• 한국축산식품학회지
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• 제18권2호
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• pp.164-175
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• 1998

The objective of this study was to investigate the effects of freezing rate on ice crystal size and freeze-drying rate. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80$\times$20mm) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\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 and measured their pore sizes. Also freeze-drying rate(primary drying) is estimated by measuring the temperature of sample and pressure of vacuum chamber. During freeze-drying, profiles of pressure and temperature were shown constant tendency regardless of freezing temperature and we could expect the end-point of freeze drying by considering pressure and temperature together. In temperature profiles, the point which temperature increased significantly was observed during freeze-drying. There is no relationship between freeze temperature and drying rate of primary drying in our model system. As freezing temperature increased, ice crystal size(X*) which correspond to 63.2% of cumulative frequency was increased and at the same freezing temperature ice crystal size(X*) was decreased with distance from the bottom of the sample. Freezing conditions have a strong influence on the quality of the final freeze-dried products in freeze-drying system.

• 설비공학논문집
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• 제2권2호
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• pp.105-111
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• 1990

The drying rate in freeze drying was obtained by experiment of garlic moisture contents depending on the drying time. Freeze drying experiment of garlic juice was carried out in vaccum freeze drier of laboratory scale by backface heating, and a mathematical model is also used to simulate the process of simultaneous heat and mass transfer in freeze drying to compare with experimental data.

• 한국식품영양과학회지
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• 제19권6호
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• pp.555-564
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• 1990

과실쥬스와 같은 자연 생산물의 동결건조에 있어서 가공처리중 휘발성분의 보유력 변화를 알아보기 위하여 headspace gas chromatography 기술의 특징을 이용하여 동결건조 속도, 초기 고형물의 함량 및 압력 등이 어떠한 영향을 미치는가에 대한 실험결과는 다음과 같다. 동결건조 속도가 휘발성분의 보유력에 대한 영향은 현저하였으며, 동결시간이 길수록 뚜렷하였다. 동결 건조 제품에서 휘발성분의 보유력은 동결에 의해 영향을 받았다. 동결건조 조건하에서 가장 많은 휘발성분의 손실은 동결건조 초기단계, 즉 1~2 시간 사이에서 일어났다. 휘발성분의 보유력은 초기 고형물의 함량이 많을수록 높았다. 동결속도가 빠를 때보다는 늦을 때가 휘발성분의 보유력이 높았으며 높은 압력에서보다 낮은 압력에서 높았다.

• 한국연초학회지
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• 제17권2호
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• pp.149-159
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• 1995

The freeze drying rate was investigated under various conditions such as pressure and moisture contents in order to establish the optimum condition for expansion of the culled flue cured tobacco lamina. The optimal pressure in the chamber to maintain the heat and mass transfer was about 0.8torr, When the moisture contents of sample was 50-60%, expanding rate was the optimum condition and the rate was 67-76%. As the thickness of the sample layers was increased, drying-rate was decreased conversely and this result seemed to be due to decline of heat and mass transfer coefficients. Differences with the position of its stalk were also observed in drying rate, and low stalk position leaves of 5 and 3 was the fastest. Key words : freeze drying, Popping, expansion tobacco.

• 한국식품영양학회지
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• 제13권2호
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• pp.152-157
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• 2000

In order to select the optimum drying method for the production of cinnamon extract, water extract and 70% ethanol extract of cinnamon were prepared. And then several drying method of oven drying, vacuum evaporation, spray drying and freeze drying were performed. Content of cinnamic acid, cinnamic aldehyde, eugenol, tannin and free sugar, and antioxidant activity, degree of browning, pH, color value, turbity and solubility were compared. In water extract, contents of cinnamic acid, cinnamic aldehyde, eugenol were 29.45mg/100g, 94.86mg/100g, 120.75mg/100g and decreased to 4.76%∼44.21%, 5.30%∼48.05%, 3.66%∼21.83% by oven dyring, vaccum drying, spray drying respectively, but freeze drying showed a little decrease of those components. In 70% ethanol extract, effectual components decreased to 76.05%∼88.38% and 26.86%∼78.76% by freeze drying and vacuum evaporation respectively. Antioxidant activity decreased by drying and decreasing rate in 70% ethanol extract was lower than water extract. Degree of browning increased as the drying temperature increased. Tannin and free sugars were little affected by drying temperature. Solubility decreased in oven drying and 70% ethanol extract. Overall data suggested that optimum drying methods of cinnamon extract were freeze drying in case of water extract and freeze drying and vaccum drying in case of 70% ethanol extract.

• 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.

• 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.

