When kimchi is frozen and thawed, the amount of lactic acid bacteria (LAB) and yeast is usually reduced by more than 2 logs, and its texture including its crispness and hardness are changed significantly. As a possible means to minimize these problems, various freezing (direct freezer with -25, -40, and -60oC and plate freezer with -40oC) and thawing methods (radio frequency (RF) thawing, plate thawing, and room temperature thawing) were investigated in terms of the amount of LAB and texture of kimchi. From the use of plate freezing and plate thawing, the amount of LAB of white cabbage kimchi could be maintained by more than 10% of its initial amount while that for red cabbage kimchi could be maintained by more than the initial amount. Pretreatment with trehalose (19 oBrix soluble solid content) to salted Chinese cabbage could maintain kimchi’s hardness and crispness. In order to maintain the texture and the amount of LAB in kimchi, the use of the plate freezer (-40oC) and the plate thawing (20oC) seemed to be effective with the assistance of trehalose.

In this study, a controlled atmosphere (CA) storage system is proposed as a storage method for prolonging processing period. Persimmon was placed in CA storage at 0.5oC±0.5 for 92 d. The qualities of the stored persimmons were compared to determine the possibility of extending shelf life. ‘Sangjudungsi,’ which was harvested on October 26, 2017, was applied to the persimmons. In order to compare differences according to size, the persimmons were classified into Size No. 2 (170 g) and Size No. 3 (145 g). In the result, the yellowness of CA-stored persimmons was 26.3% lower than that of cold-stored ones, confirming that after-ripening was delayed. The firmness of CAstored and Size No. 3 persimmon was higher than that of cold-stored and Size No. 2 persimmon. Tannin decreased significantly in cold storage, but it tended to increase in CA storage. The sugar content of Size No. 3 was lower than that of Size No. 2, but there was no difference in tendencies according to the storage method. Weight loss in CA storage was lower than that in cold storage. A comparison of color difference, firmness, sugar content, tannin, and weight loss ratio showed that CA storage was more effective in improving shelf life than cold storage.

Commercial direct refrigerators have good energy efficiency, but are difficult to use for supercooled storage due to their large temperature deviation. Placing insulators and conductors inside the refrigerator could reduce these temperature deviations to within 0.3 degrees, allowing for the supercooled storage. The supercooled storage of salted Chinese cabbages during ten weeks was progressed to compare the other low temperature storages. The nucleation temperatures of salted Chinese cabbage were around -2.5oC and the freezing points were around -0.4oC, so -2oC was selected for the supercooled storage. The growth rate of lactic acid bacteria and yeast at -2oC storage was lower than that at 2oC storage. The reducing sugar was maintained higher due to the growth rate of lactic acid bacteria. The supercooled storage had an effect of delaying the fermentation of the salted Chinese cabbage, which may have the effect of delaying the fermentation of kimchi. This enhancement method of the direct refrigerator was effective for the supercooled storage and would be promising for commercial use.

For the vessel export of strawberries, modified atmosphere package (MAP) using polyamide (PA) film and linear low density polyethylene (LLDPE) film was investigated to extend the shelf life of strawberries. Because the temperature and relative humidity changes of the MAP were lower than the changes of the control, the weight loss of the MAP were lower than that of the control. The low oxygen level and high carbon dioxide level were effective to decrease the fungal decay rate and to increase the hardness of strawberries. The Hunter’s color differences before and after storage showed no distinct difference between the MAP and the control. The lightness had a tendency to decrease while the redness increased. There were no significant changes of the soluble solids during the storage. The shelf life of strawberries could be extended to 16 days using the MAP considering the weight loss and the fungal decay rate. Thus, this MAP method using PA film and LLDPE film was effective to extend the shelf life of strawberries.

