• Korean Journal of Food Science and Technology
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• v.35 no.2
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• pp.329-333
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• 2003

Fruits of 'Manita', a red pepper cultivar, and 'HL', a cultivar bred for single-harvest, cultivated by direct sowing method were harvested simultaneously. The red fruits were freeze-, sun-, indoor-, hot-air $(65^{\circ}C)$, and excessive hot-air (50% longer time) dried. For Manita. ASTA values of freeze- and indoor-dried red pepper were the highest $(153.6{\sim}168.4)$, and those of sun- and hot air-dried ones were $119.2{\sim}131.5$. Excessive hot-air drying decreased the redness by about $9{\sim}15%$ compared to normal hot-air drying. For HL, ASTA values $(150.3{\sim}171.7)$ of indoor-dried red peppers were much higher than other dried peppers. Red pigment in HL was destroyed easily during sun drying, showing values of only $49.2{\sim}69.2$. By excessive hot-air drying, the redness did not decrease, compared to normal hot-air drying. The organic acid contents of both cultivars were higher in sun- and hot-air-dried ones than freeze- and indoor-dried ones. Copsaicinoid contents of both cultivars decreased up to 22% by excessive hot-air drying compared to normal hot-air drying. Sugar contents were lower in all drying methods other than freeze drying for both cultivars.

• Korean Journal of Medicinal Crop Science
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• v.14 no.1
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• pp.8-13
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• 2006

This study was carried out to investigate drying methods for keeping freshness and active components of aerial part of Saururus chinensis. Chopped samples were prepared using hot air drying, hot air drying + roasting, presteamed + hot air drying, freeze drying, and sun drying. Drying time was shorter $88{\sim}93%$ in hot air drying and freeze drying than in sun drying. Percentage of dry matter was higher in the order of freeze drying > sun drying > hot air drying, and moisture content in the order of sun drying > hot air drying > freeze drying. The contents of total phenolics and quercetin related substances were greater in the order of freeze drying > hot air drying > sun drying, while were decreased due to treatments before or after hot air drying. Electron donating ability (EDA) was highest in freeze drying, and showed a little difference between hot air drying and sun drying, but was increased because of treatments before or after hot air drying. In color values, the a value was lower in the order of freeze drying < hot air drying < sun drying. The contents of active components of plant parts of hot air dried were higher in the order of flower >leaf > chopped sample > stem. EDA showed similar tendency with those. The a value was lower in the order of leaf < chopped sample < flower < stem. As a result, freeze drying of chopped samples or hot air drying of leaf and flower were effective to maintain qualities of aerial part of Saururus chinensis.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.226-232
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• 2002

In tradition, there have been two kinds of drying methods, which are sun drying and artificial drying. The sun drying method which has been adopted traditionally has been replaced by the hot-air drying method which is one of the most general methods of artificial drying, with its simple drying system, low initial cost of drying plant, and easy operating method. But the hot-air drying method has some defects ; (1)much energy loss happens due to the discharge of hot air during the drying process, (2)control of drying rate is not easy on account of changing relative humidity of inlet air for uniform hot air temperature, (3)high temperature of floods in drying process brings about the production of low-grade drying products. Also, the hot-air drying method is inducing environmental and sanitary problems which are resulting from the emission of high temperature and high humidity air, including stick on the drying progress. Vacuum drying technique, whose drying time and 7uantity of exhausting energy is about 1/3 ~1/4 of hot air drying, is very excellent in the drying efficiency. As the results, it took about 20 hours for material to reach about 18% of the final moisture content in order to store products for a long time, from about 470% of the early moisture content at the beginning of drying, and maximum drying rate comes to about $0.35 kg/m^2hr$ at about 350% of the moisture content.

• Journal of Ginseng Research
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• v.33 no.4
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• pp.361-366
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• 2009

This research aims to develop a new drying technology using super-heated steam to reduce the time required for drying ginseng and to enhance its quality. The drying rate of ginseng powder treated with hot-air drying after drying with super-heated steam was about 40% faster than the drying rate of ginseng powder treated with hot-air drying. Minimal difference was found between hot-air drying and hot-air drying after drying with super-heated steam in the general composition of the ginseng powder, such as its crude lipid, crude protein, crude fiber, and ash. Moreover, no difference was found between hot-air drying and hot-air drying after drying with super-heated steam in terms of the ginseng powder's mineral and free sugar contents. The crude saponin contents was 5.43% in the ginseng treated with hot-air drying and 5.4% in the ginseng treated with hot-air drying after drying with super-heated steam. The ginseng powder that was treated with hot-air drying after drying with super-heated steam had a slightly higher redness compared to the ginseng powder that was treated with hot-air drying alone. The number of microorganisms of the ginseng powder treated with hotair drying after drying with super-heated steam showed a reduction of one log cycle in the total bacteria and two log cycles in the yeast molds compared to the ginseng powder treated with hot-air drying alone.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.4
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• pp.22-27
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• 2015

