• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.40-44
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• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• 한국식생활문화학회지
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• 제28권6호
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• pp.664-673
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• 2013

This study was conducted to investigate the physicochemical properties of mung bean starch and the quality characteristics of mung bean starch gels supplemented with gelatin and isolated soy protein (0, 2, 5%) during storage at $5^{\circ}C$ for 0, 24, 48, and 72 hours. The swelling power of mung bean starch supplemented with gelatin did not significantly change, whereas those supplemented with isolated soy protein (ISP) significantly increased. The solubility of mung bean starch supplemented with gelatin and ISP, however, significantly increased with increasing concentration. In addition, the soluble amylose and soluble carbohydrate of mung bean starch supplemented with gelatin and ISP significantly decreased with increasing concentration. In terms of pasting properties measured by the Rapid Visco Analyzer (RVA), the pasting temperature of mung bean starch supplemented with gelatin and ISP was not significantly different, whereas peak viscosity, minimum viscosity, final viscosity, breakdown, and consistency decreased. DSC thermograms showed that the onset temperature of mung bean starch supplemented with gelatin and ISP did not significantly change, whereas the enthalpy increased with the addition of 5% ISP. The lightness (L) and redness (a) of mung bean starch gels supplemented with gelatin, ISP, and without additives increased during cold storage, whereas the yellowness (b) decreased. The addition of gelatin and ISP suppressed changes in L, a and b of mung bean starch gel during cold storage. Synereses of mung bean starch gel supplemented with gelatin and ISP was lower than that without additives, with the addition of gelatin suppressing synereses more than ISP. The addition of gelatin and ISP also suppressed increases in hardness, chewiness, and gumminess of mung bean starch gels during cold storage. In the sensory evaluation, the addition of gelatin and ISP suppressed increases in hardness and brittleness of mung bean starch gels during cold storage. The addition of 2%, 5% gelatin and 2% ISP also suppressed a decrease in the overall acceptability of mung bean starch gels during 24-48 hr cold storage. Thus, the addition of 2-5% gelatin and 2% ISP to mung bean starch is appropriate for suppressing the quality deterioration of 24-48 hr cold-stored mung bean starch gels.

• 원예과학기술지
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• 제34권6호
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• pp.898-911
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• 2016

Sugars play many important roles in plant metabolism and directly influence fruit quality. The effects of two edible coatings, 2% calcium chloride and 1% pullulan, on sugar metabolism in postharvest Huangguan pear fruit were investigated during cold storage. The respiration rate, sugar content and composition, sucrose metabolism enzyme activities [acid invertase (AIV), neutral invertase (NI), sucrose synthase (SS), and sucrose phosphate synthase (SPS)] and expression of the AIV gene were analyzed during storage at $0^{\circ}C$ for 210 days. Coating treatments slowed the decrease of sucrose and hexose, the respiration rate, and the activities of AIV, NI, SS and SPS, thus maintaining high total soluble solids (TSS) and titratable acid (TA) contents in the fruit. There were no significant differences in AIV expression or activity between the treated and control groups of fruits. Both of the coatings could inhibit the activities of sucrose-cleaving enzymes, thus slowing the decrease of sugar content and maintaining high fruit quality during cold storage.

• 한국동물위생학회지
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• 제25권1호
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• pp.15-22
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• 2002

This experiment was carried out to investigate the changes of egg qualify during storage in order to find out the proper storage condition. Fresh eggs were stored at cold condition ($5^{\circ}C$, relative humidity ; RH :$65\pm$3%) and room condition($25^{\circ}C$, RH :$40\pm$3%) during 10 weeks and examined microbiological quality, weight loss and interior quality periodically. Weight loss was indicated 17.93% at room condition and 2.56% at cold condition. The pH of egg white and yolk were increased from 7.94 to 9.03(average 13.72%) and from 6.16 to 6.57(average 6.65%) at cold condition and from 7.94 to 9.54(average 20.15%) and from 6.16 to 6.90(average 12.01%) at room condition respectively. But pH of egg white and yolk did not showed significant difference between before molting and after molting. Haugh unit was decreased from 82.0 to <30 at room condition after 3 weeks. The most frequent bacteria isolated were E coli, Staphylococcus leutus, S saprophyticus, Citrobacter freundii, Klebsiella oxytoca, Providencia rettgeri, and Pontoea spp. It was recommended that shelf life of unrefrigerated eggs would not be longer than 21 days at room temperature in summer.