The main purposes of this study were to identify the factors affecting the supercooling property and to improve the possibility of supercooling storage of fruits and vegetables. Freezing point and nucleation temperature, moisture content, hardness, sugar content, and pH of nineteen fruits and vegetables were measured and Pearson correlation analysis was performed. Freezing point showed a statistically significant correlation with moisture content and sugar content (p<0.01), while ice nucleation temperature showed a correlation (p<0.05) only for sugar content. In particular, the water content and sugar content did not show any correlation with the freezing supercooling difference (FSD). From the correlation analysis between FSD, aerobic bacteria, lactic acid bacteria, yeast, and mold, FSD showed a correlation (p<0.01) with aerobic bacteria. The experiments of the saline solutions inoculated with aerobic bacteria at different concentrations showed FSDs of about 2 for saline inoculated with 9.4 log CFU/mL and about 6 for saline inoculated lower than 5 log CFU/mL. Therefore, the aerobic bacteria concentration was determined to be a key factor affecting the supercooling storage of fruits and vegetables.

The O2 and CO2 concentrations in controlled atmosphere (CA) rooms are determined by the respiration of produce like apples and the airtightness of the CA room, with gas in the CA room controlled by O2 and CO2 removal as well as respiration (CO2 increase and O2 decrease). The purpose of this study was to evaluate the validity of the gas exchange model for O2 removal, CO2 removal, the rate of O2 decrease and CO2 increase by respiration of apples, and airtightness of the CA room. It took 17.5 hours to reduce O2 concentration from 20.9% to 2.0% after loading 4.3 tons of Fuji apples into the CA room, which was 4.2 hours longer than the 13.3 hours of the model formula. After the CO2 concentration rose to 0.5% due to respiration, it took 4.7 hours to lower the CO2 concentration to 0.2%, which was 0.6 hours longer than that of the model equation. The rate of CO2 increase by respiration was 0.021%/ h, which was similar to the model equation (0.017%/h). Also after 4.7 hours, the O2 concentration decreased by 0.1% which was also in line with the model equation (0.13%/h).

The variations of internal temperature, relative humidity (RH) and gas concentration in the pallet modified atmosphere package (MAP), using polyamide (PA) film and linear low density polyethylene (LLDPE) film, were investigated to extend the shelf life of tomatoes and paprikas. The temperature and RH inside the MAP were higher than that in the cold room, but there was no water condensation inside the MA film. The ethylene concentration in the MAP was maintained below 10 ppm. Oxygen level was stabilized at 2 to 5% during the storage and carbon dioxide level was also stabilized at 15 to 20%. The weight loss of the MAP tomatoes and paprikas was lower than that of the control because the RH in the pallet MAP was higher than that of the cold room. The fungal decay rate in the pallet MAP was also lower than that in the control due to a low oxygen concentration rate. There were no significant differences in the soluble solids, titratable acidity and Hunter’s color, but differences did exist in the hardness between the MAP and the control. So, this pallet MAP method was effective at extending the shelf life of tomatoes and paprikas considering the weight loss, fungal decay and hardness.

소 도체의 등급 판정은 육량과 육질의 품질을 고려하여 숙련된 전문인력에 의해 수행되고 있다. 육질의 품질을 결정하는 중요한 인자로 근내지방도, 지방색, 육색 등이 이용되고 있다. 소도체의 품종, 성별, 연령에 따라 근섬유의 특성과 근내지방의 시각적 발현특성이 다르므로 측정자간 시각적 해석에 오차가 발생할 수 있다. 주요 판정인자들을 객관적으로 판정하기 위한 자동 측정기술의 개발이 필요하다. 본 연구는 근적외선 분광 영상을 이용하여 소 도체의 육질 판정 가능성을 조사하기 위하여 수행되었다. 다섯 등급(1++, 1+, 1, 2, 3)의 소 도체에 대하여 배최장근(등심부위)의 1,000-1,700 nm 영역의 분광 영상을 측정하였고, 육질부분과 지방부분의 분광 특성을 조사하였다. 그 결과 근적외선 분광 영상기술을 이용하여 육질부위와 지방부위의 구분이 가능하였으며, 근내지방도 예측도 가능하였다.