Quality characteristics of Shiitake mushroom using two types of dryers, energy-efficient heat pump hot-air dryer and electric heater hot-air dryer were compared. Energy consumed during drying by heat pump hot-air dryer and electric heater hot-air dryer were 22.8 kWh and 28.9 kWh, respectively. Total polyphenol content of heat pump hot-air dryer and electric heater hot-air dryer after drying were $290.55{\pm}10.56ppm$ and $192.99{\pm}6.53ppm$, respectively. No differences were observed between dryers in reconstitution rate and browning ratio after drying. Also, there were no differences between dryers in color value and ${\Delta}E$ value after drying. Shiitake mushroom drying at $45^{\circ}C$ by heat pump hot-air dryer was proved to be more efficient in energy consumption than by electric heater hot-air dryer.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.183-188
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• 2009

RFID method is a non-contact automatic identification technology, which attaches microchips and antennas to an object in a tag form, to send and process information sent to the network using wireless frequency. Drying and curing process is extremely important which minimizes the resistivity of RFID antennas. This research is about the drying characteristic of conductivity ink, and analyzes and compares the hot-air drying process and infrared drying process. Also, the research was done for the improvement in drying performance by using combined process of hot-air and infrared mechanism. The experiment result shows that the hot-air or infrared drying system used alone cannot meet the required performance in drying printing method using conductivity ink. The combined drying system of hot-air and infrared ray showed resistance low enough in short drying and curing time, and this mechanism makes drying and curing process for mass and continuous production possible on-line.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.828-836
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• 2010

The drying is a process that involves coupled and simultaneous heat and mass transfer. When a wet solid is subjected to thermal drying, two processes occur simultaneously. Drying is classified according to heat transfer characteristics in terms of conduction, convection and radiation. In thermal drying, radiation is easier to control than conduction and convection drying and involves a relatively simple structure. In this study, we measured energy consumption, surface hardness of paint and surface gloss with variation of surface temperature of drying materials and drying time. Drying characteristics and energy consumption between heating panels and hot air heating have been presented. The present study shows that a dryer using heating panels is more effective than a hot air dryer from the viewpoint of energy conservation. The hot air dryer, however, was not optimized and more studies on various parameters related to drying will need to be investigated for definite comparison of drying characteristics of the dryers. The result, even if limited, would present the effective availability of paint drying.

• 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 Culture
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• v.38 no.5
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• pp.356-364
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• 2023

This study compared the physicochemical properties of soybean curd residue and black soybean curd residue produced by hot air-drying and freeze-drying. Regardless of drying method, the crude protein, crude ash, crude fiber contents, pH, L, a, b color values and water soluble index were higher in soybean curd residue, whereas total polyphenol contents and antioxidant activity were higher in black soybean curd residue. Significant differences in water absorption index, oil absorption capacity and emulsion activity were observed between soybean curd residue and black soybean curd residue in freeze-drying. On the other hand, the emulsion stability was not significant difference in both hot-air drying and freeze-drying. The crude protein and crude fiber contents of soybean curd residue were not significant difference between hot-air drying and freeze-drying. Freeze-drying resulted in higher crude ash contents, pH, water absorption index, water soluble index, oil absorption capacity, emulsion activity and emulsion stability than hot-air drying. Hot-air drying have caused significantly higher water contents, water activity, total polyphenol contents and antioxidant activity in soybean curd residue than freeze-drying. In conclusion, soybean type and drying methods affect the physicochemical and quality characteristics of soybean curd residue, which could be important factors in the manufacture of processed foods.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.51-60
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• 1997

We investigated the characteristics of air-and vacuum-drying heated by hot plates for 8~14cm-diameter logs or 6~12cm-thick pillars of Pinus koraiensis. And we evaluated the effects of longitudinal kerf and vacuum drying heated by hot plates. The vacuum drying times from green to 10.9~18.6% MC were 15 days, and these times were one-fifth compared to the air-drying times. The longitudinal kerfing had no significant, effect on drying rates during both air-drying and vacuum drying. But drying defects such as surface checks and V-shaped cracks were effectively prevented during air-drying and vacuum drying by longitudinal kerfing. The vacuum drying was more advantageous than air-drying for preventing of surface checks, end checks and V-shaped cracks, and especially, the vacuum dried pillars with longitudinal kerf were almost free from drying defects. In accelerated weathering conditions the resin did not exude for all specimens.