• 설비공학논문집
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• 제26권2호
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• pp.72-78
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• 2014

In a cold chain, the refrigerator is also employed for defrosting, by using an electric heater, which consumes 15% of the power for the system operation. In this study, the condensation heat of the refrigerant was suggested as the heat source of defrosting heat, instead of that from an electric defrost heater. The heat for defrosting was stored to a phase change material (PCM, NMP : $52^{\circ}C$) in thermal storage, and was periodically supplied to the evaporator by a circulation loop of brine. As a result, a defrost time by the PCM was obtained that was less than or equal to that by the electric heater. Moreover, power consumption during defrosting was saved by up to 99% of that of the electric heater.

• Journal of Information Processing Systems
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• 제19권3호
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• pp.394-406
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• 2023

In this study, a real-time surveillance system using Internet of Things technology is proposed for vaccine cold chains. This system fully visualizes vaccine transport and storage. It comprises a 4G gateway module, lowpower and low-cost wireless temperature and humidity collection module (WTHCM), cloud service software platform, and phone app. The WTHCM is installed in freezers or truck-mounted cold chain cabinets to collect the temperature and humidity information of the vaccine storage environment. It then transmits the collected data to a gateway module in the radiofrequency_physical layer (RF_PHY). The RF_PHY is an interface for calling the bottom 2.4-GHz transceiver, which can realize a more flexible communication mode. The gateway module can simultaneously receive data from multiple acquisition terminals, process the received data depending on the protocol, and transmit the collated data to the cloud server platform via 4G or Wi-Fi. The cloud server platform primarily provides data storage, chart views, short-message warnings, and other functions. The phone app is designed to help users view and print temperature and humidity data concerning the transportation and storage of vaccines anytime and anywhere. Thus, this system provides a new vaccine management model for ensuring the safety and reliability of vaccines to a greater extent.

• 한국식품과학회지
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• 제11권2호
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• pp.131-137
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• 1979

수삼(水蔘)을 CA저장(貯藏)하여 그 저장효과(貯藏?果)를 검토하고 또 저장(貯藏)한 수삼(水蔘)으로 가공(加工)한 홍삼(紅蔘)의 품질(品質)을 평가(評價)한 결과(結果)는 다음과 같다. 1. 수삼(水蔘)을 보통 냉장(冷藏)하니 저장(貯藏) 100일(日) 부터 곰팡이가 발생하였으나 CA저장(貯藏)의 경우는 6개월(個月) 후(後)에 도 외관(外觀)에 이상(異狀)이 없었다. 2. 수삼(水蔘)의 중량감(重量減)은 저장(貯藏) 180일(日)에서 냉장구(冷藏區)가 9%, CA구(區)가 $4{\sim}5%$이었다. 또 경도(硬度)는 CA구(區)가 냉장구(冷藏區)보다 높았다. 3. 수삼(水蔘)은 저장(貯藏)에 따라 고미(苦味)가 감소(減少)하였고, 냉장구(冷藏區)는 CA구(區)보다 감소(減少)가 컸다. 4. 수삼(水蓼)의 호흡량(呼吸量)은 전(全) 저장기간(貯藏期間)을 통하여 CA구(區)는 냉장구(冷藏區)보다 낮았다. 5. 저장(貯藏) 180일(日)의 수삼(水蓼)으로 가공(加工)한 홍삼(紅蓼)은 gel화(化)가 불완전(不完全)하고, 껍질이 유리(遊離)되었을 뿐만 아니라 total saponin함량(含量)이 크게 감소(減少)하였다.

• 원예과학기술지
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• 제34권2호
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• pp.257-268
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• 2016

Physiological characteristics of five new apple cultivars from the Korean apple breeding program were evaluated as a function of harvest time and storage after harvest. Internal ethylene concentration (IEC), flesh firmness, soluble solids concentration (SSC), and titratable acidity (TA) were measured in 'Summer Dream', 'Summer King', 'Green Ball', 'Picnic', and 'Hwangok' apples at harvest, during shelf life at $20^{\circ}C$, and one day after cold storage at $0.5^{\circ}C$ in air. IEC increased during shelf life in 'Summer Dream', 'Summer King', and 'Green Ball' but not in 'Picnic' or 'Hwangok', regardless of harvest time. Flesh firmness decreased towards harvest time and decreased gradually with time in cold storage only in the former three cultivars. In turn, IEC increased during cold storage in the first three cultivars but not for the last two cultivars, irrespective of harvest time. Changes in SSC and TA did not consistently relate to harvest time or storage period but TA tended to decrease as IEC increased. Furthermore, IEC was negatively correlated with flesh firmness except in the 'Green Ball' cultivar but the significance level was much greater in 'Summer Dream' and 'Summer King' (p < 0.0001) than in 'Picnic' (p < 0.01) or 'Hwangok' (p < 0.05) cultivars. Flesh firmness was positively correlated with TA in the first three cultivars but not in the last two cultivars. Overall, the results indicate that cultivars for which IEC increased after harvest had reduced flesh firmness and TA after storage.