This study was conducted to propose the conditions of controlled atmosphere (CA) storage suitable for the storage of winter Chinese cabbage and to investigate the maximum storage period of Chinese cabbage based on the results of the quality analysis for CA storage. The weight loss rate of Chinese cabbage stored at 194 days in low temperature storage was about 2 times higher than that in CA storage. The trimming loss rate of Chinese cabbage stored at low temperature was 1.5 times higher than that of CA storage after 83 days of storage. Bolting of Chinese cabbage was observed in only low temperature storage. The Chinese cabbage firmness of CA storage was not different in the range of 5.7-6.2 N, while low temperature storage gradually increased after 83 days of storage and was 7.5 N at 194 days. The incidence of mold occurred after 83 days in low temperature storage, while in CA storage it occurred after 153 days. In the quality evaluation, CA storage for Chinese cabbage was rated 1.5-1.9 points higher than the low temperature storage. The maximum storage period of Chinese cabbage at low temperature storage was 83 days and that at CA storage 153 days.

Weight loss that influences quality and farmer incomes is affected by the storage environment of agricultural products. The interior of storage should be maintained at high humidity to prevent the weight loss of products which contain a lot of moisture. The research had constantly proceeded with change in the heat exchanger surface areas, humidity systems, and weight loss forecast to maintain high humidity within storage. Relative humidity that exerts an effect weight loss of crop is influenced by storage temperature, leak state, and volume of product. When weight loss is predicted, different conditions of these factors are derived. In case of CA storage, ways of forecasting the weight loss become easier compared to cold storage due to sealed storage with external environment during storage period. In this study, apples were stored in purge-type CA storage and weight loss has been predicted by using operating characteristics and environmental conditions. As a result, humidity variation in the storage fluctuates with the operation of the unit-cooler. Furthermore, unit-cooler operation factor is influenced by outside temperature and respiration heat. Prediction value of weight loss according to temperature and humidity has been most accurately predicted. Prediction value through defrosting water measured shows unit-cooler work quality. K-value needs verification to calculate the VPD method.

본 연구에서는 현장에서 필요한 겨울배추 CA저장에 적합한 조건을 제시하고, 저온 저장한 배추와의 품질 및 저장 기간을 비교 분석하여 겨울배추의 최대 저장 가능기간을 제시하고자 본 연구를 수행하였다. 겨울배추 CA저장의 저장 조건은 0°C, 90-95%, O2 1.0-3.0%, CO2 0.2-5.0%로 최종 설정하였으며, 저온저장고와 CA저장고에 예건한 겨울배추를 각각 1.8 ton, 1.0 ton 입고하였다. 품질조사 항목은 중량감모율, 정선손실율, 경도, 곰팡이 발생율, 관능검사이며, 품질조사는 입고 후 0일, 52일, 83일, 153일, 194일차에 진행하였다. 194일 저온 저장한 배추의 중량감모율은 CA저장한 배추보다 약 2배정도 높았으며, 정선손실율도 저온저장이 CA저장보다 1.5배 많았으며, 저장 83일 이후부터 배추 내부의 추대현상이 저온저장에서 많이 관찰되었다. 경도의 경우 CA저장 배추는 5.7 - 6.2 N범위에서 큰 변화를 보이지 않은 반면, 저온저장 배추는 83일 이후부터 점차 증가하는 모습을 보여 194일에 7.5 N을 가졌다. 곰팡이 발생율의 경우 저온저장 배추는 83일 이후 발생하기 시작하였으며, CA저장 배추는 153일 이후 발생하여 70일 정도 곰팡이 발생을 지연시켰다는 것을 알 수 있었다. 관능검사의 경우 CA저장이 전반적인 평가항목에서 저온저장보다 1.5 - 1.9점 높게 평가되었다. 겨울 배추의 최대 저장기간은 저온저장이 83일, CA저장이 153일로 CA저장이 저온저장보다 약 1.9배 더 장기간 저장이 가능한 것으로 나타났다.

