• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1337-1344
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• 1999

Lactic acid bacteria fermented foods were prepared from egg white powder, casein and growth stimulating agent. pH change and growth of Lactbacillus acidophilus(KCTC 2182) during freeze drying were studied. The effects of freeze drying on sensory evaluation. hardness and volatile aroma compounds in freeze dried sample or reconstituted sample were also studied. Freezing and freeze drying did not affect pH of fermented samples. Number of viable cells in original fermented samples was markedly reduced during freezing or freeze drying. When number of viable cells in original fermented sampler was considered at 100%. survival ratio of viable cells after freezing was $72.0{\sim}82.4%$ and that after freeze dying $10.0{\sim}20.4%$. When sensory properties of original fermented samples were compared with those of freeze dried/reconstituted samples, sensory properties of original samples were generally better than those of freeze dried/reconstitute samples. However, the reconstitution property and the acceptability of freeze dried samples were good. Volatile aroma compounds in original fermented samples were reduced during freeze drying. The reduction degree of volatile aroma compounds varied with sample.

• Journal of Life Science
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• v.10 no.3
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• pp.229-235
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• 2000

The absorption characteristics of Korean yam powder according to different drying methods were investigated. The physical properties of yam powder by different drying methods were showed the biggest porosity in freeze drying sample, while the smallest in hot air drying sample. No difference was founded in proximate compositions of yam powder by various drying methods. The amount of total phenolic compound and Vit C were showed the bigger decrement in freeze dried sample than other drying methods. The time reaching to equilibrium moisture content were determined in 12 days. Monolayer moisture contents were predicted to 0.0508∼0.0588 by BET equation and 0.0705∼0.0811 g H2O/g solid by GAB equation. BET equation for isothermal absorption curve showed over 0.95 R-square for every drying methods. GAB equation showed over 0.99 in vacuum and freeze drying but a poor R-square in hot air drying.

• Food Science and Preservation
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• v.14 no.1
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• pp.61-66
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• 2007

This study investigated changes in physicochemical properties of onion powders during various drying conditions. The moisture content during vacuum drying at $40^{\circ}C$ remained at 5.23% for 5 days of drying, and it was possible to quickly obtain day powder Weight reduction upon $-70^{\circ}C$ vacuum drying was 90% after 7 days. The large change in browning caused by vacuum freeze drying was lowest ($OD_{420}\;of\;1.173$) after 7 days of drying. The content of vitamin C increased with vacuum freeze drying. The major free sugars were fructose, glucose and sucrose. Of organic acids, citric acid was prominent and, after vacuum freeze drying, showed a high value of 1,965 mg/100g. Free amino acids noted were L-arginine, ${\beta}-alanine$, L-alanine and L-threonine. In summary, vacuum freeze drying at $-70^{\circ}C$ is optimal.

• Korean Journal of Food Science and Technology
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• v.40 no.6
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• pp.721-725
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• 2008

Changes in the physicochemical and sensory characteristics of the uncooked food, Codonopsis lanceolata saengsik, were investigated to determine an efficient drying method, one of the most important manufacturing processes in the preparation of C. lanceolata saengsik. No changes in the proximate compositions of all samples were observed during hot-air drying at 50 and $60^{\circ}C$ and freeze-drying. The L value in the freeze-dried sample was higher than that in the hot-air dried samples, whereas the b value in the freeze-dried sample was reduced. Dietary fiber content in the hotair dried samples were higher than that in the freeze-dried sample, whereas the total phenolic compounds and crude saponin contents were lower than those in the freeze-dried sample. The highest overall acceptability values in the sensory test for color, flavor, taste, and overall acceptability were 5.63, 5.45, 5.75, and 5.85, respectively. In conclusion, the freezedrying method was the most favorable of the tested method for the manufacture of C. lanceolata saengsik.

• 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.44 no.6
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• pp.716-721
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• 2012

This study was designed to compare the quality characteristics of spray-dried (SD) and freeze-dried (FD) powders prepared with hot water extracts of sea mustard (Undraia pinnatifada) and sea tangle (Laminaria longissima). The moisture content of FD seawed was lower than that of SD, and sea mustard had a higher overall moisture content than sea tangle. The alginic acid content of SD seaweed was significantly higher than that of FD seaweed for both species. There were relatively higher contents of phenolic compounds in SD powders than in FD powders. DPPH radical scavenging ability was significantly greater in SD seaweed, and also, SOD-like activity in SD powders was higher than those of FD powders. However, the nitrite scavenging activity of FD powders of sea mustard (10 mg/mL) was higher than that of SD. In conclusion, spray-dried sea mustard and sea tangle extracts exhibited higher physiological functionalities than their freeze-dried counterparts.

