• Journal of Biosystems Engineering
• /
• v.34 no.3
• /
• pp.155-160
• /
• 2009

This study was attempted to quality characteristics of ginseng powder using molecular press dehydration(MD) method. Ginseng powder was dried using maltodextrin as dehydrating agents, and the quality of the ginseng powder was compared with that of freeze-drying and hot air-drying samples in terms of colors, moisture contents and grain size. The colors of ginseng powder using MD-drying and freeze-drying was better than hot air-dried ginseng powder. The moisture contents of ginseng powder using MD-drying was 9.49%, while freeze-drying was 4.14% and hot air-drying 11.71% after 72ball mill times. The grain size of ginseng powder using MD-drying and freeze-drying was better than hot air-drying ginseng powder. These results suggest that drying of ginseng powder using molecular press dehydration method is very efficient, because minimal cell destruction may be achieved.

• Journal of Power System Engineering
• /
• v.15 no.3
• /
• pp.46-51
• /
• 2011

Low temperature vacuum drying technique, whose drying time and quantity of exhausting energy is about 25~30% of hot air drying, is very excellent in the drying efficiency. This paper is made out in the aspects of heat engineering with the object of developing Korean drying machine which can dry once a large quantity of objects to be dried in the state of low temperature and vacuum. As the results, it took about 17 hours(3~4 days in case of hot air drying) for material to reach about 18% of the final moisture content in order to store products for a long time, from about 78~80% of the early moisture content at the beginning of drying, and maximum drying rate comes to about 0.35 kg/m2hr at about 400% of the moisture content.

• Journal of Ginseng Research
• /
• v.9 no.2
• /
• pp.248-255
• /
• 1985

In order to investigate the optimal drying condition of white ginseng by using bulk air drier(130 x 62 x 65cm), drying curves, diffusion coefficient at various drying temperature, the energy of activation, variation of color intensity and chemical components during drying of white ginseng were studied. Fick's second low of diffusion for diffusion out of spheres was successfully applied to describe the drying of white ginseng. It was found that the diffusion coefficient of water was 2.2x107, 9.0x107 cm2/sec at drying temperature 4$0^{\circ}C$, 55$^{\circ}C$, respectively. An Arrhenius type temperature dependency of moisture diffusivity was found, the energy of activation being 18.8 Kcal/g mol. Color intensity of white ginseng dried at various drying temperature was increased with an increase in drying temperature. The contents of crude protein, reducing sugar and crude saponin during drying of white ginseng were gradually decreased as increasing of drying time. And with the sensory evaluation by multiple comparison difference analysis, the optimal drying temperature of white ginseng was between 45$^{\circ}C$ and 5$0^{\circ}C$.

• Journal of Biosystems Engineering
• /
• v.41 no.4
• /
• pp.357-364
• /
• 2016

Purpose: This study was performed to define the drying characteristics of sorghum by developing thin layer drying equations and evaluating various grain drying equations. Thin layer drying equations lay the foundation characteristics to establish the thick layer drying equations, which can be adopted to determine the design conditions for an agricultural dryer. Methods: The drying rate of sorghum was measured under three levels of drying temperature ($40^{\circ}C$, $50^{\circ}C$, and $60^{\circ}C$) and relative humidity (30%, 40%, and 50%) to analyze the drying process and investigate the drying conditions. The drying experiment was performed until the weight of sorghum became constant. The experimental constants of four thin layer drying models were determined by developing a non-linear regression model along with the drying experiment results. Result: The half response time (moisture ratio = 0.5) of drying, which is an index of the drying rate, was increased as the drying temperature was high and relative humidity was low. When the drying temperature was $40^{\circ}C$ at a relative humidity (RH) of 50%, the maximum half response time of drying was 2.8 h. Contrastingly, the maximum half response time of drying was 1.2 h when the drying temperature was $60^{\circ}C$ at 30% RH. The coefficient of determination for the Lewis model, simplified diffusion model, Page model, and Thompson model was respectively 0.9976, 0.9977, 0.9340, and 0.9783. The Lewis model and the simplified diffusion model satisfied the drying conditions by showing the average coefficient of determination of the experimental constants and predicted values of the model as 0.9976 and Root Mean Square Error (RMSE) of 0.0236. Conclusion: The simplified diffusion model was the most suitable for every drying condition of drying temperature and relative humidity, and the model for the thin layer drying is expected to be useful to develop the thick layer drying model.

• Journal of the Korean Wood Science and Technology
• /
• v.10 no.3
• /
• pp.167-167
• /
• 1982

Italian poplar (Populus euramericana) rotary veneers were press-dried and air-dried to study drying curves, thickness shrinkage and width shrinkage of them under several drying conditions such as drying temperatures and veneer thicknesses. The results of the study are summarized as follows; 1. In press-drying, drying times from green condition to about final moisture content of 10 percent with veneer thickness of 0.6mm by platen temperatures required about 10 minutes at platen temperature of $100^{\circ}C$, 3 minutes at $110^{\circ}C$, 1 minute at $120^{\circ}C$ and $130^{\circ}C$, respectively. 2. In press, drying, drying times from green condition to about final moisture content of 10 percent by veneer thicknesses required 2 minutes at veneer thickness of 0.6mm, 4 minutes at 1.2mm,6 minutes at 1.8mm and 9 minutes at 3.6mm, respectively. 3. In air-drying, drying times from green condition to air-dried moisture content by veneer thicknesses required 15 hours at veneer thickness of 0.6mm, 18 hours at 1.2mm and 23 hours at 2.4mm, respectively. 4. Thickness shrinkage of press-drying was remarkably greater than that of air-drying, but width shrinkage of press-drying was rather smaller. 5. Difference of thickness shrinkage among platen temperatures was insignificant, and width shrinkage at platen temperature of $130^{\circ}C$ was the least.

