• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.1
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• pp.118-127
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• 2014

This study was investigated to compare the physicochemical properties between hot air dried ramie leaf (HR) and freeze dried ramie leaf (FR). There were no significant differences in moisture, crude protein, crude fat, crude ash, and carbohydrate content depending on the drying methods, but the dietary fiber content was significantly higher in FR than in HR. The major amino acids were aspartic acid, glutamic acid, and leucine, and the contents of total amino acids, total essential amino acids, and essential amino acid ratios were higher in FR compared with HR. Major fatty acids were linoleic acid, palmitic acid, arachidic acid, and linolenic acid. Hot air drying caused a decrease in unsaturated fatty acids and an increase in saturated acids; however, there was no significance difference between the two different drying methods. The contents of vitamin A, E, and C in FR were higher than those in HR, and there were significant differences in the contents of vitamin A and C depending on the drying methods. Regardless of the drying methods, both HR and FR were abundant in order of Ca, K, Mg, Mn, Fe, Na, and Zn. The contents of total minerals, total organic acids and total free sugars in HR were significantly higher than those in the FR.

• Korean Journal of Food Science and Technology
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• v.33 no.2
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• pp.245-251
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• 2001

This research was conducted to study the changes in physical characteristics of mushrooms (Agaricus bisporus) as influenced by drying methods. Samples were dried using either hot air drying, vacuum drying, or freeze drying and changes in the color, browning index, hardness and rehydration rate were evaluated by response surface methodology. Hot air drying resulted in the fastest drying of sample as compared to other methods. The rate of drying was most affected by the environmental temperature rather than air velocity or vacuum pressure. The overall color difference increased as the temperature and air velocity increased. The overall color changes of the freeze dried samples were minimal as compared to those of fresh mushrooms. The hot air dried samples showed the greatest changes in the overall color, browning index as well as hardness. The freeze dried samples showed the best rehydration characteristic and maintained the best overall quality after drying.

• Food Science and Preservation
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• v.6 no.3
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• pp.319-323
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• 1999

This study was conducted to minimize the deterioration of dried kiwifruit quality. Osmotic dehydration was carried out as pretreatment before drying. After the kiwifruits were pretreated under optimized osmotic dehydration conditions, they were dried by three drying methods(hot air drying, vacuum drying, freeze drying). Hot air drying and vacuum drying were superior to freeze drying in the drying speed. But vacuum and freeze drying preserved more vitamin C than hot air drying. Also, osmotic dehydrated kiwifruit kept better quality than nontreated kiwifruit. Diffusion coefficient which describes moisture transfer, was high in drying process pretreated with osmosis. The changes of vitamin-C followed the second-order reaction rate equation with high RE, respectively.

• The Journal of Natural Sciences
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• v.15 no.1
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• pp.97-109
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• 2005

This experiment was established to find out the effect of drying methods on the fruit and powder color of red pepper. Hunter's L, a, and b values of the dried fruit were also higher with the cut fruit in comparison with the whole or punched fruit. The Hunter's a value of the pepper powder after drying and grinding was slightly higher for the whole fruit with sun drying, but it was higher for the cut fruit in case of heat drying. The ASTA value was higher when pepper fruits were sun dried. For the heat drying, the value was higher with the drying temperature $60^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.258-258
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• 2013

