• Food Engineering Progress
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• v.21 no.1
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• pp.42-48
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• 2017

The purpose of this study was to verify the drying characteristics of steamed sweet potato and to establish optimal drying conditions for far-infrared drying of steamed sweet potato. 4 kg of steamed sweet potato was sliced to thicknesses of 8 and 10 mm, and dried by a far-infrared dryer until a final moisture content of $25{\pm}0.5%$. The far-infrared dryer conditions were an air velocity of 0.6, 0.8 m/s and drying temperature of 60, 70, and $80^{\circ}C$. The results can be summarized as follows. The drying time tended to be reduced as temperature and air velocity for drying increased. The Lewis and Modified Wang and Singh models were found to be suitable for drying of steamed sweet potato by a far-infrared dryer. The color difference was 35.09 on the following conditions: Thickness of 8 mm, temperature of $80^{\circ}C$, and air velocity of 0.8 m/s. The highest sugar content ($59.11^{\circ}Brix$) was observed on the conditions of a thickness of 8 mm, temperature of 80, and air velocity of 0.8 m/s. Energy consumption decreased on the conditions of higher temperature, slower air velocity, and thinner steamed sweet potato.

• Korean Journal of Food Science and Technology
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• v.40 no.4
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• pp.466-469
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• 2008

This study examined the effect of drying temperature on the qualitative properties of Chrysanthemum boreale M. flowers. The flower samples were dried in a hot air dryer at $40^{\circ}C$, $50^{\circ}C$, and $60^{\circ}C$, respectively, to attain a $23{\pm}1%$ moisture content. The time required to reach the target moisture content was 8.5-69 hr, and there was a very high negative correlation between log (spending time) and temperature. The Hunter color L- and b-values of the flowers were decreased with increasing drying temperature, whereas the a-value was increased. The volatile compounds contained in the dried flowers were determined by a solid-phase microextraction method. Twelve primary volatile compounds were detected and then quantified based on the GC chromatograms of the samples. The total contents of volatile compounds were increased with increasing drying temperature, and germacrene D and camphor were the main compounds in all samples.

• Food Science of Animal Resources
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• v.18 no.2
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• pp.176-184
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• 1998

The objective of this study was to investigate the effects of freezing rate on aroma retention and to examine the mechanism of aroma retention during freeze drying process. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80${\times}$20mm) containing diacetyl(2mg/ml) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\circ}C$ and followed with freeze-drying. Under the upper conditions we measured freezing rate and the change of temperature and pressure during freeze drying. Freeze-dried gelatins were cut horizontally into 5 mm thickness from the bottom measured and diacetly contents. Besides, we observed the effect of the relative humidity of the diacetyl contents freeze-dried gelatin during storage. The retained diacetyl content was increased at high freezing temperature and in order of 0∼5, 5∼10, 10∼15, 15∼20 mm section from the bottom of the sample. It was observed that the retained diacetyl content was high in 15∼20 mm section. The retained diacetyl content and freeze-dried gelatin stored in the condition of high relative humidity was decreased significantly but in the low relative humidity case, was it decreased in small amount. The results of our experiment resents that the low temperature freezing and low humidity storing condition is effective for preserving aroma compound in food.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.9
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• pp.1304-1308
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• 2000