• 원예과학기술지
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• 제28권6호
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• pp.990-995
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• 2010

본 시험은 이상저온($-3.5^{\circ}C$ 이하에서 7시간 지속)에 의해 수체 상에서 동결된 사과 '후지' 과실들의 수확시기에 따른 품질차이를 비교하고자 실시하였다. 수확 시기는 동결피해 1일 전, 동결피해 2일 후, 동결피해 6일 후였다. 시험에 조사된 과실들의 수확시 가용성 고형물 함량은 $14^{\circ}Bx$ 이상이었다. 동결피해 후 수확한 과실의 수확 시 경도 및 산 함량은 동결피해 전에 수확한 과실보다 낮았다. 저온저장 중의 에틸렌 발생량은 동결피해 후 수확한 과실이 동결피해 전에 수확한 과실보다 높았다. 동결피해 후 수확한 과실의 저온 저장 동안의 품질저하는 동결피해 전에 수확한 과실보다 심하였다. 동결피해 후에 수확한 과실의 저온저장 출고 후 실온 1주일째의 품질 저하는 동결피해 전에 수확한 과실보다 더 심하였다. 동결피해 후에 수확한 시험구들간의 비교에서는 저온저장 8주까지 동결피해 6일 후에 수확한 시험구의 에틸렌 발생량 및 과실품질 저하가 동결피해 2일 후에 수확한 시험구보다 낮았으나, 이러한 차이는 저온저장 8주 이후로는 없었다. 과육 갈변증상 발생률은 $-3.5^{\circ}C$ 이하에서 7시간 동결될 경우 영향을 받지 않은 것으로 나타났다.

• 한국식품영양학회지
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• 제10권4호
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• pp.553-558
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• 1997

냉동상태로 포장하여 판매되고 있는 생선(대구살)을 대구지역 수퍼마켓에서 구입하여 냉장(R:refrigerating), 냉동(F:freezing), 냉장과 동결을 반복(RFR:repeated freezing and refrigerating)하는 3군으로 나누어 저온저장하면서 저장중의 중온균과 저온세균의 수, free drip량과 pH의 변화를 측정하여 이들의 상관관계를 비교하였다. 저장직전의 해동어육의 생균수는 중온균이 6.5$\times$104, 저온세균이 7.4$\times$103cells/g이었으며 냉장한 시료에서는 저장 8일, 냉장과 동결을 반복한 시료에서는 저장 16일 후에 107cells/g을 초과하여 초기 부패에 도달하였다. 동결시료의 경우에는 46일간의 전 저장기간 동안 저장 28일째에 약 106cells/g으로 생균수가 가장 많았으며 신선한 상태가 유지되었다. 저온저장 중 저장초기에는 중온균의 수가 약간 많았으나 저장기간이 경과하면서 저온세균의 수가 빠르게 증가하여 저장밀기에는 저온세균의 수가 중온균의 수보다 증가하였다. 저장 중 pH의 변화는 생균수의 변화에 비례하여 증가하였으며 r=0.73-0.96의 높은 상관관계를 나타내었다. 저온저장 중의 drip량은 냉장시료에서 27.06$\pm$9.75, 냉동시료에서 27.56$\pm$8.02%로서 전 저장기간 동안 drip량은 큰 변화가 업이 두 시료간에는 유의적인 차이를 나타내지 않았다. 냉장과 동결을 반복한 시료는 저장기간이 길어질수록 drip량이 증가하는 경향으로서(r=0.84) 전 저장기간 동안의 평균치는 33.97$\pm$10.70%로서 냉장과 냉동시료에 비하여 20%정도 높은 값을 나타내었고 냉장 및 냉동시료와 유의적인 차이를 나타내었다.