The objective of this study was to compare the feeding effects of imported timothy hay, domestic Italian ryegrass silage (IRGS) and IRG dried by hot-air dry system (IRGHDS) under basic total mixed ration (bTMR) on rumination activity, milk production, and milk composition in lactating dairy cows. Eighteen Holstein dairy cows were divided into three groups: control (bTMR + imported timothy hay), treatment 1 (bTMR + IRGS) and treatment 2 (TMR + IRGHDS) groups. The study was conducted over a total period of 24 days, including a 10 days adaptation period and a 14 days main experimental period. The results indicate body weight was not significantly different between the three groups (p>0.05), and rumination time was significantly higher in the treatment 1 group compared with the control group (p<0.001). Milk fat, protein, and lactose were not significantly different between the three groups (p>0.05), however, somatic cell counts were significantly lower in the treatment 1 group compared with the control group (p<0.001). As a result of the economic feasibility analysis, it is expected that feeding TMR using IRGS and IRGHDS will increase profit by 402.8 won/day and 331.4 won/day per cow compared to imported timothy hay. Therefore, IRGS and IRGHDS can be used as substitutes for imported timothy hay in feeding lactating dairy cows.

The objective of this study was to investigate the comparison of feeding a total mixed ration (TMR) containing imported alfalfa hay and TMR containing hot-air dried domestic alfalfa on rumination activity, milk production, and composition in lactating dairy cows. Ten Holstein dairy cows were divided into two groups: control (imported alfalfa hay + TMR) and treatment (hot-air dried domestic alfalfa + TMR) groups. The study was conducted over a total period of 18 days, including a 13-days adaptation period and a 5-days main experimental period. The results indicated no differences in total digestible nutrient and net energy intake between the imported and hot-air dried alfalfa. Body weight was not significantly different between the two groups (p>0.05), however, total feed intake and rumination time were significantly and tendentially higher in the treatment group compared with control group, respectively (p<0.001; p=0.075). Milk yield was not significantly different between the two groups (p>0.05), however, milk fat (kg) and lactose (%) concentration were significantly higher in the treatment group compared with control group (p=0.016; p=0.02). This study confirms that feeding TMR with hot-air dried domestic alfalfa results in no differences of feed intake, rumination activity, and milk productivity. Therefore, it is considered that hot-air dried domestic alfalfa can be used as a substitute for imported alfalfa on lactating dairy cows.

In this study, the effect of osmotic drying conditions of mangoes on hot air drying was investigated. Four different osmotic agents of 60 Brix, such as S60, SM10, HF80, and SG25, were prepared. Mango slabs were osmotically dried with the agents at a ratio of 1:4 (w/w) for up to 8 hours. SG25 showed the lowest weight reduction and moisture loss during the process. As a result of hot-air drying, all samples showed a high correlation with the Page model (0.9761~0.9997), and the required drying time of all samples that were osmotically dried was reduced compared to the non-osmotically dried group. After hot-air drying, the pH value increased according to the drying temperature. The L, a, and b values and the total polyphenol content also decreased. Through this study, the possibility of osmotic drying was confirmed to increase the efficiency of hot air drying of mangoes, which is expected to contribute to the industrial use of domestic mangoes.

This study aims to investigate the effect of drying temperatures on the quality characteristics and physicochemical properties of vegetables. Lettuce and napa cabbage were dried at 40, 50, and 60oC and analyzed for various quality indexes. Higher drying temperature induced the lower L* and higher a* and b* values of samples. Also, it resulted in lowering the rehydration ratio, pH, and total free amino acid content of dried vegetables. The outcome might be due to the damage to the internal structure of vegetables and the decomposition of free amino acids during thermal treatment. Higher drying temperatures led to higher soluble solid and total polyphenol contents due to the conversion of phenolic compounds from combined to free form during the drying process, which changed phenolic compounds from combined to free form. Consequently, samples dried at higher temperatures had higher DPPH radical scavenging ability. The final moisture content and drying time decreased as the drying temperature increased; moreover, the antioxidant activity increased. A lower drying temperature is beneficial to maintaining the chemical characteristics of crops.

This study evaluated the Protaetia brevitarsis larvae powder’s characteristic changes using hot air drying (60±2.5oC, 12 h) with different pre-treatment methods, including two sacrifice methods, two storage temperatures, and two defatting processes. Appearance, yield, moisture contents, pH, color, proximate analysis, volatile basic nitrogen level, DPPH radical scavenging activity, and total phenol content were assessed. Results revealed that a combination of blanching, defatting, and -20oC storage temperature resulted in higher total phenol contents, lower water contents, and lower volatile basic nitrogen levels than other methods. Defatted treatment resulted in a higher L-value than the non-defatted treatment. Taken together, these results indicate that a combination of -20oC storage, blanching, and defatting is the optimal pre-treatment method for obtaining P. brevitarsis larvae powder with high total phenol content, low water content, and low volatile basic nitrogen, taking into account cost efficiency considerations.

