing. Based on this study, it could be suggested that a faster freezing rate is effective to improve frozen food quality in accordance with preventing tissue damage or minimizing destruction of nutrients.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.5
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• pp.322-327
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• 2000

For the stable production of high quality tea, the freezing resistance is a very important character. Most of the farmers have planted out-pollinated seeds that are not genetically pure. So, with small sample, a quick and simple method is required to test freezing resistance of lots of germ-plasm and early generation of hybrids. The absorbances(A530 nm) of TTC reduction solution at -5$^{\circ}C$ were positively correlated with resistance to photoinhibition of PSII in 6 hour photoinhibitory treatments, being significantly fitted by simple linear regression ($R^2$=${0.64}^{**}$). Chlorophyll fluorescence measured by Fv/Fm was found to be very useful in evaluating the relative levels of freezing resistance in tea.

• Journal of Embryo Transfer
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• v.10 no.3
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• pp.193-202
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• 1995

In order to improve the cryopreservatory techniques of livestock embryos, the quick freezing method which is directly plunged in liquid nitrogen via prefreezing procedure without freezing machine was carried out for mouse embryos treated with permeable and nonpermeable cryoprotectants. The viability of frozen-thawed embryos were evaluated by FDA vital dye test. The results obtained was summaried as follows: 1. A total of 720 embryos were recovered from frozen embryos for viability test. Evalution of the fluorescein diacetate(FDA) vital dye test with mice embryos were resulted of 2.3 total mean score - evaluted in orderly higher mean grade of P3 453 (63%), P2 133(18%), P1 51(7%) and P0 83(12%). 2. An all-round evalution of these combination, the highest viability was showed in 3M ethylene glycol + 0. 25M trehalose treated with the copper prefreezing. 3. Effects of permeable and nonpermeable cryoprotectants combination were evaluated by means FDA score. 3M ethylene glycol + 0.25M trehalose showed the highest survival rates of 2.8 mean FDA score. 4. Effects of permeable cryoprotectants were evaluated by mean FDA score but the results were not significantly different each other. 5. In evalution of the nonpermeable cryoprotectants, 0. 25M trehalose obtalned higher mean FDA score than of 0.25M sucrose and it was significantly different(P<0.05). 6. There was no significantly difference between copper and stainless-steel in prefreezing procedures.

• Korean Journal of Food Science and Technology
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• v.43 no.4
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• pp.509-512
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• 2011

To study the effect of freezing rate on the quality of freeze-dried rice porridge, freeze-dried rice porridge products were prepared with rice porridge pre-frozen at three different temperatures of -20, -40, and -70$^{\circ}C$. The porridge properties such as microstructure, mechanical properties, textural properties, and rehydration rate were determined. Scanning electron microscopy images indicated that fewer air cells were obtained with a larger size of freeze-dried rice porridge frozen at -20$^{\circ}C$ compared with that frozen at -40 and -70$^{\circ}C$. In contrast, quick frozen products at -70$^{\circ}C$ had more dense texture with higher mechanical strength, whereas slow frozen products exhibited higher rehydration rates than those of quick frozen products. In conclusion, the proper choice of pre-freezing temperature plays a decisive role when preparing freeze-dried rice porridge with optimum quality and convenience.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.293-305
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• 2023

To ensure the safety of underground infrastructures, ground can sometimes be first treated by cement slurry and then stabilized using artificial ground freezing (AGF) technique before excavation. The hydration heat produced by cement slurry increases the soil temperature before freezing and results in an extension of the active freezing time (AFT), especially when the Metro Jet System (MJS) treatment is adopted due to a high cement-soil ratio. In this paper, by taking advantage of an on-going project, a case study was performed to evaluate the influence of MJS and AGF on the ground temperature variation through on-site measurement and numerical simulation. Both on-site measurement and simulation results reveal that MJS resulted in a significant increase in the soil temperature after treatment. The ground temperature gradually decreases and then stabilized after completion of MJS. The initiation of AGF resulted in a quick decrease in ground temperature. The ground temperature then slowly decreased and stabilized at later freezing. A slight difference in ground temperature exists between the on-site measurements and simulation results due to limitations of numerical simulation. For the AGF system, numerical simulation is still strongly recommended because it is proven to be cost-effective for predicting the ground temperature variation with reasonable accuracy.

