• Applied Microscopy
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• v.28 no.3
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• pp.299-306
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• 1998

T-butyl alcohol (TBA) freeze-drying method originally designed by Inoue and Osadake (1989) was adopted to dry specimens for scanning electron microscopy and the results were compared with those dried using critical point dryer (CPD). Small pieces $(1\times1\times3mm)$ of liver of Sprague-Dawley rats were cut and fixed in 2% glutaraldehyde in 0.1 M sodium cacodylate buffer after anesthesia, and processed for scanning electron microscopy by several modifications of TBA freeze-drying methods and by the standard preparation method using CPD. The bile canaliculi and sinusoidal endothelial surface were observed. Tissue dehydrated with TBA before TBA freeze-drying preserved the structures best comparable to those prepared with CPD. This result suggests that combination of dehydration with TBA and TBA freeze-drying is a superior method to the original TBA freeze-drying method dehydrated with ethanol.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1341-1352
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• 2001

Vacuum freeze drying process by which frozen water in a drying material is removed sublimation under vacuum condition, is now applied to various industrial field such as the manufacturing and packaging of pharmaceuticals in pharmaceutical industry, the drying of bio- products in bio-technology industry, the treatment of various quality food stuff in food technology, and so on. The Knowledge about the heat and mass transfer characteristics related with the vacuum freeze drying process is crucial to improve the efficiency of the process as well as the quality of dried products. In spite of increasing needs for understanding of the process, the research efforts in this fields are still insufficient. In this paper, a numerical code that can predict primary drying in a vial is developed based on the finite volume method with a moving grid system. The calculation program can handle the axis- symmetric and multi-dimensional characteristics of heat and mass transfer of the vial freeze drying process. To demonstrated the usefulness of the present analysis, a practical freeze drying of skim Milk solution in a vial is simulated and various calculation results are presented.

• Archives of Pharmacal Research
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• v.29 no.9
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• pp.735-740
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• 2006

Lactic acid bacteria (LAB) quickly attenuate or are killed during the freeze-drying process and storage. The effect of some natural polysaccharides, which are known as potent antitumor and immunomodulating substances, on the viability of the LAB, Lactobacillus acidophilus and Bifidobacterium breve, on freeze-drying and storage were investigated. Among the polysaccharides tested, red ginseng polysaccharide (RGP) and chitosan significantly inhibited the cell death of the LAB during freeze-drying, and fucoidan and RGP most potently protected the cell death of the LAB during storage. The stabilities of the LAB on the addition of RGP and fucoidan were comparable to that of skimmed milk. However, white ginseng polysaccharide (WGP) did not promote storage stability. When 5% skimmed milk/5% RGP treated LAB were freeze-dried and stored, their viabilities were found to be significantly higher those treated with 5% or 10% RGP. The stabilizing effect of 5% RGP/5% skimmed milk during LAB freeze-drying and storage stability was comparable to that of treatment with 10% skimmed milk. Based on these findings, we believe that RGP beneficially improves the stability of LAB during the freeze-dry process and storage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.5
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• pp.1058-1063
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• 1999

The purpose of this study was to investigate the differences in proximate composition, free sugars, organic acids, fatty acids, amino acids, mineral components, hunter color values and calory values between freeze dried and steam dried Gastrodia elata Blume. Crude fat and crude fiber decreased during manu facture of steam dried Gastrodia elata Blume. The contents of sugars in steam dried Gastrodia elata Blume decreased during manufacture than that of freeze dried Gastrodia elata Blume. The contents of malic acid, oxalic acid, ketoglutaric acid, malonic acid and succinic acid in freeze dried were similar to those in steam dried Gastrodia elata Blume. Citric acid decreased in steam dried Gastrodia elata Blume. The contents of linoleic acid, palmitic acid and oleic acid in freeze dried were similar to those in steam dried Gastrodia elata Blume. The contents of free amino acids in steam dried Gastrodia elata Blume decreased during manufacture. The mineral component contents of the Gastrodia elata Blume were greater in the order of Mn

• Preventive Nutrition and Food Science
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• v.20 no.2
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• pp.143-147
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• 2015

Systematic study of how different drying methods, namely hot-air drying, vacuum-drying, and freeze-drying, affect color, browning index, degree of rehydration, water solubility, and vitamin C content is critical for utilizing pine needle powders (PNP) as a novel ingredient in functional foods. Samples prepared by vacuum-drying showed a significantly higher $L^*$-value, whereas higher $a^*$- and $b^*$-values were detected in the hot-air dried samples (P<0.05). The browning index was significantly higher in samples prepared by vacuum-drying compared to samples prepared by freeze-drying (P<0.05). Freeze-dried PNP exhibited a significantly higher degree of rehydration than hot-air dried samples (P<0.05). Water solubilities of freeze-dried and hot-air dried samples were significantly higher than that of vacuum-dried sample (P<0.05). Vitamin C was less destroyed during freeze-drying compared to hot-air or vacuum-drying (P<0.05). Freeze-dried samples displayed a clear porous structure and appeared to have a bigger space, whereas hot-air dried samples showed lower porosity than vacuum and freeze-dried samples.