본 연구는 저장 온도를 달리하여 높은 상대습도의 환경에서 건조 감자를 저장하였을 때 발생하는 품질변화를 관찰하였다. 저장기간 및 건조온도가 증가함에 따라 L* value 는 감소하였고, a* 및 b* value는 증가하는 경향을 나타내었다. 수분활성도는 높은 습도 조건으로 인해 10일차부터 급격히 증가하였으며, 환원형 비타민 C 함량은 급격히 감소하는 경향을 나타내었다. pH 값은 저장기간 동안 완만하게 감소하였으며 40oC에서 저장했을 때 큰 폭으로 감소하였다. 저장기간 동안 대장균군은 검출되지 않았으며, 일반 세균 수는 저장 온도가 증가함에 따라 많이 검출되었다. 전체적으로 20oC와 30oC에서 저장한 시료 간의 차이는 크지 않았으나, 40oC에서 저장한 시료의 경우 큰 품질변화를 나타내었고, 밀봉된 상태로 저장한 대조구의 경우 품질변화가 적게 나타나는 것을 확인할 수 있었다. 따라서 본 연구결과를 종합해 볼 때, 밀봉하여 산소와 수분을 차단한 상태로 저장하는 것이 제품 고유의 특성을 유지하는데 가장 효과적이며, 높은 습도의 환경일 경우 낮은 온도로 저장하는 것이 품질 변화를 지연시키는데 도움이 될 것으로 판단된다.

In this study, the effects of heat-moisture treatment (boiling or steaming for 45 min) prior to hot air drying (70 o C for 8 h) on water activity (Aw), moisture (MC), Brix, color, and texture of dried sweet potato slices were investigated to identify the best pretreatment condition for producing dried sweet potato with the best eating quality. Dried sweet potato slices pretreated by boiling (BL) showed significantly lower Aw, MC, and hardness while Brix was significantly higher than with steaming (ST) treatment. There were no significant differences for the color, springiness, cohesiveness, gumminess, and brittleness indexes. At 8 h drying, the Aw, MC, Brix, and hardness of the BL and ST samples were 0.81 and 0.82, 19.71% and 25.53%, 53.80% and 49.40%, and 20.49 kg/cm 2 and 31.98 kg/ cm 2 , respectively. This information will be useful for manufacturers in the production of dried sweet potato slices. These findings provide evidence of the feasibility of heat-moisture treatments in the production of dried sweet potato.

In this study, the uniformity of the horizontal velocity and the temperature of each zone were investigated by computerized analysis method to divide the drying room into three multi - rooms to ensure the uniformity of flow inside the forced convection hot air dryer. The internal structure of the drying room of the dryer was modeled using Solidworks. In order to control the flow of hot air circulating in the drying chamber, the possibility of controlling the horizontal flow inside the drying room was verified by using a perforated plate, a guide vane, and a vertical plate. From the results of the flow visualization in the drying room, it was understood that the internal flows of the dryer models 1, 2 and 3 change from ununiform flow to uniform flow. From the analysis of velocity and temperature fluctuation, the results of the analysis of the dryer model 3 satisfied the design conditions.

본 연구는 금잔화를 꽃차로 이용하기 위해 열풍 건조 처리 시간에 따른 항산화 물질함량 및 항산화 활성을 분석하고, 최적 처리 시간을 구명하기 위해 수행하였다. 식용꽃 금잔화를 60℃에서 5시간, 10시간, 15시간 열풍건조 한 뒤 Hunter value를 측정하고 95% 에탄올을 용매로 하여 추출하였다. 항산화 물질인 총 폴리페놀, 총 플라보노이드, 총 카로티노이드 함량과 DPPH radical 소거 활성을 통한 항산화 활성, 이를 통한 항산화 물질 함량과 항산화 활성 간의 상관관계를 분석하였다. 처리시간이 증가함에 따라 Hunter value L 값과 +b값이 모두 감소하는 경향을 보였으며, 15시간 처리구에서 다소 많이 감소하였다. 또한, 항산화 물질 함량을 조사한 결과, 총 폴리페놀 함량은 처리 시간에 따른 차이는 없었으나 총 플라보노이드 함량과 총 카로티노이드 함량은 5시간과 10시간 처리시 함량이 다소 높았으며, 처리 시간이 증가함에 따라 감소하여 15시간 처리시 대조구와 차이가 없는 것으로 조사되었다. DPPH radical 소거 활성 분석 결과, 5시간과 10시간 처리시 대조구보다 활성이 높았으며, 총 카로티노이드가 DPPH radical 소거 활성 간의 상관관계가 높은 것으로 나타났다(p≤0.01, r=0.610). 따라서, 열풍건조한 금잔화는 총 카로티노이드가 항산화 활성에 기여하며, 5시간 및 10시간 열풍건조 처리가 금잔화의 항산화 물질 함량 및 활성 증가에 효과적인 것으로 판단되나 식물의 열처리 가공에 있어 오랜 시간은 내부 조직 및 항산화 물질 파괴에 영향을 미칠 수 있기 때문에 금잔화 열풍 건조 처리 시 5시간이 효과적일 것으로 판단된다.