• The Korean Journal of Food And Nutrition
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• v.4 no.1
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• pp.1-8
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• 1991

This study was attempted to establish the basic data for effective utilization of the dried radish and sweet potato. The rehydration characteristic was carried out from these dried root vegetables in various conditions. The following results were obtained. The rehydration value was increased in glycine solution, whereas It decreased in lactic acid solution. Also the vacuum freezing was higher than that in hot air drying, and it was higher the slow freezing than in the quick freezing. The rehydration rate and the rehydration surface area curve were composed of three stages, and these stages were corresponded to each other. At the range of initial immersion to 2min., the largest rehydration rate was showed. The activation energy obtained from the Arrhenius plot of the rehydration rate constant(K) were 3. Bx103ca11g mol and 3.7$\times$103cal/g mol for dried radish and sweet potato, respectively.

• Korean Journal of Food Science and Technology
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• v.47 no.3
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• pp.350-358
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• 2015

Freezing is one of the main processes to extend the shelf life of foods. Before freezing, a thermal treatment is normally required to control the food quality. In this study, shiitake mushrooms were heated with boiling water and with superheated steam. After the thermal treatments, the samples were continuously frozen by an individual quick freezing (IQF) process, and put them into air-containing or vacuum packaging. Samples were stored at -12, -18 and $-24^{\circ}C$ for 24 weeks, and their physicochemical properties were determined. The lightness of the samples treated with boiling water and superheated steam was decreased by 12 and 15%, respectively, than that of the control. The hardness of all the samples rapidly increased after heat treatment. The contents of organic acids in the superheated steam treated samples were higher than those in the boiling water treated samples. Therefore, superheated steam treatment of samples may be a candidate thermal treatment to preserve frozen shiitake mushrooms.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.555-564
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• 1990

The headspace gas chromatographic(analytical) technique was used to evaluate the retention of volatiles in fruit juices during freeze drying as a function of freezing rate, the content of initial solid and chamber pressure. The effects of freezing rate and drying time on the volatile retention under the experimental conditions were marked, particulary at long freezing time. The retention of volatiles in the freeze dried was largely affected by the freezing rate. The highest volatile loss under the freeze drying conditions was observed during the first stage of drying. The behavior during freeze drying of the volatile substances was affected by high content of initial solid. The volatile retention was higher in quick freeze drying than slow freeze drying and low pressure than high.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.682-687
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• 1999

The destruction of tissues by volume increase at food freezing is accepted as one of the factor responsible for quality damage. For this reason, the internal pressure developed in meats were investigated with a pressure transducer during freezing, frozen storage and thawing. Increasement of 6.33% for volume and $942.17\;kg/cm^2$ for density at $-20^{\circ}C$ for beef were shown. In quick and slow freezing of beef, internal pressure reached to highest point after reached to the lowest point at initial of the zone of ice crystal formation. The internal pressure was approximately $8{\sim}10\;psig$ and pressure difference was about 1 psig, which was bigger in immersion freezing than that of still-air freezing. During frozen storage of pork, internal pressure of $1.84{\sim}2.32\;psig$ occurred repeatedly as a function of sample weight at material temperature difference of ${\pm}1^{\circ}C$. The internal pressure during thawing of pork was decreased slowly after rapid increase to the maximum for less than 5min at the beginning of thawing. Internal pressure value at thawing was higher than that at freezing in most cases. Internal pressure of beef with thermal equalized freezing was about $1{\sim}4\;psig$, which was lower than that of non-thermal equalized freezing. Also, freezing time was shortened to $10{\sim}20%$.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.215-218
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• 2003

In order to study the frost heaving characteristics of soil stabilitized with a quick lime, a cement and a briquette ash, frost heaving tests were performed with 2 kinds of soil sampled at Chonbuk-Do area. Frost heaving of no-stabilizing soil compacted with water content greater than optimum water content was increased as the frost period was increased but in case of samples with water content smaller than optimum water content, the frost period gave no affect about increase and decrease of the frost heaving. Both frost heaving of stabilizing and no-stabilizing soil with water content greater than optimum water content was decreased with the increase of the repetition number of freezing and thawing. There was no increase or decrease of frost heaving in the frost heaving test after 5 times of freezing and thawing.