• Culinary science and hospitality research
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• v.19 no.2
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• pp.40-51
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• 2013

In this study, frozen mulberries were dried with the methods of freeze-drying and hot-air drying and powdered to make healthy functional bagels by adding 0% (control), 1%, 3%, 5%, and 7% of mulberry powder. After measuring the general ingredients, physiochemical property, total polyphenol content and DPPH radical scavenging of frozen mulberries, the physiochemical property test and sensory test of manufactured bagels were carried out. The pH of the bagels appeared to be higher in the group with the addition of hot-air dried mulberry powder than in the group with the addition of freeze-dried mulberry powder. Luminosity (value L) and yellowness index (value b) appeared to be higher in the group with the addition of hot-air dried mulberry powder than in the group with the addition of freeze-dried mulberry powder. Redness index (value a) appeared to be higher when freeze-dried mulberry powder was added than when hot-air dried mulberry powder was added. Hardness showed a significant difference in the group with the addition of freeze-dried mulberry powder while the group with the addition of hot-air dried mulberry powder showed the opposite result. Elasticity did not have any significant difference in the group with the addition of hot-air dried mulberry powder while it showed a significant difference in the group with the addition of freeze-dried mulberry powder. Cohesiveness did not show any significant difference and gumminess showed the tendency of decrease as the added quantity of freeze-dried mulberry powder and hot-air dried mulberry powder increased. The preference of the group with the addition of 5% freeze-dried mulberry powder and the group with the addition of 3% hot-air dried mulberry powder appeared to be the highest.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.575-580
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• 1999

In this study, the quality changes of Hoelen was investigated, which were color differences, browning degrees, total phenolic compounds and electron donating abilities to optimize drying condition using hot air and far infrared drying by changing conditions such as temperatures, air velocities and radiation distances. In color values, ${\Delta}b\;value$ decreased with increasing temperatures, while ${\Delta}L$, ${\Delta}a$ and ${\Delta}E\;value$ increased. The browning degrees showed the similar tendency with the color values. Total phenolic components of Hoelen decreased with increasing drying temperature and air velocity, and decreasing radiation distance. On the other hand, there was no significant difference in the changes of electron donating abilities (EDA) of Hoelen among drying methods and conditions. As a result, the hot air drying was more effective method than the far infrared was.

• Food Science and Preservation
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• v.22 no.1
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• pp.1-11
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• 2015

Raspberries are a good resource of polyphenols and have a powerful antioxidant activity, but shelf life for raspberries is short which brings a lot of economic losses. In this study, we try to use cool-air ($20{\sim}40^{\circ}C$) or hot-air ($60{\sim}100^{\circ}C$) to produce semi-dried raspberries with extended shelf life, and to determine the best method for improving fruit quality by minimizing nutrient losses during drying processes. The effects of process variables (drying temperature and processing time) on the quality of final dried raspberries were investigated. Response surface methodology was employed to establish statistical models for simulating the drying processes, and the moisture residue content and the loss ratios of total phenolic content (TPC), vitamin C (VC), and ellagic acid (EA) that result from the drying processes of raspberries using either hot or cool-air were predicted. Superimposed contour plots have been successfully used in the determination of the optimum zone within the experimental region. Optimal conditions determined for achieving minimal losses of TPC, VC, and EA, and a final moisture residue of 45% using the hot-air drying process were a drying temperature of $65.75^{\circ}C$ and a processing time of 4.3 hr. While for the cool-air process, the optimal conditions predicted were $21.3^{\circ}C$ and 28.2 hr. Successful application of response surface methodology provided scientific reference for optimal conditions of semi-drying raspberries, minimizing nutrient losses and improving product quality.

