• 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 Powder Materials
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• v.26 no.3
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• pp.225-230
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• 2019

To develop Taraxacum platycarpum extract (TP)-loaded particles for tablet dosage form, various TP-loaded particles composed of TP, dextrin, microcrystalline cellulose (MCC), silicon dioxide, ethanol, and water are prepared using a spray-drying method and fluid-bed-drying method. Their physical properties are evaluated using angle of repose, Hausner ratio, Carr's index, hardness, disintegrant time, and scanning electron microscopy. Optimal TP-loaded particles improve flowability and compressibility. Furthermore, 2% silicon dioxide gives increased flowability and compressibility. The formula of TP-loaded fluid-bed-drying particles at a TP/MCC/silicon-dioxide amount of 5/5/0.2 improves the angle of repose, Hausner ratio, Carr's index, hardness, and disintegrant time as compared with the TP-loaded spray-drying particles. The TP-loaded fluid-bed-drying particles considerably improve flowability and compressibility ($35.10^{\circ}$ vs. $40.3^{\circ}$, 0.97 vs. 1.17, and 18.97% vs. 28.97% for the angle of repose, Hausner ratio, and Carr's index, respectively), hardness (11.34 vs. 4.7 KP), and disintegrant time (7.4 vs. 10.4 min) as compared with the TP-loaded spray-drying particles. Thus, the results suggest that these fluid-bed-drying particles with MCC and silicon dioxide can be used as powerful particles to improve the flowability and compressibility of the TP.

• Journal of the Korean Wood Science and Technology
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• v.46 no.4
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• pp.301-308
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• 2018

This study aimed to obtain basic climate information for effective moisture control in wood in Korea. Two independent climate indexes, namely drying index (DI) and wetting index (WI), were determined using hourly weather data for 82 locations recorded from 2009 to 2017. These data were collected from the Korea Meteorological Administration (KMA). Hourly data had not been measured prior to 2009. DI and WI revealed that all regions were cold and wet except Baengnyeongdo, which was classified as a cold and dry region. DI and WI were normalized assuming that wetting and drying were equally important phenomena. Then, the normalized indexes were combined into moisture index (MI) to rank the moisture loading of the regions. The MIs showed that Seogwipo had the greatest moisture loading in Korea, followed by Seongsan, Namhae, and Geoje. The MIs suggested that Korea exhibited severe moisture loading. Further studies are required to investigate the relation between MI and moisture content on wood surfaces from a wood maintenance point of view.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1487-1494
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• 2009

The effects of drying temperature (55, 60, and $65^{\circ}C$) and addition levels of maltodextrin (MD) (10, 20, and 30%) on the physicochemical properties and nutritional quality of purple sweet potato flour were investigated. MD-added flours had higher $L^*$ values, water soluble index, total phenolic, and anthocyanin contents than untreated flour. However, $a^*$, $b^*$ values, water absorption index, and swelling capacity were dependent on the drying temperature and MD concentration. On the other hand, untreated flour had a higher ascorbic acid content compared to the MD-treated flour. Ascorbic acid contents decreased, whereas anthocyanin content was not significantly different, with increasing drying temperatures. MD was positively correlated with phenolic content, anthocyanin, hue angle, and water soluble index. However, there was no correlation between quality parameters and glass transition temperature. The best quality product was obtained when samples were pretreated with MD before drying, regardless of drying temperature.

• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.34-42
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• 2016

Purpose: This study was performed to improve the drying quality and drying rate of ginseng slices by combining microwave and far-infrared drying techniques. Methods: Based on single-factor experiments and analyses, a quadratic regression orthogonal rotation combination design was adopted to study the effects of the moisture content at the conversion point between the microwave and far-infrared techniques, the ginseng slice thickness and the far-infrared drying temperature on the chip drying time, the surface color difference value, the nutritional composition and the surface shrinkage rate index. Results: Compared to the far-infrared drying alone, the combined microwave and far-infrared drying resulted in an increase in the saponin content of the ginseng slices and reductions in the drying time, surface color difference, and shrinkage rate. Conclusions: We established a mathematical model of the relationships between the surface shrinkage rate index and the experimental factors using the multi-objective nonlinear optimization method to determine the optimal parameter combination, which was confirmed to be the following: microwave and far-infrared moisture contents of 65%, a ginseng slice thickness of 1 mm, and a far-infrared drying temperature of $54^{\circ}C$.