• 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.

• Journal of information and communication convergence engineering
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• v.13 no.1
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• pp.21-26
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• 2015

A wireless sensor network (WSN) is designed and implemented for a freeze dryer. Freeze-drying technology is widely used in the fields of pharmacy and biotechnology as well as the food and agriculture industries. Taking into account the demand for high-resolution pressure and temperature measurements in a freeze dryer, the proposed WSN has a significant advantage of creating a monitoring environment in a freeze dryer. The proposed WSN uses a ZigBee/IEEE 802.15.4 network with an altimeter module that contains a high-resolution pressure and temperature sensor with a serial digital data interface. The ZigBee network is suitable for low-energy and low-data-rate applications in the field of wireless communication. The altimeter module is capable of sensing pressure in the range of 7.5-975 Torr (10-1300 mbar) and temperature in the range of $-40^{\circ}C$ to $125^{\circ}C$ with a DC power consumption of $3{\mu}W$. The implemented WSN is installed in a commercial laboratory freeze dryer in order to demonstrate its functionality and efficiency. A comparison with the temperature profile measured by a thermocouple installed in the freeze dryer reveals that the resolution of the temperature profile measured by WSN is superior to that measured by the thermocouple.

• Journal of Microbiology and Biotechnology
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• v.32 no.12
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• pp.1599-1604
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• 2022

Storage stability of freeze-dried lactic acid bacteria is a critical factor for their cost-effectiveness. Long-term storage of lactic acid bacteria enables microbial industry to reduce distribution costs. Herein, we investigated the effect of cold adaptation under supercooling conditions at -5℃ on the viability of Leuconostoc mesenteroides WiKim32 during the freeze-drying process and subsequent storage. Cold adaptation increased the thickness of exopolysaccharides (EPS) and improved the viability of freeze-dried Leu. mesenteroides WiKim32. Compared to non-adapted cells, cold-adapted cells showed a 35.4% increase in EPS thickness under supercooling conditions. The viability of EPS-hydrolyzed cells was lower than that of untreated cells, implying that EPS plays a role in protection during the freeze-drying process. Cold adaptation increased the storage stability of freeze-dried Leu. mesenteroides WiKim32. Fifty-six days after storage, the highest viability (71.3%) was achieved with cold adaptation at -5℃. When EPS-containing broth was added prior to the freeze-drying process, the viability further increased to 82.7%. These results imply that cold adaptation by supercooling pretreatment would be a good strategy for the long-term storage of Leu. mesenteroides WiKim32.

• Journal of Dairy Science and Biotechnology
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• v.33 no.3
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• pp.203-207
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• 2015

The majority of food drying processes are based on the use of thermal energy. However, such methods may deteriorate the quality of the final product. Freeze-drying is one of the most useful processes for drying thermosensitive substances. Food that contains beneficial bacteria, for example, is susceptible to heat treatment, but during freeze-drying beneficial bacteria are preserved in these food items. The primary goals of this study were to develop yogurt snacks and to compare the viability of lactic acid bacteria (LAB) in yogurt snacks under different freeze-drying temperatures. In addition, the survival of LAB during storage was investigated. Survival of LAB in freeze-dried yogurt snacks gradually decreased over 16 weeks of storage. LAB had a residual viability of 25.5% after 16 weeks of storage at room temperature. LAB survived better in freeze-dried plain yogurt snacks than in freeze-dried strawberry yogurt snacks during storage. Freeze-dried yogurt snacks contained 11.9% fat, 57.1% carbohydrate, and 18.7% protein. In conclusion, the viability of LAB in freeze-dried yogurt snacks depends on the temperature during freeze-drying: the higher the freeze-drying temperature, the lower the viability of LAB in yogurt snacks. The viability of LAB in yogurt snacks was also dependent on the moisture content and nutritional value.

• 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.