• Food Science and Biotechnology
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• 제14권5호
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• pp.661-666
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• 2005

The specific objectives of this study were to dry yam chips using microwave vacuum drying, freeze drying and hot air drying, then to coat the dried yam chips with ascorbic acid cocrystallized sucrose, and finally to compare the quality of yam chip snack foods with respect to drying and coating characteristics. The microwave vacuum dried sample showed the highest drying rates and much less surface damage than the hot air dried one did. The shape and color of the microwave vacuum dried/coated sample were allocated between those of the freeze dried/coated sample and the hot air dried/coated sample. The freeze dried/coated sample scored excessively low in organoleptic hardness and chewiness to be suitable as a snack. The hot air dried/coated sample was too deep in color, wrinkled, excessively high in organoleptic hardness and chewiness, and excessively low in mouthfeeling. Therefore, the microwave vacuum dried/coated sample presented the best overall attributes as a snack, with respect to organoleptic characteristics, shape, color, and drying rates.

• 한국식품과학회지
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• 제31권5호
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• pp.1337-1344
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• 1999

본 연구에서는 난백분말과 카제인 기질에 생육촉진물질을 첨가하여 만든 젖산균 발효식품의 동결건조에 의한 젖산균 생균수의 변화, 관능성의 변화, 경도, 휘발성 향기성분의 변화를 관찰하였다. 동결 또는 동결건조에 의하여 젖산균 발효식품의 pH 거의 변화가 없으나, 생균수는 동결, 특히 동결건조 도중에 급격히 감소하였고, 동결 전의 균수를 I00%로 했을 때, 동결 후의 생존율을 $72.0{\sim}82.4%$, 동결건조 후의 생존율은 $10.0{\sim}20.4%$였다. 동결건조 전 시료와 동결건조-환원된 시료의 관능성을 비교하여 보면, 대체적으로 동결건조 전의 시료가 동결건조-환원된 시료보다 관능성이 우수하였으나, 동결건조시킨 고체상의 발효유 및 젖산균 발효식품도 환원성이 뛰어나고 기호도가 양호하였다. 동결건조 전의 젖산균 발효식품과 동결건조-환원된 젖산균 발효식품의 휘발성 향기 성분의 변화를 보면, 동결건조에 의하여 모든 시료의 휘발성 향기 성분의 함량이 감소하는 경향을 보였고 그 감소 정도는 시료 별로 차이가 있었다.

• 한국식품위생안전성학회지
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• 제18권4호
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• pp.243-250
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• 2003

S-methylmethionine, vitamin U levels were affected by cultivars, parts fo Korean Chinese cabbages, and drying methods. Among drying conditions, freeze drying method appeared the best condition to maintain bitamin U content compared to oven and air drying methods. In the case of KOrean Chinese cabbages, outward leaves have high levels of chlorphyll and fiber. From this study, the outward parts contained high levels of vitamin U in two cultivars. Leaf parts were 1.1-21.2 times higher in vitamin U levels than midribs in both cultivars. This difference was shown most distinctively in freeze dried outward parts of Winter Pride cultivar. Like vitmnin U, fee amino acids also showed much higher levels in leaves. Levels of amino acids showed irregulatoy changing patterns at different parts and cultivar of Korean Chinese cabbages with various drying methods, Alanine and threonie appeared relatively aboundant amino acids in most parts of samples. Since no distinctive trends were observed in this rsult, it seems no relationship exists between amon oacids and bitamin U levels. Levels of methionine in differnent parts and cultivars of Korean Chinese cabbages dried with various methods did no show clear relationship with tlevel of vitamin U. Moreover, emthionine was not detected in freeze dired outward leaf parts which were the hithest parts of vitamin U levels in Winter Pride and 55 days cultivar. There were simila levels of methionine between overn and freeze drying. Samples prepared by air drying showed significatly lower levels than those by oven and freeze dryting. Methionine as aprecursor of vitamin U, may play a role in an increase of vitamin U during drying of KOrean Chinese cabbages.

• 한국축산식품학회지
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• 제18권2호
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• pp.176-184
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• 1998

The objective of this study was to investigate the effects of freezing rate on aroma retention and to examine the mechanism of aroma retention during freeze drying process. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80${\times}$20mm) containing diacetyl(2mg/ml) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\circ}C$ and followed with freeze-drying. Under the upper conditions we measured freezing rate and the change of temperature and pressure during freeze drying. Freeze-dried gelatins were cut horizontally into 5 mm thickness from the bottom measured and diacetly contents. Besides, we observed the effect of the relative humidity of the diacetyl contents freeze-dried gelatin during storage. The retained diacetyl content was increased at high freezing temperature and in order of 0∼5, 5∼10, 10∼15, 15∼20 mm section from the bottom of the sample. It was observed that the retained diacetyl content was high in 15∼20 mm section. The retained diacetyl content and freeze-dried gelatin stored in the condition of high relative humidity was decreased significantly but in the low relative humidity case, was it decreased in small amount. The results of our experiment resents that the low temperature freezing and low humidity storing condition is effective for preserving aroma compound in food.