A total of thirty-six gilts $(24.78{\pm}1.39kg)$ were employed for 38 days (Exp. 1), and twenty-four gilts $(46.50{\pm}1.90kg)$ for 43 days (Exp. 2) to determine growth performance and carcass characteristics in pigs fed dried food waste (DFW). Pigs were allocated by dietary treatments: 0%, 20% and 40% DFW. For nutrient digestibility, twelve female pigs $(50.20{\pm}0.52kg)$ were used in individual pens to collect feces. Food wastes were collected from restaurants and apartment complex areas and dried in a drum-type dryer at $115{\pm}2{^{\circ}C}$. Experimental diets for feeding trials were formulated to contain 3,400 kcal DE/kg and 17% crude protein. The tested DFW contained 2,858 kcal DE/kg, 25.0% crude protein, 17.3% crude fat, 1.37% Ca, 1.28% P, and 3.28% NaCl. As compared to crude protein content, the limiting amino acids (i.e., 0.90% lysine and 0.52% methionine) were low. The digestibilities of energy, ash, calcium and phosphorus in the DFW were generally lower than those in the grower diets, but the digestibilities of crude protein and crude fat were higher in DFW than the grower diet. Feeding DFW in pigs had a linear (p<0.01) effect on ADG and feed/gain as the inclusion levels of DFW were increased (Exp. 1). The ADG of pigs fed 40% DFW was also poorer (p<0.05) than that fed the control diet (Exp. 2). Carcass characteristics in terms of backfat and dressing percentage were not affected by dietary treatments. In conclusion, it seems that the optimal dietary inclusion level of the DFW is about 20% in the diet for growing-finishing pigs.

• Korean Journal of Food Science and Technology
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• v.14 no.4
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• pp.342-349
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• 1982

Filefish muscle in the form of thin plate $(5{\times}10{\times}0.4\;cm)$ was dried in a forced air dryer at $47.5^{\circ}C$ to study the relation between dehydration mechanism and water activity. The dryer was designed in such a way that the temperature, relative humidity and velocity of air could be controlled. The whole dehydration process of the filefish muscle was divided into two different drying rate periods, constant and falling rate period. During the constant drying rate period, the drying rate was proportional to the square root of air velocity under the conditions of constant temperature and relative humidity of air. The falling rate period was further divided into two different falling drying rate periods, first and second falling rate period. The first falling rate period was an unsaturated surface drying period caused by partial unsaturation of the drying surface with capillary condensed free water diffused from the internal part of the filefish muscle. At this stage he drying rate was mainly dependent on the relative humidity at constant air temperature, and case-hardening phenomenon started at the end of this stage. The moisture content and the water activity at which the second falling rate period started were not constant, because the drying rate of the first falling rate period was strongly dependent on the air humidity. The second falling rate period was again divided into two drying rate periods, former and latter period. The drying rates of both of these periods were independent on the external air humidity. During the former period of the second falling rate period, the dehydration was proceeded by diffusion and vaporization of capillary condensed free water in filefish muscle. The diffusion coefficient of water was $2.89{\times}10^{-10}m^2/sec\;at\;47.5^{\circ}C$. At this stage, the case-herdening continued until the water activity reduced to 0.7. The latter period of the second falling rate period started at the water activity of 0.45. The dedydration was proceeded by diffusion and vaporization of bound water, which adsorbed in multimolecular layers, through the hardened drying surface. The number of molecular layers was 4, and the diffusion coefficient of water during this stage was $4.38{\times}10^{-11}m^2/sec\;at\;47.5^{\circ}C$.

• Journal of Biosystems Engineering
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• v.36 no.4
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• pp.273-278
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• 2011

This study was carried out to define the optimum drying conditions for Lycium chinense Miller as a useful healthy food, because recently the cultivation area and yield of this fruit are increased. The experiments of two varieties were performed at the temperature of $45^{\circ}C$, $50^{\circ}C$, $55^{\circ}C$ and $60^{\circ}C$. The drying ratio was the slowest and quality was the best at the drying temperature of $45^{\circ}C$. The drying temperature was higher, drying ratio was more faster and the quality became worse. The difference of drying ratios between the varieties was insignificant. The energy consumption per hour was the minimum at the drying temperature of $45^{\circ}C$, but the total energy consumption was the maximum for the long drying time. Also, the energy consumption at the drying temperature $50^{\circ}C$, $55^{\circ}C$ and $60^{\circ}C$ was not very different from others. Considering the drying ratio, quality and energy consumption, the drying time of 36 hours at the drying temperature of $50^{\circ}C$ was the most optimum condition.