• 약학회지
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• 제43권6호
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• pp.793-797
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• 1999

Salmonella typhi Ty21a is an attenuated strain of S. typhimurium and used for oral typhoid vaccine. In an attempt to increase the stability of Ty21a manufacturing typhoid vaccine, we studied about the stability of freeze-dried Th21a including additives at various temperature conditions. In order to investigate the freeze-drying rate of Ty21a according to various absorbance, we lyophilized Ty21a by using 8% sucrose as a stabilizer. The optimal freeze-drying rate of Ty21a was appeared when OD (optical density) value of the growth was between 2.5 and 3.0. To investigate the stability of Ty21a at various temperature, the viability was measured after storaging the freeze-dried Ty21a at the room temperature, cold and freezing condition for 1 week. The viability of Ty21a in cold and freezing storage condition was 5 times more stable than in room temperature. To search the most stable additives for the freeze-dried Ty21a, the viability of Ty21a including additives at the various storage condition was estimated. Mannitol and loctose were the most stable additives. Theses results suggest that the OD value of Ty21a growth, low temperature, mannitol and lactose are important factors for the optimal freeze-drying rate, the stable storage and the most stable additives, respectively.

• 한국식품과학회지
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• 제21권1호
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• pp.145-148
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• 1989

건조표고버섯의 품질을 향상시키기 위해 열풍, 원적외선 및 냉동 건조시 건조조건이 품질에 미치는 영향에 대해 조사하였다. $45-70^{\circ}C$ 범위에서 열풍건조시 온도가 증가할수록 부피유지율은 높았으나 복수율은 낮았으며 5'-GMP 함량은 $50^{\circ}C$에서 건조한 것이 가장 많았다. 원적외선 전조는 같은 온도에서의 열풍건조에 비해 복수율은 높았으나 부피유지율이 낮았다. 냉동건조시 냉동속도에 따른 부피유지율의 차이는 뚜렷하지 않았지만 복수율은 $-18^{\circ}C$에서 냉동시킨 것이 가장 높았으며 건조속도에 의한 영향은 건조속도가 빠를수록 복수율이 증가하였다. 또한 냉동속도와 건조속도가 빠를수록 5'-AMP, 5'-GMP 와 5'-XMP 함량이 모두 증가하는 경향이었다.

• Journal of Biosystems Engineering
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• 제13권4호
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• pp.38-45
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• 1988

마늘즙의 동결건조(凍結乾燥)에 영향(影響)을 주는 주요(主要) 인자(因子)는 건조실(乾燥室)의 압력(壓力), 선반(船盤)의 온도, 시료(試料)의 두께, 시료(試料)의 농도(濃度)에 관한 영향(影響)을 시험(試驗) 분석(分析)한 결과(結果) 다음과 같은 결론(結論)을 얻었다. 가, 건조실(乾燥室)의 압력증가(壓力增加)는 건조속도(乾燥速度)를 증가(增加)시키며, 0/6Torr 부근(附近)에서 최대건조속도(最大乾燥速度)에 이르며 이보다 큰 압력하(壓力下)에서는 건조속도(乾燥速度)가 급격(急擊)하게 감소(減少) 하였으며 1.5Torr에서는 발포현상(發泡現象)을 일으키는 동결건조(凍結乾燥)는 부적합(不適合)하였다. 나. 동결온도를 높일수록 건조속도(乾燥速度)가 커지므로 선반온도를 올리는 것이 동결건조(凍結乾燥)에 유리(有利)하나 $10^{\circ}C$이상(以上)은 적절(適切)하지 않으며 선반온도를 $20^{\circ}C$로 올리면 시료(試料)가 발포(發泡)와 비산현상(飛散現象)을 일으키므로 건조(乾燥)가 불가능(不可能)하였다. 다. 고형물(固形物)을 함량(含量)이 증가할수록 건조속도(乾燥速度)는 늦어지는 경향(傾向)을 알 수 있었으나 평형수분함량(平衡水分含量)에 도달(到達)되는 시간(時間)을 기준(基準)으로 한 경제성(經濟性)을 고려(考慮)할 때 약(約) 30%의 원래(原來) 농도(濃度)가 가장 유리(有利)하다고 판단(判斷)되어진다. 라. 시료(試料) 두께가 커질수록 건조속도(乾燥速度)가 작아지며 시료(試料) 높이가 약 3.0cm에서 발포현상(發泡現象)이 관찰(觀察)되었다. 건조(乾燥)에 소요(所要)되는 시간(時間) 등(等)으로 판단(判斷)할 때 시료(試料) 높이가 약(約) 1.0cm가 가장 적절(適切)한 것으로 판단(判斷)되었다.