• Journal of Korean Medicine Rehabilitation
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• v.27 no.1
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• pp.19-25
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• 2017

Objectives Eucommiae cortex is one of the frequently used herbs for musculoskeletal disorders, with well-known anti-inflammatory effect. Meanwhile, powdered form of herbal drugs is more advantageous than decoction form, in that storing and taking is more convenient. Thus, the authors aimed to investigate whether the drying method affects the index compound level and anti-inflammatory effect of eucommiae cortex water extract. Methods Eucommiae cortex was extracted in distilled water at $100^{\circ}C$ for 3 hours, filtered, and then evaporated under vacuum. One half of the sample was freeze-dried at $-80^{\circ}C$. Another half of the sample was added with dextrin and then spray-dried at $180^{\circ}C$. To assess the possible change in index compound content, pinoresinol diglucoside was selected as the index marker. The content level of the index compound in various extract sample was quantified through high performance liquid chromatography. In addition, iNOS assay in LPS-induced RAW 264.7 cells was adopted to determine the anti-inflammatory effect of various extract samples. Furthermore, MTT assay was performed to confirm that the result of iNOS assay was not due to cytotoxicity. Results There was no significance difference in index compound content between extract samples obtained through two different drying methods. Anti-inflammatory activity of extract samples were similar at the matching concentration, regardless of the drying methods. Extract samples did not show any significant cytotoxicity. Conclusions Extract samples of eucommiae cortex were obtained through freeze-drying and spray-drying. Neither change in index compound content nor difference in anti-inflammatory activity was observed between drying methods.

• 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.

• The Korean Journal of Food And Nutrition
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• v.36 no.6
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• pp.496-505
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• 2023

This study explored a method to enhance the drying process usability of local mangoes by producing foam-mat dried powder under varying drying temperatures (50, 60, 70℃) and foam thicknesses (3, 6, 9 mm). The drying process period ranged from 60 to 390 minutes based on the set conditions, with higher temperatures and thinner foams accelerating drying. Powder chromaticity (L^*,(L^*, a^*, and b^*) demonstrated a declining trend with increasing drying temperature and foam thickness, exhibiting notable variance in chroma values. The water absorption index varied significantly, between 3.08 to 4.24, under different drying conditions, although the water solubility index remained consistent across foam-dried samples. Powder moisture content ranged from 2.53% to 3.83%, with hygroscopicity escalating with temperature and foam thickness. Vitamin C structure was compromised during the hot air drying process, especially at temperatures above 60℃. Electronic nose analysis distinguished foam-dried powder from freeze-dried powder; however, a thicker foam yielded a scent profile closer to that of freeze-dried powder. The findings provide fundamental data on mango foam drying, which is expected to improve processing and storage tech for local mangoes.

• Korean Journal of Food Science and Technology
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• v.48 no.1
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• pp.15-19
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• 2016

Drying process was applied to increase the antioxidant activity of onion powder: freeze-drying or air-drying at 50, 70, and $90^{\circ}C$ and onion extracts were obtained from each powder using water or aqueous ethanol (50%) at $25^{\circ}C$ and $60^{\circ}C$. In the color analysis, the freeze-dried powders showed higher $L^*$ and lower $a^*$ and $b^*$ values than did the air-dried ones. The browning index of powders air-dried at $90^{\circ}C$ was significantly higher than that of freeze-dried powders or those air-dried at temperatures below $90^{\circ}C$. Phenolic content in the extracts was 4.02-23.12 mg gallic acid equivalent/g sample, and was the highest in the extract from the sample air-dried at $90^{\circ}C$, regardless of the extraction condition. The highest antioxidant activity, measured by 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid and 1,1-diphenyl-2-picrylhydrazyl methods, was found in the powder air-dried at $90^{\circ}C$, which induced browning. These findings indicate that antioxidant activity depends more on browning during drying than on extraction conditions.

• 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.