This study examined the effects of drying methods of Aronia melanocarpa on contents of total polyphenols and flavonoids, antioxidant activity and anti-inflammatory activity. As a result, freeze-dried aronia extract (FDAE) significantly exhibited higher contents of total polyphenols and flavonoids (155.76 mg GAE/g and 105.70 mg QE/g) than hot-air dried aronia extract (HDAE) (134.93 mg GAE/g and 82.29 mg QE/g). Also, FDAE showed greater antioxidant activity than HDAE in both DPPH and ABTS. For anti-inflammatory activity, NO production from lipopolysaccharide activated RAW264.7 cell reduced at a dose-dependent manner in both FDAE and HDAE. However, reduction rate of NO production is higher in FDAE (62.7%) than in HDAE (33.5%). These results suggest that comparatively, freezedrying is a better method for preserving the antioxidant and anti-inflammatory activities and of aronia.

The aim of this research was to determine the effect of drying conditions (drying air temperature and drying time) on drying rate, effective diffusivity, and activation energy during hot-air drying of jujube slices. Jujube slices were dried in a laboratory scale convective hot-air dryer at an air temperature in a range of 50-70℃ with an air flow of 0.66 m/s. Sliced jujubes did not exhibit a constant-rate drying period and all the drying operations are seen to occur in the falling rate period. At the beginning of drying process, drying rate was very high, and drying rate continued to decrease as moisture content approached to equilibrium moisture content. It is apparent that drying rate decreases continuously with decreasing moisture content or increasing drying time. It is also noted that the drying rate increased with the increase in drying air temperature. The drying rate was more for jujube slices dried at higher temperature than the ones dried at lower temperature for the same average moisture content of the sample. Consequently, the drying time decreased at a higher drying air temperature condition. Moisture transfer from jujube slices was described by applying the Fick's diffusion model and the effective diffusivity changed between 1.354×10-10 and 2.787×10-10 m2/s within the given temperature range. Effective diffusivity increased linearly with increasing temperature. An Arrhenius relation with activation energy values of 33.22 kJ/mol for jujube slices by hot-air drying expressed the effect of temperature on the diffusivity.

Dehydration is the one of the simplest ways to improve the shelf-life of fruits and vegetables by reducing the moisture content. Dehydration operations are important steps in food processing industry, which involves a process of moisture removal due to simultaneous heat and mass transfer. Drying provides a longer shelf-life to the food, cheaper transportation cost, and smaller space demand during storage. Hot-air drying of hamcho pieces were carried out to compare the influence of blanching at 90℃ for 5 min as a pre-treatment on the drying kinetics at temperatures of 50℃, 60℃, and 80℃ at a constant airflow velocity of 0.66 m/s. The pretreatment had significant effects on the moisture content of the hamcho samples. In all the drying temperature selected, the blanched samples had shorter drying time than the control. Based on these comparisons it is seen that blanching treatment prior to drying could improve the drying kinetics of hamcho samples at all drying temperatures. The activation energy was calculated by plotting the natural logarithm of drying rate constant (k) versus the reciprocal of the absolute temperature. It turned out to be 36.90 and 30.76 kJ/mol for the control and blanched sample, respectively.