This study investigated the effects of 27.12 MHz radio frequency (RF) heating on heat transfer phenomena during the thawing process of frozen food. To determine the velocity of the RF thawing machine, samples were frozen at -80oC and subjected to different power treatments. The phase change times (-5 to 0oC) of frozen radish were 30, 26, 13, and 8 min; those of pork sirloin were 38, 25, 11, and 5 min; those of rump were 23, 17, 11, and 6 min; those of chicken breast were 42, 29, 13, and 9 min; and those of tuna were 25, 23, 10, and 5 min at 50, 100, 200, and 400 W, respectively. The heating limit temperatures of the radish, pork sirloin, rump, chicken breast, and tuna samples were 19.5, 9.2, 21.8, 8.8, and 16.8oC at 50 W; 23.5, 15.5, 27.3, 12.3, and 19oC at 100 W; 42, 26.9, 45.7, 22.1, and 39.4oC at 200 W; and 48.5, 54.7, 63.6, 57.3, and 44.9oC at 400 W. These results suggest that high-power RF improves thawing velocity and heating limit temperatures, and that an improvement on the operation of the RF thawing machine, according to food temperatures, is needed.

This study was carried out to indirectly predict the storage time limit, hardness, and acidity of Fuji apples in controlled atmosphere (CA) storage. A sensor installed inside the CA storage measured temperature, relative humidity, and gas composition data in real time. The respiration rate from five tons of apples in CA storage was calculated to predict the weight loss rate. As a result, the predicted and actual weight loss rate induced a predictable residual storage time equation that showed a significantly high correlation. The apple storage period showed a high reliability (R2=0.9322) because the predicted equation using respiration rate and number of days stored was about nine months for five tons of apples. Furthermore, the hardness and acidity prediction equation were derived from the quality analysis. However, there was not enough analysis sample correlation (the coefficient was as low as 0.3506 and 0.3144, respectively), but the tendency could be confirmed by reduced hardness and acidity. As a result, these quality prediction equations could encourage CA container distribution, effective for agricultural shipment regulation and increasing the ease of operations.

본 연구는 떫은감의 저장기간을 연장시키기 위한 CA저장에서 저장고 내부의 적정 기체 조성비를 파악하기 위하여 CA챔버 내부의 기체 조성을 다르게 유지하고 그 기체 조성이 떫은감의 품질에 미치는 영향을 조사하였다. 떫은감의 품종은 상주둥시를 이용하였으며 저장 온도 조건은 0~1℃, 습도조건은 90~95%로 유지하였고 기체 조성(O2, CO2)은 CA저장 5처리구(CA 1: 2.0~4.0%, 2.5~3.0%; CA 2: 2.0~4.0%, 4.5~5.0%; CA 3: 4.0~6.0%, 0.5~1.0%; CA 4: 4.0~6.0%, 2.5~3.0%; CA 5: 4.0~6.0%, 4.5~5.0%) 및 저온저장구로 구분하여 120일간 저장하였다. 감모율은 CA저장에서 CA 5 처 리구가 3.22%로 가장 낮았고 CA 2 처리구가 5.25%로 가장 높았으며, 저온저장구는 11.58%로 CA 처리구에 비해 약 2배 이상 감모율이 높았다. 떫은감의 과육경도는 CA 2 처리구가 1.09N으로 가장 높았으며 저온저장구는 0.39N으로 가장 낮게 나타났다. 당도는 CA저장에서 CA 5 처리구가 18.80°Brix로 가장 높게 나타났고 CA 2 처리구가 16.71°Brix 로 가장 적게 나타났으며, 저온저장구가 20.42°Brix로 CA 처리구에 비해 높았다. 감의 최종 적정산도는 저온저장구에 서 0.28%로 CA저장에 비해 높게 나타났으며, CA저장에서 CA 5 처리구가 0.23%로 가장 높았다. 저장기간 동안 과피 흑변의 발생률은 저온저장구에서 72%로 CA 처리구보다 최대 48% 높게 나타났으며, CA 처리구에서 CO2에 의한 과육 갈변은 나타나지 않았으나 95일 이후 연화가 급속하게 진행되었다. 저장병은 저장 후 95일에 CA 처리구에서 평균적 으로 10%가 발생하였으나, 저온저장구에서는 50%가 발생하였다.