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.

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.

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.

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.

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.

To know proper drying condition for making a safe Sunsik, uncooked food, microbial and physicochemical characteristics of cereal dried by hot-air drying was investigated. As moisture content of 3 Sunsik samples was reduced to about 8%, protein, carbohydrate, fat and ash content of those was increased. But approximate composition of black bean, black rice and glutinous millete and black bean showed little changes during hot-air drying (30, 40, 50oC). Lightness (L value), redness (a value) and yellowness (b value) was increased after hot-air drying. In case of black rice and glutinous millet, b value and L value wasn't changed individually. When we measured a texture for 3 kinds of raw cereal for, hardness of dried cereals was lower than raw cereals. Hardness of dried cereals was increasd as drying temperature was increased. As results of mocrobiologicl experiment for 3 kinds of sunsik on hot-air drying conditions, total cell count was reduced 2 log - 3 log and other pathogenic microorganism wasn't detected except B. cereus.

The principal objective of this study was to assess the antioxidative activities of Petasites japonicus against oxidative stress in bovine brain tissue . Petasites japonicus is found with a relatively widespread distribution, and is cultivated as a culinary vegetable in Korea. Petasites japonicus samples were dried either by freeze-drying or by hot air-convection drying (80℃), then evaluated for their antioxidative activity by measuring 1-dipheny-1，2-picrylhydrazyl (DPPH) radical scavenging, and by measuring thiobarbituric acid-reactive substances (TBARS) in brain homogenates subjected to Fe2+ -mediated lipids with or without the addition of botanical extract. Hot air convection-drying resulted in a slight increase in the extraction yie1d as compared with freeze-drying. However, total phenol and flavonoid contents in freeze-dried Petasites japonicas were significantly higher than those of hot air convection-drying. Freeze-drying increased the free radical scavenging activity of Petasites japonicas, leaves, and stems by 52.6, 28.6, and 248.0%, as compared with hot air convection-drying. Additionally, the IC50 values measured by TBARS in hot air convection-dried Petasites japonicas， leaves, and stems were increased by 36.0, 31.6, and 15.9%, as compared to those of freeze-drying. Although antioxidative activity was reduced slightly by heat processing in Petasites japonicas, freeze-drying for each portion of Petasites japonicus was the most appropriate for use as a functional food and pharmaceutical material.

도토리의 산업적 활용도 제고를 위해 도토리차를 제조하였으며, 증숙, 건조 전처리에 따른 도토리차의 품질특성 및 항산화 활성을 연구하였다. 색도는 명도와 황색도의 경우 열풍 건조 볶음한 도토리차에서 높은 값을 나타내었으며, 적색도의 경우 전처리 없이 볶음한 도토리차에서 높았다. pH는 증숙 및 열풍 건조 공정 처리에 따라 감소하는 경향을 나타내었으며, 탁도 또한 감소하는 결과를 나타내었다. 전처리를 실시한 도토리차에서 총당 함량이 전체적으로 증가하였으며, 총 폴리페놀 및 플라보노이드 함량 또한 증가하였다. 도토리차의 DPPH 및 ABTS 라디칼 소거능 평가를 실시하였으며, 열풍 건조 후 볶음한 도토리차에서 가장 높은 라디칼 소거능을 나타내어, 증숙 공정 처리군보다 열풍 건조 공정 처리군에서 우수한 활성을 나타내는 것으로 나타났다. 도토리차의 기호도 평가에서는 열풍 건조 후 볶음한 도토리차가 맛, 향, 종합적 기호도에서 가장 높은 값을 나타내었다. 이러한 결과를 종합하여 볼 때 전처리 공정을 통한 도토리차 제조가 제품의 품질특성 및 항산화활성 증진에 긍정적인 영향을 미치며, 특히 열풍 건조 후 볶는 방법을 이용하였을 때 높은 품질특성, 항산화 활성 및 기호도 평가를 나타내는 것으로 판단된다.