본 연구에서는 서로 다른 열전달 특성을 가진 탄소섬유 전기발열체와 경유온풍난방기가 온실 내부의 온습도, 에너지소비, 작물생육 등에 미치는 영향을 분석하기 위해 오이 재배 단동온실에 대한 난방 비교시험을 수행하였다. 전기발열체 온실에서 난방용량이 온실 환경과 난방기 운전에 미치는 영향을 분석하기 위해 온실에 6, 9, 16kW의 전력을 각각 공급한 결과 전기발열체 ON-OFF 주기는 각각 9, 11, 15회로 비례하여 증가하였으며 온실 내부 평균온도는 각각 15.2, 15.3, 15.6oC, 평균상대습도는 84, 81, 76%로 나타나 난방 용량이 클수록 온실내부 온도는 높고, 상대습도는 낮게 나타났다. 또한 6, 9kW 가동 시 하부온도가 상부보다 0.1oC 높았으며 16kW 가동 시는 상부 평균온도가 하부보다 0.2oC 높았다. 전기발 열체와 경유온풍난방기의 비교 시험에서는 난방 시 온실 상부와 하부의 온도차가 전기발열체 온실이 0.1~0.2oC로 경유온풍난방기 온실의 0.5~0.6oC보다 작았으며, 온실 상류와 하류의 온도차는 전기발열체 온실이 0~0.1oC로 경 유온풍난방기 온실의 1.3~1.4oC보다 작아 정밀한 온도관리가 가능하였다. 난방기간 동안 사용한 에너지사용량은 경유온풍난방기 온실이 경유 867L를, 전기발열체 온실이 전력량 8,959kWh를 사용하였으며, 난방비용은 각각 607 천원과 403천원이 소요되어 전기발열체 온실에서 약 34%의 비용절감 효과가 있었다. 전기발열체 온실의 경우 상대적으로 군락 상하부의 환경관리가 균일하여 초장을 비롯한 전반적 생육상황이 경유온풍난방기 온실보다 좋았으나 통계적으로 유의한 차이는 없었으며, 수확량 역시 전기발열체 온실의 작물군락 하부 온도가 경유온풍 난방기 온실보다 1.3oC 더 높게 관리되어 4.3% 증수효과가 있었으나 통계적으로 유의한 차이는 없었다. 원예 시설의 최적 난방 관리를 위해서는 각 난방기의 열전달 특성에 기초하여 난방기 용량, 배치, 열분배 방법에 대한 설계가 요구되며, 전열선 형태의 난방기 역시 작물형상 및 재배방법을 고려하여 전열선의 개수, 위치, 방열 온도 등에 대한 설계가 필요한 것으로 판단되었다.

The effect of drying temperature and steaming time on the browning and antioxidant activity of dried Platycodon grandiflorum was investigated. Thirteen treatment conditions were constructed using central composite face-centered design containing 5 center points. Drying temperature and steaming time (as factors) were 45-75oC and 15-45 min. According to treatment conditions, dried Platycodon grandiflorum was assessed for color characteristic, degree of browning, total polyphenol content, and DPPH and ABTS free radical scavenging (as responses). When increasing drying temperature within a given steaming time, dried Platycodon grandiflorum exhibited decreased lightness, increased redness, degree of browning, and total polyphenol contents, and enhanced antioxidant activities. Except for total polyphenol contents and antioxidant activities, steaming time within a given drying temperature exhibited similar effects to those observed in drying temperature. However, steaming time did not likely influence total polyphenol contents and revealed the opposite trends observed for the effect of drying temperature on their antioxidant activities. The overall results suggested that drying temperature was the main factor for changes in the browning and antioxidant activity of dried Platycodon grandiflorum.

The effects of drying temperature on the drying characteristics of soybeans at the different position in the dryer with 28.1% (±0.8) of initial moisture content were studied. Drying temperatures varied at 35, 45 and 55ºC, with a constant inlet air velocity (3 m/s). The local air velocities at a position 1, 5, and 9 were 0.150 m/s (±0.012), 0.247 m/ s (±0.018) and 0.795 m/s (±0.036), respectively. The drying rate increased as the local air velocity increased from 0.150 m/s to 0.795 m/s. The cracked grain ratio increased as the drying rate increased. To prevent quality degradation of soybeans during hot-air drying, the local air velocity should be considered. Thin-layer drying models were applied to describe the drying process of soybeans. The Midilli-Kucuk model showed the best fit (R2>0.99). Based on the model parameters, the drying time to achieve the target moisture content (15%) was successfully estimated. The drying time was strongly dependent on the position in the dryer and the drying temperature.

This study was performed as the preliminary research to calculate the concentration of radon exposure and the annual effective dose in public hot spring bath-house. The research found that public bathhouses are the primary cause of the indoor air radon concentration inside a hot spring bathhouse. The indoor radon concentration inside a bathhouse differs significantly by region and among bathhouses in the same region, indicating that the indoor air radon concentration is affected by many factors. The annual effective indoor radon dose by exposure is estimated to range from 1.2×10−2mSv/y to 2.5×10−2mSv/y. Since this research is considered as preliminary research, further and additional relevant research to more reliably calculate the result are necessary, including accumulative research for indoor radon concentrations, and research for exposure coefficients such as the behavior patterns of public bathhouse users, etc.