• 한국식품저장유통학회지
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• 제6권3호
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• pp.319-323
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• 1999

본 연구는 키위를 이용하여 새로운 가공식품을 개발하고자 삼투건조로 전처리하여 열풍, 진공, 동결건조한 후 삼투처리 유무에 따라 각각의 품질특성을 비교 평가하였다. 수분함량은 무처리 및 삼투처리한 키위를 열풍 진공, 동결건조 하였을 때 무처리가 삼투처리한 경우 보다 낮았다. 건조방법에 따른 vitamin C의 함량은 무처리보다 삼투처리가 낮았으며 건조시간에 따른 vitamin C의 함량변화는 동결, 진공건조시 완만한 감소를 보이는 반면 열풍건조한 경우는 많은 감소를 보였다. 수분의 이동을 나타내는 확산속도는 무처리의 경우 열풍건조가 가장 빨랐으나 삼투처리 후에는 진공건조가 가장 빠르게 나타났다. 세 가지 건조방법 모두 삼투처리가 빠른 건조 양상을 보여 효과적인 전처리 방법임을 확인 할 수 있었다. 품질변화 특성은 열풍, 진공 동결건조 모두 2차 반응속도식이 품질변화예측 모델식으로 적합한 것으로 나타났다.

• 연구논문집
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• 통권22호
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• pp.141-150
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• 1992

A basic study on the batch type freeze dryer has been carried out. The operating principles, merits and demerits of the freeze dryer were described. And the kinds of major components and their roles were also invesigated. As a fundamental study, using the Differential Scanning Calorimeter(DSC), the determination of unfrozen water in the specimens and invesigation of effects of cooling rate on the freeze drying were performed. To provide a guidline of basic design for a freeze dryer, a parametric study about the drying conditions was carried out.

• 한국식품영양과학회지
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• 제36권3호
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• pp.342-347
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• 2007

건조방법을 달리하여 양파분말을 제조하고 건조방법에 따른 양파분말의 물리적 특성을 비교하였다. 건조 양파의 수분함량은 열풍건조한 양파가 13.29%, 동결건조 양파는 12.99%, 진공건조 양파는 10.78%로 나타났고, 조회분 조지방 조단백의 함량은 건조방법에 따라 유의적 차이를 보이지 않았다. 총당 함량은 열풍건조>진공건조>동결건조 순으로 나타났다. 양파분말의 색도는 갈변현상의 영향을 받아 밝기와 황색도에 큰 변화가 있었다. 높은 온도에서 건조한 진공건조 분말과 열풍건조 분말의 Hunter-L값은 낮은 온도에서 동결건조시킨 분말에 비해 매우 낮게 나타났다. 갈변도는 고온처리과정이 없는 동결건조 분말의 경우 가장 낮았으며, 같은 고온에서 건조시킨 진공건조 분말과 열풍건조 분말 간에는 유의적인 차이가 없었다. 주사전자현미경 촬영 결과 양파분말의 입자크기가 열풍건조>진공건조>동결건조 순으로 나타났고, 급속 동결한 후 낮은 온도에서 수분을 승화시켜 건조하는 동결건조 양파분말의 공극률이 가장 크게 나타났다. 양파분말의 복원력은 입자크기가 제일 큰 열풍건조 분말이 가장 높았고, 다음으로는 진공건조, 동결건조 분말의 순으로 나타났다. 용해도는 동결건조 분말이 다른 두 방법에 비해 높았으며, 팽윤력은 열풍건조 분말이 가장 높았다. 비타민 C의 함량은 온도의 영향을 적게 받은 동결건조 분말이 가장 높았으며, 총 폴리페놀 함량은 진공건조>열풍건조>동결건조 순으로 나타났다.

• 한국재료학회지
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• 제26권6호
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• pp.320-324
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• 2016

Porous SiC beads were prepared by freeze-drying a polycarbosilane (PCS) emulsion. The water-in-oil (w/o) emulsion, which was composed of water, PCS dissolved p-xylene, and sodium xylenesulfonate (SXS) as an emulsifier, was frozen by dropping it onto a liquid $N_2$ bath; this process resulted in 1~2 mm sized beads. Beads were cured at $200^{\circ}C$ for 1 h in air and heat-treated at $800^{\circ}C$ and $1400^{\circ}C$ for 1 h in an Ar gas flow. Two types of pores, lamella-shaped and spherical pores, were observed. Lamellar-shaped pores were found to develop during the freezing of the xylene solvent. Water droplets in the w/o emulsion were changed into spherical pores under freeze-drying. At $1400^{\circ}C$ of heat-treatment, porous SiC was synthesized with a low level of impurities.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.287-288
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• 2006

Two approaches for the fabrication of tailored powder composites with specially distributed pore-grain structure and chemical composition are investigated. Electrophoretic Deposition (EPD) followed by microwave sintering is employed to obtain functionally graded materials (FGM) by in-situ controlling the deposition bath suspension composition. $Al_2O_3/ZrO_2$ and zeolite FGM are successfully synthesized using this technique. In order to fabricate an aligned porous structure, unidirectional freezing followed by freeze drying and sintering is employed. By controlling the temperature gradient during freezing of powder slurry, a unidirectional ice-ceramic structure is obtained. The frozen specimen is then subjected to freeze drying to sublimate the ice. The obtained capillary-porous ceramic specimen is consolidated by sintering. The sintering of the graded structure is modeled by the continuum theory of sintering.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1321-1326
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• 2008

A study on the heat and mass transfer for the drying time in spray freezing drying process was experimentally presented in this paper. A spray freezing dryer for the production of an inhalable powder medicine is developed and an albumin solution as protein specimen is adopted. The freeze-drying for the albumin solution is tested in three different height of the particles piled up in a tray such as 2 mm, 5 mm, 7 mm, and the drying time is estimated as 10 h, 15 h, 22 h. From this results, the correlation is suggested and the drying time with various height of the particles piled up in a tray can be estimated. The assessment on the drying time is conducted thought a microbalance and the rate of water content is measured. The results based on temperature and weight are compared. The difference of the results happens due to the heat transfer from the lateral side of the vial. It is thought that the better estimation in drying time can be predicted by considering the heat transfer effect.