• Culinary science and hospitality research
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• v.13 no.2
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• pp.1-11
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• 2007

The process of Cheonggukjang powderization and application to the western food recipes were established. Cheonggukjang was made and processed into the powder. The optimum condition of Cheonggukjang solution for the powdering process was 50%(w/w). And it was completely grinded by a mixer. Drying condition of a spray dryer was to be injected 1 mL/sec. in $105^{\circ}C$ with 3,000 rpm. The components of Cheonggukjang were 49.7 g/100 g of moisture, 2.6 g/100 g of crude ash, 16.2 g/100 g of crude carbohydrate, 23.4 g/100 g of crude protein, 8.1 g/100 g of crude fat, and 9.3 g/100 g of cellulose. The major amino acid was glutamic acid and its quantity was 4,345.5 mg/100 g. And the next were aspartic acid (2,539.2 mg/100 g) and leucin (1,963.2 mg/100 g). In application, 4 kinds of soup recipes using Cheonggukjang powder were developed. The sensory test showed the acceptability between the soup with the powder and the soup without the powder was significant at odor(p<0.05) in vegetable cream soup and broccoli soup, and at taste(p<0.01) in vegetable cream soup. And the soup with non powder showed more acceptability.

• Food Science of Animal Resources
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• v.18 no.2
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• pp.164-175
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• 1998

The objective of this study was to investigate the effects of freezing rate on ice crystal size and freeze-drying rate. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80$\times$20mm) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\circ}C$ and followed with freeze-drying. Under the upper conditions we measured freezing rate and the change of temperature and pressure during freeze drying. Freeze-dried gelatins were cut horizontally into 5 mm thickness from the bottom and measured their pore sizes. Also freeze-drying rate(primary drying) is estimated by measuring the temperature of sample and pressure of vacuum chamber. During freeze-drying, profiles of pressure and temperature were shown constant tendency regardless of freezing temperature and we could expect the end-point of freeze drying by considering pressure and temperature together. In temperature profiles, the point which temperature increased significantly was observed during freeze-drying. There is no relationship between freeze temperature and drying rate of primary drying in our model system. As freezing temperature increased, ice crystal size(X*) which correspond to 63.2% of cumulative frequency was increased and at the same freezing temperature ice crystal size(X*) was decreased with distance from the bottom of the sample. Freezing conditions have a strong influence on the quality of the final freeze-dried products in freeze-drying system.

• Journal of the Korean Society of Food Culture
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• v.35 no.6
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• pp.590-596
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• 2020

Buckwheat (Fagopyrum species) has long been an excellent functional food. Besides, buckwheat sprouts contain various functional substances. In this study, we investigated the antioxidant activity of buckwheat sprouts in the context of cultivars harvested after different cultivation periods (0, 3, 5, 7, 9, 13, and 15 days after planting). Buckwheat sprouts were cultivated at 25℃ for up to 15 days and then extracted with ethanol. Antioxidant components were then extracted from sprouts and leaves using a freeze dryer. The total polyphenolic content, flavonoid content, and antioxidant activity were then analyzed. The total polyphenol content increased from 32.26 mg GA eq/100 g for raw buckwheat to 114.75 mg GA eq/100 g after 7 days of cultivation. Also, the flavonoid content increased from 20.61 mg catechin eq/100 g (0 days) to 56.54 mg/g after 9 days of cultivation. The DPPH radical scavenging activity (concentration of extract at 0.25 mg/mL) increased from 7.89% at day 0 to 53.48% after 9 days of cultivation. Additionally, the ABTS radical scavenging activity increased from 10.26% at day 0 to 32.89% after 7 days of cultivation; of note, the activity decreased afterward. These results suggest that the best buckwheat sprouts with higher biological activities are those cultivated for 7-9 days. For a complete understanding of the potential of buckwheat sprouts as functional foods, we plan to further analyze their antioxidant activity in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.460-469
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• 2010

In spite of the global-class aquaculture and fishing technology of our country, the processing technologies are lags behind the other nations relatively. The processed marine products are mainly frozen foods, canned goods, salty food (fermented fish products), fish paste products (boiled fish paste), and we can see that the high-value dehydrated foods by drying are very few. These problems are considered to be caused directly by the lack of drying technologies. This paper is concerned to the experimental results of drying heat transfer characteristics for the green energy type vacuum dryer for the high quality sea foods production.