• 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.

• Microbiology and Biotechnology Letters
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• v.8 no.1
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• pp.19-25
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• 1980

Trials of investigating the effect of freezing and lyophilization, as the practical lactic starter preservation methods, on the viability and lactic acid producing activity of Lactobacillus bulgaricus NLS-4 have been carried out. After the treatments, both of viability and activity were decreased. However, when the initial cell cocentration was increared, the survival rate against freezing could be raised to 46% and the activity to 0.25% lactic acid whereas those against lyophilization were 22 ％ and 0.29% lactic acid, respectively. There were further increased maximally when the cell suspension was subjected to freezing and lyophilization after the addition of protective agents such as glycerol and the G. C. G. S. suspending medium.

• Food Science and Preservation
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• v.21 no.3
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• pp.341-349
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• 2014

The antioxidative effect and quality characteristics of different drying methods (hot air drying, far-infrared radiation drying, vacuum freeze drying) from Schizandra Chinensis Baillon were investigated. The moisture contents and water activity(Aw) contents each 4.46% and 0.38 values of the vacuum freeze drying were lower than those of other samples. A significant not difference in pH values occurred in all samples (p<0.05). The highest content $^{\circ}brix$ vacuum freeze drying was $6.60^{\circ}Brix$ respectively. The turbidity values of the samples were hot air drying 8.24 T%, far infrared radiation drying 0.32 T%, vacuum freeze drying 71.85 T%. The Hunter's L, a and b values of vacuum freeze drying were higher than those of other samples. The order of the free sugar content was glucose>fructose>sucrose, and that of the total free sugar contents were vacuum freeze drying (6.33 g/100 g) > far infrared drying (5.01 g/100 g) > hot air drying (3.73 g/100g). Antioxidant acitivy (DPPH radical scavenging, ABTS radical scavenging) and total phenol, total flavonoid, and total tannin content was highest in vaccum freeze drying than other different drying methods except nitrite scavenging ability.

• Food Science and Preservation
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• v.7 no.4
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• pp.389-394
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• 2000

To utilize deteriorated sweet persimmon(Diospyros kaki T.) effectively, this study was investigated about the effective (Dying method of the powder. Chemical components, minerals, fatty acids and amino acids of hot-air dried and freeze dried conditions were determined Sample conditions used on analysis as follow; pretreatments of hot-air dry and freeze dry were soft, soft+peel, mixer, mixer+peel. The contents of crude protein, crude lipid, crude ash of hot-air dry were 0.9-1.1%,15.0-39.0% and 2.3-3.3%, respectively. And those of freeze dry were 1.3-2.2%, 27.-49.0% and 2.5%, respectively. Potassium, magnesium, phosphorus, calcium and sodium content in hot-air dry and freeze dry were high. Other minerals were less than 3.00ppm in all conditions. The major fatty acid contents were detected capric acid(C$\^$10:0/), lauric acid(C$\_$l2:0)/, tridecanoic acid(C$\_$13:00/), palmitic acid(C$\_$l6:00/), palmitoleic acid(C$\_$l6:1/), oleic acid(C$\_$18:1), linoleic acid(C$\_$18:2/), linolenic acid(C$\_$18:3/). The essential amino acids such as aspartic acid, threonine, serine, glutamic acid, glycine, alanine, valine, methirmine, isoleucine, leucine, tryosine, phenylalanine, histidine, lysine, arginine in freeze dry were contained richly. On the basis of chemical analysis, hot-air dry method will have to supply the additional different method, because simple hot-air dry method was shorten the dry time but had many problems. Therefore, the effective drying method considering changed color and nutrition was shown freeze dry method.

• Food Science and Preservation
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• v.22 no.1
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• pp.56-62
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• 2015

In this study, the quality characteristics of different drying methods of Aronia melanocarpa, which contains large amounts of bioactive substances, were investigated for the improvement of their practical use. During the drying period, the weight reduction was the highest with vacuum freeze drying (81.6%). The water content was reduced to the maximum level when vacuum freeze-drying was used. With regard to the color value measurement results, there were no significant differences in the $L^*$ value. Values of $a^*$ and $b^*$ were increased in vacuum freeze drying and cold air drying, but decreased in hot air drying. The hardness was increased dramatically after 36 hours of hot air drying, while with cold air drying, it increased slowly until 132 hr and increased rapidly after 132 hr. The dried yield was the highest with cold air drying (24.2%). As for the general component analysis results of Aronia melanocarpa, the moisture content was the lowest, and the crude protein and crude fat contents were the highest with vacuum freeze drying. No difference in pH value was shown among the dried Aronia melanocarpa obtained from the different drying methods, but the sugar content was the highest with vacuum freeze drying. The mineral content was the highest with cold air drying, and K, Ca, Mg, and Na were the major minerals. The free sugar content of dried Aronia melanocarpa was found to be 5.92~20.59 g/100 g, and the highest free sugar content was found with vaccum freeze drying.

• 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.

• 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.12 no.5
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• pp.436-441
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• 2005

This study was observed the effects of drying methods on the extraction characteristics of Rubi fructus (fruits of Rubus coreanus). Extraction yields of soluble solids and total sugar were high in the Rubi fructus dried by freeze drying, followed by infrared drying and sun drying. Extraction yield of phenolic compounds and DPPH radical-scavenging activity of extracts were in the following order; the Rubi fructus dried by freeze drying, the Rubi fructus dried by infrared drying, the Rubi fructus dried by sun drying. L value was the highest in the Rubi fructus dried by freeze drying, and a and b value were lowest in the fruit dried by freeze drying. These results suggest that freeze drying has an beneficial effect to enhance the quality of Rubi fructus. Water and ethanol extractions was more effective in the extraction of soluble solids and the antioxidative components.

• 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.

• 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.