The present study was undertaken to determine the changes of physicochemical and antioxidant activity using leaf and root in hot air-dried Allium hookeri (HA) and freeze-dried Allium hookeri (FA). The leaf of HA was higher level of moisture and crude fat compared with those of the leaf of FA. The crude fat content in root of HA was higher than that in FA. However, moisture, crude ash, crude protein and carbohydrate did not show any differences between two different drying methods. The organic acid contents of Allium hookeri root including oxalic acid, citric acid, tartaric acid, malic acid, succinic acid, lactic acid, formic acid, acetic acid showed the differences between hot air-drying and freeze-drying methods. The major minerals were Ca, K and Mg, which were higher level of the leaf of HA compared with those of FA. The leaf of HA showed the highest vitamin C content (801.65 mg/100 g). The content of vitamin E in the leaf of FA was higher than that of HA. The contents of total polyphenol and total flavonoid in the FA leaf were higher than that in HA. The DPPH radical-scavenging activity in leaf of HA (65.73%) was significantly higher than that of FA (57.73%).

고구마 잎을 건조 채소화 하기 위한 기초자료를 제공하 기 위해서 열풍건조한 고구마 잎 메탄올 추출물에 함유된 총 탄닌, 총 플라보노이드, 총 폴리페놀 함량을 분석하고, 항산화 효과로 DPPH 라디칼 소거활성, ABTS 라디칼 소거 능, 아질산염 소거능 등을 분석 비교 검토하였다. 총 탄닌 함량은 신미 40℃에서 10.87 mg/g, 70℃에서 7.28 mg/g으로 감소되었고, 총 플라보노이드는 하얀미 40℃에서 55.37 mg/g, 70℃에서 39.63 mg/g으로 감소되었다. 즉 저온건조가 고온건조보다 이들 물질의 함량이 많았다. DPPH 라디칼소 거 활성은 신미와 하얀미 40℃에서 84.33%와 85.25%로 가 장 높았으며, ABTS 라디칼 소거능도 40℃ 처리구에서 80% 가 넘는 높은 값이었다. 아질산염 소거능은 신미와 하얀미 가 40℃에서 76.15%와 73.74%로 가장 높았고 70℃에서는 낮았다. 품종 간에는 하얀미가 신미보다 페놀성 물질과 항 산화 물질이 더 많은 것으로 나타났다. 즉 건조한 고구마 잎의 항산화 효과는 품종간의 차이는 있었으나, 40℃ 시료 에서 높고, 70℃ 시료에서 낮았다. 이는 건조온도에 의해 영향을 받는 것으로서 낮은 온도에서 건조하는 것이 유효성 분의 감소가 적어 항산화 능력이 높은 결과이었다.

본 연구에서는 국내에서 잘 이용되지 않는 고구마 잎을 열풍건조하여 이들의 건조속도와 수화복원력을 조사하고, 일반성분, lutein 과 β-carotene 및 색도 등을 분석 비교 검토하여 고구마 잎의 건조 채소화를 위한 기초자료를 제공하고자 하였다. 품종 간의 차이는 있었으나 온도가 높을수록 건조속도가 증가해 70℃에서 건조속도가 가장 빠르며, 60℃, 50℃, 40℃ 순서로 건조시간이 많이 소요되었다. 일반성분은 생엽에서 수분 87~88%로 많았으나 열풍건조 후 6~8% 이었다. 다른 일반성분은 온도별에 따른 유의적인 차이는 없었다. 기능성 성분인 lutein 함량은 신미 40℃에서 171.59 μg/g 많았으며, 하얀미 70℃에서 73.75 μg/g로 적었다. β-carotene 함량에서 신미가 40℃에서 379.59 μg/g 많고, 하얀미 70℃에서 170.78 μg/g로 적었다. 기능성 물질은 40℃에서 가장 많고 50℃, 60℃, 70℃ 순서로 함량이 감소되었다. 색도는 생잎과 건잎을 비교하였을 때 신미와 하얀미 모두 40℃에서 색이 유지되었으며, 수화복원성에서도 신미와 하얀미 모두 40℃에서 수화복원율이 각각 233.93%, 223.47%로 가장 높았다. 결과적으로 건조 고구마 잎의 품질은 건조시간보다는 온도 영향이 컸으며 저온건조가 상품적 가치가 있는 것으로 판단되었다.