• Korean Journal of Food Science and Technology
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• v.38 no.4
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• pp.506-512
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• 2006

We investigated changes in the physicochemical characteristics and functional components of the Saengsik cereal grains-milled rice, brown rice, glutinous rice, and barley- by washing with electrolyzed water. There were no changes in the composition of all cereal grains that was dried with hot-air and freeze-dried after being washed with electrolyzed water. The L and a values were not affected by drying in milled rice, brown rice, glutinous rice, or barley, but the b value increased in milled rice and glutinous rice-this increase was greater with hot-air drying than with freeze-drying. The dietary fiber content of the all cereals increased with hot-air drying. The niacin content decreased in all cereals; the extent of this change was greater with hot-air drying than with freeze-drying. The ${\beta}-glucan$ content of barley was higher in samples that underwent freeze-drying than in those treated by hot-air drying, but was not affected by washing with electrolyzed water. Thus, other than a change in color for milled and glutinous rice, no changes in the physicochemical characteristics and functional components these products were observed with freeze-drying. Data indicate that the electrolyzed water washing could be effectively used as pasteurization step in the uncooked cereal grains.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.555-564
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• 1990

The headspace gas chromatographic(analytical) technique was used to evaluate the retention of volatiles in fruit juices during freeze drying as a function of freezing rate, the content of initial solid and chamber pressure. The effects of freezing rate and drying time on the volatile retention under the experimental conditions were marked, particulary at long freezing time. The retention of volatiles in the freeze dried was largely affected by the freezing rate. The highest volatile loss under the freeze drying conditions was observed during the first stage of drying. The behavior during freeze drying of the volatile substances was affected by high content of initial solid. The volatile retention was higher in quick freeze drying than slow freeze drying and low pressure than high.

• Korean Journal of Food Science and Technology
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• v.34 no.5
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• pp.805-810
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• 2002

Development of tenderizer using domestic fruits was studied. Kiwifruit was dried using various methods, and the quality of kiwifruit powder was observed during 12 week storage. Frozen kiwifruit was prepared in paste, dice, and whole flesh. After drying, paste-type kiwifruit showed 2.0 and 1.3 times higher proteolytic activity than dice and whole flesh kiwifruits, respectively. Nine hour of hot-air drying or 46 h of freeze-drying eliminated more than 90% of water from kiwifruit, during which discoloring of kiwifruit occurred. Freeze-dried powder showed 6.6 times higher yield and proteolytic activity, and resulted in almost no discolorization than those of air-dried powder. Addition of bulking agent affected the quality of hot air-dried kiwifruit powder, except color, resulting in $3.2{\sim}3.6$ times higher proteolytic activity than that without bulking agent, which is comparable to 60% of the initial freeze-dried powder content. Moisture content of kiwifruit powder with bulking agent sustained consistently during 12 week storage, whereas proteolytic activity decreased for the first 4 weeks. Freeze-drying is a preferable method to produce kiwifruit powder for tenderizer, although hot air-drying with bulking agent treatment is more economical.

• Food Science and Preservation
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• v.23 no.6
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• pp.819-824
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• 2016

The changes in physicochemical characteristics and sensory evaluation of bracken (Pteridium aquilinum) and Aster scaber dried by different methods sun-dried, hot-air-dried and freeze-dried were investigated. The freeze-dried Aster scaber showed the lowest moisture content than those of sun-dried and hot-air-dried. Freeze-dried bracken and Aster scaber showed higher rehydration rate than sun-dried and hot-air-dried. In the color values, the freeze-dried bracken and Aster scaber had the highest $L^*$ value of 29.48 and 32.73, respectively, while freeze-dried Aster scaber showed the lowest $a^*$ value of -6.78. Rehydrated bracken and Aster scaber after freeze-dried were the highest value in $L^*$ and $b^*$, while the lowest in $a^*$ value. In sensory evaluation, freeze-dried bracken and Aster scaber showed the highest in color, appearance, flavor, texture and overall acceptability. There were no significant differences in texture between hot-air-dried bracken and freeze-dried bracken after rehydrating. However, freeze-dried bracken and Aster scaber were the highest in color, appearance, flavor and overall acceptability. In conclusion, freeze-dried bracken and Aster scaber showed the best rehydrated rate, color and sensory properties.