• Journal of Biosystems Engineering
• /
• v.22 no.3
• /
• pp.279-288
• /
• 1997

This study was worked out to obtain fundamental data needed for developing a continuous type dryer. The drying process in a cross-flow type continuous dryer was expressed as partial differential equations, and a drying simulation model for predicting rice moisture content, rice temperature, drying air absolute humidity, drying air temperature was developed by using the finite difference method. To validate the performance of the drying simulation model, a prototype continuous dryer was constructed in this study. The size of the test dryer was one-tenth to that of a commercial continuous dryer. The difference in the outlet rice moisture content between the predicted values and the measured values was within 0.5%, that of outlet rice temperature was below $3^{\circ}C$, that of drying air temperature in drying bed was within $8^{\circ}C$ and that of relative humidity of outlet drying air was big because of the different measuring point. In addition, a drying simulation model for a actual size continuous dryer with double flow was developed in this study. This drying simulation model included the rice mixing effect in the middle of drying length. The difference of outlet moisture content between the predicted and the measured values showed below 0.5% in this study.

• Journal of environmental and Sanitary engineering
• /
• v.13 no.1
• /
• pp.9-15
• /
• 1998

Microwave heating and drying processes have been well established in various industrial applications. Feasibilities of successful application of microwave drying to many material have been shown on the laboratory or pilot-plant scale. The microwave drying behavior of plating sludge are considered in this paper. The plating sludge containing 70%, 80% and 90% water exposed to microwave power at 2,450 MHz, 700W. An experimental microwave drying apparatus was designed and constructed to monitor weight loss during drying. By studying the drying characteristic curve, the moisture in sludge was almost classified into two categories : free moisture and intestinal moisture. And the critical moisture contents at which the drying rate ceases to be constant were from 10.1 to 10.5%. A simple drying model is proposed which may be used to describe drying behavior of plating sludge. The constant rate and the falling rate periods in microwave drying were addressed separately. From the eqation of constant rate period the drying rate constants decreased exponentially with increasing depth. Microwave heating compared with conventional heating offered higher heating rates from 9 to 16 times. Therefore, microwave drying process can be effective in removing moisture from plating sludge.

• Food Science and Preservation
• /
• v.6 no.3
• /
• pp.319-323
• /
• 1999

This study was conducted to minimize the deterioration of dried kiwifruit quality. Osmotic dehydration was carried out as pretreatment before drying. After the kiwifruits were pretreated under optimized osmotic dehydration conditions, they were dried by three drying methods(hot air drying, vacuum drying, freeze drying). Hot air drying and vacuum drying were superior to freeze drying in the drying speed. But vacuum and freeze drying preserved more vitamin C than hot air drying. Also, osmotic dehydrated kiwifruit kept better quality than nontreated kiwifruit. Diffusion coefficient which describes moisture transfer, was high in drying process pretreated with osmosis. The changes of vitamin-C followed the second-order reaction rate equation with high RE, respectively.

• Journal of the Korean Dietetic Association
• /
• v.19 no.4
• /
• pp.389-399
• /
• 2013

This study compared the nutritional composition and antioxidative activity of different parts of Taraxacum coreanum (aerial parts and roots) according to different drying methods (natural drying and freeze-drying). There were no significant differences in vitamin C content in roots depending on the drying methods. However, vitamin A (P<0.01), E (P<0.001) and C (P<0.001) content of aerial parts, and vitamin A (P<0.001) and E (P<0.05) content of roots were significantly higher after freeze-drying compared to natural drying. For organic acids, the oxalic acid content of the aerial parts and roots were the highest. The total polyphenol and total flavonoid content in extracts from the aerial parts (P<0.01) and roots (P<0.05) were significantly higher after freeze-drying compared to natural drying. In addition, the total polyphenol and flavonoid content, DPPH radical scavenging activity, and antioxidative index from the natural drying and freeze-drying of Taraxacum coreanum extracts were significantly higher in the aerial parts compared to the roots (P<0.05). These results suggest that the nutritional composition and antioxidative activity of Taraxacum coreanum are higher in the aerial parts compared to the roots, and higher after freeze-drying compared to natural drying. Therefore, the aerial parts of Taraxacum coreanum could be suggested as an antioxidative functional food source.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2006.06a
• /
• pp.19-29
• /
• 2006

Drying is the least developed of all unit operations of paper and board manufacture. While groundbreaking developments were Introduced during the several past decades in forming, pressing and calendering, no radical changes occurred in drying. The cylinder-drying technology is now more than 200 years old and, while it was subject to many incremental improvements, many of its inherent problems persist. We believe that conventional drying is now approaching the end of its life and the industry is ready for a major breakthrough in drying. Indeed several innovative technologies already exist at various stages of development or commercialization. In general, the novel drying technologies are striving to increase the drying rate, improve the product quality and boost the energy efficiency of drying. A novel, drying method, $Papridry^{TM}$, which combines conductive and convective heat transfer to obtain very high drying rates, is at an advanced stage of development at Paprican. The results obtained when drying printing paper ana board on a self-standing pilot $Papridry^{TM}$ machine and on the pilot paper machine equipped with a tandem of two $Papridry^{TM}$ units demonstrate both, the high drying rate and improved product quality achieved by using this drying method. A mathematical model of this operation has been developed and the software compiled with this model was used to calculate the effect of installing a $Papridry^{TM}$ unit into an existing dryer section. The model also allows to calculate the z-direction distribution of moisture and temperature at various points of the dryer section.