최근 건조 제품의 양질화, 고급화 및 편의화가 요구되어 이를 충족시키기 위한 새로운 건조방법이 계속 개발 되어 왔다. 이러한 방법들 중에서 저온과 진공하에서 건조가 이루어지는 진공 동결 건조는 가장 완벽한 건조 방법으로 최근 실용화 되고 있다. 진공동결건조란 건조의 한 종류로 수분을 함유한 시료를 동결시킨 후 진공펌프를 이용하여 수증기압을 3중점 이하로 낮추어 얼음을 직접 증기로 만드는 승화의 원리에 의해서 얻어진다. 분무진공동결건조의 특징은 (1) 물리적구조의 보존성, (2) 화학적인 안정성, (3) 생물학적인 활동의 보존성, (4) 제품의 높은 복원성 및 재생성이다. 따라서 분무진공동결건조 기술은 크게 진공, 분무, 동결, 건조, 멸균 등과 같은 요소기술의 복합기술이라 할 수 있다. 분말을 제조하기 위해서 진공동결건조 후 분쇄하는 방법을 사용하나 본 방법에서는 정밀화학품 제조를 위해서 분무진공동결건조 방식을 사용한다. 이를 통하여 적당한 크기인 5~10 um의 입경 제조가 가능하고, 공기동력학적인 입경이 기존 방식에 비해 작아서 허파까지의 운반효율이 1.5~2배 우수하다. 화학, 의학 분야에서의 분무동결 건조는 주로 민감한 제품, 즉 생물학적 고유성의 손상 없이 물을 제거하는데 사용되어 영구적으로 저장 가능한 상태로 보관할 수 있으며 물의 첨가로 원상태로 복구할 수 있어서 매우 각광을 받고 있다. 의약용 냉동건조 제품은 항생물질, 박테리아, 혈청, 백신, 검사 약물, 단백질을 포함하는 생물공학 제품들, 세포, 섬유, 화학제품 등이 있으며 주로 vial 또는 ampule 상태로 건조가 이루어진다.본 연구에서는 원료를 $-194^{\circ}C$의 액체질소에 분무시켜 동결된 미립자를 형성한 후 진공 및 저온상태에서얼음의 승화(sublimation)에 기반한 1차 건조와 수증기 탈착(desorption)에 기초한 2차 건조 과정으로 구성된 분무진공동결건조기를 개발하였다. 분무동결 과정의 해석을 통해 2유체식 노즐을 통해 분무된 미세 입경의 액적이 액체 질소 표면까지 도달하는 회수률, 분무 노즐의 위치, 운전 조건 및 용기의 설계의 최적화를 수행하였다. 초기 액적속도, 분무노즐의 높이, 흡입구 추가에 따른 액적 유동 및 회수의 특성을 제시하였으며 이를 통한 분사시스템 고도화 가능성을 제시하였다. 구형의 미세 입자가 적층된 제품의 동결건조 공정의 해석은 흡착승화 모델(sorption sublimation model)을 기반으로 다음과 같은 열전달, 물질전달, 상변화 모델을 고려하여 유도되었다. 분무노즐 및 냉동/진공 배기계 시작품을 개발하여, 표면의 고다공도를 갖춘 입경 3~20 m 정도의 시료를 얻을 수 있으며, 동역학적 입경 5 m 충족함을 확인하였다.

• Korean Journal of Food Science and Technology
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• v.41 no.1
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• pp.64-68
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• 2009

The effects of drying methods (hot air, cold air, vacuum, and infrared drying) on physicochemical and organoleptic qualities of sliced-dried persimmons (Diospyros kaki Thumb. cv. Cheungdobansi) were investigated. The weight of the sliceddried persimmons ranged from 9.30 to 12.01 g, the length from 3.55 to 4.06 cm, the width and thickness were from 3.17 to 3.73 cm and 1.82 to 2.04 cm, respectively. Hot air drying resulted in the highest hardness value as well as Hunter's L, a, and b values. Infrared drying showed the lowest L value and vacuum drying revealed the lowest a and b values. Moisture contents of the sliced-dried persimmons ranged from 38.04 to 46.41%, and soluble solid contents were 42.96-$48.44^{\circ}Bx$. The phenolic compounds and DPPH radical scavenging activity were high for infrared and vacuum drying methods, and all the sliced-dried persimmons showed relatively high antioxidant activities. The sensory evaluation results indicated that the organoleptic scores for the overall preference were high in the order of vacuum > infrared > hot air > cold air drying. These results suggest that the drying methods affected the qualities of the sliced-dried persimmons, showing that vacuum drying is the mast effective among the methods tested for manufacturing the high-quality sliced-dried persimmons.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.173.2-174
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• 2003

국내 보급되고 있는 곡물건조기는 열풍형 순환식 곡물건조기가 주종을 이루고 있는데, 이건조기의 경우 곡물이 순환하면서 열풍공급과 템퍼링과정을 반복하면서 건조가 이루어지는 대류열전달 방식을 채택하고 있다. 대류열전달 방식은 복사열전달 방식에 비해 열전달률이 낮기 때문에 건조속도와 열효율이 떨어지며, 건조시 미질 향상과 건조비용 절감에 한계가 있어 왔다. 따라서 건조에너지의 절감과 동시에 고품질 쌀 생산을 할 수 있는 새로운 형식의 곡물건조기술을 확립하고자 원적외선 곡물건조기를 개발하였다. 원적외선은 0.56~l,000$\mu\textrm{m}$의 전자파로서 세라믹 도료표면에 열을 가하면 원적외선 파장대의 강한 에너지를 얻을 수 있다. 이같은 원적외선 에너지를 농산물에 조사시키면 열이 침투하게되고 동시에 농산물의 내부온도가 상승함에 따라 활발한 분자운동을 하면서 수분을 표면으로 이동시키기 때문에 열풍건조방법에 비해 열전달효율이 높고, 농산물을 보다 균일하게 건조가 가능하므로 좋은 품질의 쌀을 생산할 수 있는 특징을 가지고 있다. 시작기는 1회 3,800kg을 건조할 수 있도록 설계하였고, 템퍼링실, 건조실, 열풍실, 승강기 등으로 구성되었다. 원적외선 방사체의 형태는 실린더형이고, 방사체가 설치된 열풍실 위쪽은 타공망, 아래쪽은 방사량을 높이기 위하여 일부 개방된 구조로 제작하였다. 본 연구에서 구명된 원적외선 방사체 길이와 조사거리는 각각 1,470mm, 125mm가 적절한 것으로 나타났다. 시작기의 성능시험을 열풍건조기(대비구)와 비교한 결과 소음은 대비구에서의 94.12dB보다 13% 가량 낮게 나타났고, 건조온도를 45$^{\circ}C$로 설정하고 벼를 건조했을 때 건감률 0.58%,wb로 대비구의 0.47%,wb 보다 23% 높았고, 건조소요에너지도 470kcal/kg - water로 2%의 절감되었다. 또한 건조한 벼를 도정하여 색, 냄새, 윤기, 찰기 등에 대한 관능검사결과는 원적외선 건조방법이 종합기호도가 6.37으로 열풍건조방법 6.13보다 우수한 평가를 받았다. 건조비용은 시작기의 구입가격이 20% 비싸기 때문에 시간당 고정비가 높았으나, 건조성능이 우수하여 건조비용이 69,350원/톤으로 대비구보다 14% 절감되는 것으로 나타났다.