• Applied Biological Chemistry
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• v.32 no.3
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• pp.278-285
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• 1989

Effects of cooking and drying methods on the taste component and microstructure of shrimp, Metapenaeus joyneri, were investigated. The nucleotides and their related compounds of fresh shirmp such as ATP, ADP, AMP, IMP, inosine and hypoxanthine were detected. AMP was detected as a trace amount in fresh shrimp, however, it increased up to $23.5{\sim}45.7{\mu}$ moles with cooking and drying due to the decomposition of ATP and ADP to AMP during cooking and drying. The major component of the free amino acids of fresh shrimp was arginine followed by glycine, lysine, proline and alanine. These free amino acids contents were 70% of the total free amino acids. One hundred grams of fresh shrimp contained 1,198mg (dry basis) of the total free amino acids. However, for hot air and freeze dried cooked shrimps it was decreased down to 342mg (dry basis) and 503mg (dry basis), respectively. It might be due to the dissolution of soluble amino acids during cooking. Hot air-and freeze-dried fresh shrimps was higher in hardness and brittleness but lower in cohesiveness and gumminess than hot air-and freeze-dried ones with boiling and microwave heating. Freeze dried shrimp had softer myofibril texture than hot air dried one. At the same time, more dense and multiporous structure in the tissue could be obtained from the hot air and freeze drying, respectively, after microwave heating of shrimps.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.467-474
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• 2021

The renewable energy is known as eco-friendly energy to reduce the use of fossil fuel and decrease the environmental pollution due to exhaust gas. Targets of solar collector in domestic are usually acquisitions of hot water and hot air. System of air-heating collector is one of the technologies for obtaining hot air in cases of especially heating room and drying agricultural product. The purpose of this study is to investigate the characteristics of thermal flow such as relative pressure, velocity, outlet temperature and buoyancy effect in air-heating collector using solar heat. The flow field of air-heating collector was simulated using ANSYS-CFX program and the behaviour of hot air was evaluated with SST turbulence model. As the results, The streamline in air-heating collector showed several circular shapes in case of condition of buoyancy. Temperature difference in cross section of outlet of air-heating collector did not almost show in cases of buoyancy and small inlet velocity. Furthermore merit of air-heating collector was not observed in cases of inlet velocities. Even though it was useful to select condition of buoyancy for obtaining high temperature, however, it was confirmed that the trade off between high temperature of room and rapid injection of hot air to room could be needed through this numerical analysis.

• Journal of Biosystems Engineering
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• v.37 no.5
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• pp.327-334
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• 2012

Purpose: The color changes in red pepper during far infrared drying were studied in order to establish a color change model. Methods: The far infrared drying experiments of red pepper were conducted at two temperature levels of 60, $70^{\circ}C$ and two air velocity levels of 0.6 and 0.8 m/s. The results were compared with the hot-air drying method. The surface color changes parameters of red pepper were measured qualitatively based on L (lightness), a (redness), b (yellowness) and total color changes (${\Delta}E$). The goodness of fit of model was estimated using the coefficient of determination ($R^2$), the root mean square error (RMSE), the mean relative percent error (P) and the reduced chi-square (${\chi}^2$). Results: The results show that an increase in drying temperature and air velocity resulted in a decrease in drying time, the values of L (lightness) and a (redness) decreased with drying time during far infrared drying. The developed model showed higher $R^2$ values and lower RMSE, P and ${\chi}^2$ values. Conclusions: The model in this study could be beneficial to describe the color changes of red pepper by far infrared drying.

• Korean Journal of Food Science and Technology
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• v.40 no.1
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• pp.36-41
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• 2008