• Korean Journal of Food Science and Technology
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• v.30 no.1
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• pp.103-109
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• 1998

For the purpose of improving quality of dried anchovy, raw anchovies after hot air drying were subjected to six different processes: 5 min microwave and 1 min holding-12 times (MW5), 10 min microwave and 1 min holding-6 times (MW10), 5 min microwave with hot air and 1 min holding-12 times (MWH5), 10 min microwave with hot air and 1 min holding-6 times (MWH10), 5 min microwave vacuum and 1 min holding-12 times (MWV5), 10 min microwave vacuum and 1 min holding-6 times (MWV10) at 100 Watt and 2450MHz. There were no significant effects of different processes on water content, pH, color, acid value and volatile basic nitrogen. The sum of fatty acids on commercial anchovy occupied 38.34% of saturates 22.91% of monoenes and 22.91% of polyenes and dried anchovies subjected to microwave processes had similar compositions. Dominant fatty acids were palmitic acid and docosahexaenoic acid in each process. Among the free amino acids, alanine, arginine, lysine and leucine were dominant in all processes. Dried anchovies showed little significant differences in texture in all processes. Sensory evaluation data showed that the quality of dried anchovy subjected to microwave process was acceptable and microwave vacuum process was the most desirable one.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.8
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• pp.1242-1248
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• 2013

This study was performed to determine the effects of pretreatment (NT: non-treatment, BTS: boiling treatment with 3% sodium chloride, DTG: dipping treatment in glycerol) and drying methods (sun drying, hot air drying, and cold air drying) on the physicochemical properties and antioxidant activities of dried jujube (Zizyphus jujuba Mill.) fruits. Our results show that moisture content is lower (P<0.05) with DTG, and that moisture content is lower with hot air drying compared to other drying methods. The bulk density was highest with BTS. The soluble solids content was highest with DTG. Additionally, the soluble solids content were highest in the following order: hot air drying> cold air drying> sun drying. The titratable acidity of hot air drying was highest of all the drying methods. The titratable acidity was higher with NT and DTG, and the brix and acid ratio of sun drying was higher than other drying methods. Among the drying methods, BTS showed the best browning-retarding effect, whereas boiling treatment affected quality and color. The total polyphenol content from hot air drying and NT or DTG treatment was relatively higher than the content from BTS. The flavonoid content was highest with BTS, and all dried jujube showed relatively high antioxidant activities. The sensory evaluation results indicated that the organoleptic scores for overall preference were higher in the NT and DTG treatment groups. These results suggest that pretreatment and drying methods affect the quality of dried jujube fruit, and show that glycerol treatment with hot air drying can be applied to the production of high quality dried jujube.

• Food Science and Preservation
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• v.19 no.4
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• pp.485-491
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• 2012

This study was conducted to investigate the pH, soluble solid contents, color difference, mineral contents, free sugar contents, and sensory quality of infrared- and cold-air-dried peaches. The pH, soluble solid contents, and free sugar contents of the infrared-dried peaches were higher than those of the cold-air-dried peaches. In the Hunter's color value, the L and ${\Delta}E$ values of the infrared-dried peaches were higher than those of the cold-air-dried peaches; but the a and b values of the cold-air-dried peaches were higher than those of the infrared-dried peaches. The major organic acids of the dried peaches were citric acid, malic acid, and oxalic acid. The minerals with the highest to lowest contents, in that order, were K, Mg, Ca, Na, Fe, Zn, Cu, and Al. The mineral contents of the cold-air-dried peaches were higher than those of the infrared-dried peaches. The appearance and taste of the infrared-dried peaches were better than those of the cold-air-dried peaches. These results indicate that infrared drying is the effective drying method for the production of high-quality dried peaches.