This study was conducted to investigate the effects of combined osmotic dehydration and hot-air drying on the quality of dried apple products. Apple cylinders were steeped in 30% and 50% sucrose solutions at different steeping times. During the osmotic dehydration, as the concentration of the sucrose solution and steeping time increased, weight reduction and water loss increased, and the solid gain showed similar results. Osmotic dehydration in the sucrose solutions was followed by hot-air drying at 50 and $70^{\circ}C$. The experimental data were fitted successfully using the modified Page model. At the drying temperature of $50^{\circ}C$, the drying time increased from 4.15 hr for the control to 5.78 hr and 6.42 hr for the 30 and 50% sucrose solution treatments, respectively. Similar results were shown at the $70^{\circ}C$ drying temperature. The k and n values of the apple cylinders decreased by osmotic dehydration, and the k and n of the apple cylinders steeped in the 50% sucrose solution were lower than those of the samples steeped in the 30% sucrose solution. The qualities of the dried apple products were compared to samples that did not undergo osmotic dehydration. The shrinkage and rehydration capacity of the apple products decreased via osmotic dehydration, and decreased as the concentration of the sucrose solution increased. The compressibility ratios of the apple products to raw apple cylinders increased by osmotic dehydration, and increased as the concentration of sucrose solution increased. The sensory evaluation results for the apple products rehydrated in yoghurt indicate that osmotic dehydration greatly enhances the palatability of apple products in terms of appearance, taste, and texture.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.417-420
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• 1993

Changes in color intensity of Hololeion maximowiczii(HM) roots which were treated with freeze drying (FD), $50^{\circ}C$ hot air drying (HAD) and $50^{\circ}C$ hot air drying after steam blanching (HADB) were investigated in this study. Color of HADB was yellow-green while other treatments showed bright brown color. In brown color intensity, optical density at 420 nm of FD treatment was highest but HADB treatment showed the highest value in ultra violet spectrum. Water soluble pigment of HM in state of aquous solution was more unstable for heat treatment than that in state of powder. Activation energy for decomposition of the pigment was 20.9 kcal/mole between $90{\sim}100^{\circ}C$ but 50.6 kcal/mole between $80{\sim}90^{\circ}C$.

• Food Science and Preservation
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• v.5 no.3
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• pp.217-223
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• 1998

Quality and component of dry Omija during storage and shelf-life of fresh Omija were investigated. Acidity and pH of dry Omija were not significantly different among drying methods, but reducing sugar(3.77%) of field (drying was much lower than that of hot air drying(11.02%) and freeze drying(10.12%). Crude protein was higher in order of freeze drying> hot air drying> field drying, and the optical density of freeze drying at 520nm were higher up to about 3 times than field drying and hot air drying, respectively. Moisture content of dry Omija during the storage was increased, whereas acidity decreased at 25$^{\circ}C$. However changed little at 4, -5, -20$^{\circ}C$ Reducing sugar increased until 8 mouth, and thereafter decreased continuously. Optical density and color(L,a,b) decreased at 25$^{\circ}C$ but increased at 4, -5, -20$^{\circ}C$. Shelf-life of flesh Omija at 4$^{\circ}C$ was limited to 9 days because staring decay. Acidity and reducing sugar of flesh Omija continuously decreased during storage at -5, -60$^{\circ}C$. Optical density increased until 8 month and then decreased, and especially the optical density of 8 month storage at -60$^{\circ}C$ was higher than initial's.

• Applied Biological Chemistry
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• v.32 no.3
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• pp.286-294
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• 1989

Effects of cooking and drying methods on the quality of shrimp, Metapenaeus joyneri, were investigated. The cholesterol content of fresh shrimp was 81.4mg/100g of dry basis. It was $5{\sim}28%$ less in freeze dried shrimps as compared to hot air dried shrimps. The volatile basic nitrogen and trimethylamine contents of hot air dried shrimp was higher than those of freeze dried one, but total viable count of freeze dried shrimp was lower than that of hot air dried one. The color of cooked-shrimps was much brighter than uncooked-fresh shrimp. Freeze dried shrimp was lighter than hot air dried one. Total color difference $({\Delta}E)$, however, was opposite to its lightness. The mineral component of fresh shrimp was composed of calcium predominantly, followed by potassium and sodium, which were 96% of the total mineral contents. Cooking and drying methods did not affect the mineral content.