• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.3
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• pp.453-459
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• 1996

This study was carried out to determine the changes in quality during the drying process and the optimum drying condition for utilizing soybean curd residue. The quality criteria for soybean curd residue were acid value, peroxide value, fatty acid composition and microbial concentration. The acid values of soybean curd residue were 7.5, 4.5 and 5.9 KOH mg/g upon 12 hour drying with open-air sun, ambient-air blast and warm-air blast, respectively. The numbers of total aerobic bacteria and molds increased remarkably during drying with open-air sunlight, ambient-air blast and warm-air blast except for hot air blast. Among different drying methods, the hot air blast drying(1kg of sample) was the most effective methods, which completed in three hours. Also, the drying method demonstrated a typical drying curve ; settling down, constant rate drying and falling rate drying period were shown within one hour, from one and three hours and after three hours, respectively. Moreover, there was significant variation in the constant drying period for the quality of soybean curd residue.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.7
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• pp.994-1002
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• 2001

In a balance experiment with rats either 0, 25 or 50% of the crude protein (CP) provided as casein in the control diet was replaced with cassava leaves (CL) (Manihot esculenta Crantz) or sweet potato vines (SPV) (Ipomoea balala). CL were either sun-dried or oven-dried at $60^{\circ}C$ or $105^{\circ}C$ or ensiled, while the SPY were either sun-dried or ensiled. The experiment included 3 blocks with 30 rats in each and six individuals per treatment group. Drying at $105^{\circ}C$ resulted in a reduction of the lysine (Lys) content, suggestive of the occurrence of Maillard reactions. Ensiling CL and SPV slightly decreased the CP. content as well as the sum of essential amino acids. The apparent fecal CP digestibility (dCP) and nitrogen retention were negatively affected by increasing the level of replacement (p<0.01 and p<0.001, respectively). The impaired amino acid profile observed when drying CL at $105^{\circ}C$ was found to be related to a slight decrease in dCP (p<0.001) as well as N retention (p<0.005). The effects of sun-drying and oven-drying in reducing the HCN content in CL were more potent than when ensiling. By increasing the total dietary HCN supply serum thiocyanide level, as well as urinary thiocyanate and linamarin output, were increased, with a weak relationship between them. Sun-drying and ensiling with cane molasses as additive successfully preserved the nitrogenous constituents and could be a means of preserving fresh green feed under tropical conditions.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.531-539
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• 2012

To determine the effects of various drying methods on the quality characteristics of beef jerky from low-valued cuts, Hanwoo beef shank muscles were either hot air-dried, shade-dried, or sun-dried. The physicochemical quality and microbiological safety of the Hanwoo beef jerky were analyzed during a storage of $25^{\circ}C$. Moisture content and water activity ($a_w$) of the samples decreased as the time period of storage increased, regardless of the drying condition (p<0.05). Shade-dried jerky showed higher $a_w$ compared to others after storage of 20 d (p<0.05). The pH value of hot air-dried jerky was higher than those of others (p<0.05). For color properties, sun-dried samples showed higher redness ($a^*$) and yellowness ($b^*$) compared with the properties of others (p<0.05). The hot air-dried jerky showed higher shear force values than the sun-dried or the shade-dried jerky after 10 and 20 d (p<0.05). However, the total plate counts (TPCs) of naturally dried jerky (shade and sundried) were higher than hot-air dried jerky after storage of 10 and 20 d (p<0.05). With regard to sensory properties, naturally dried jerky showed higher tenderness, juiciness, and overall acceptability scores than the hot air-dried jerky (p<0.05). In conclusion, although natural drying appears to be more susceptible to microbiological contamination than hot air-drying, the natural drying method seems to result in superior quality than the hot air drying method.

• Korean Journal of Food Science and Technology
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• v.24 no.5
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• pp.428-439
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• 1992

Drying process in a fixed bed red pepper dryer was modeled and simulated. Drying efficiency describing the effectiveness of energy usage in red pepper drying was defined as a ratio of energy used for moisture evaporation to total energy consumption, and expressed in combination of measurable temperature variables. The efficiency was compared with real evaporative efficiency and tested in the simulated and experimental drying. An overall drying efficiency was derived, and analyzed for various control variables consisting of drying temperature, air recycle ratio and air flow rate. Optimal operation conditions of drying was then searched by Box's complex method by using it as an objective function. Carotenoids retention was simulated and put as a constraint of product quality in the optimization. The optimization results gave that two staged drying operation could improve the ding efficiency compared with single staged drying. As a technique for further energy saving automatic termination of drying appeared feasible by monitoring an exit air temperature from dryer.

• Korean Journal of Food Science and Technology
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• v.16 no.1
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• pp.78-82
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• 1984

Effects of various drying conditions of agar gel on the physico-chemical properties of dried agar were investigated. For drying of the agar gel$(1.0{\times}1.0{\times}34.0cm)$ by means of sun drying, simple solar drying, hot-air drying ($30^{\circ}C$, control, natural convection), hot-air drying ($30^{\circ}C$, pretreatment, natural convection) and freeze drying, it took 96, 75, 67, 50 and 21 hours, respectively. The gel strengths of dried agar gel prepared by sun drying, solar drying, freeze drying and spray drying were320, 370, 270 and $360g/cm^2$, respectively and that of hot air-dried agar gel was influenced by drying temperature, pretreatment an mode of heat transfer. The gel strength, the gelation temperature and other quality index of spray-dried agar were not inferior to those of sun-dried agar, but it was not expected to be economical because of it recovery rate. In case of hot air drying, the gel strength value of agar increased as the drying rate increased. No significant differences among various products were noted in the gelation temperature, the melting temperature, the ash and $SO_3$ content.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1464-1469
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• 2009

Jiwhang (Rehmannia glutinosa), one of the most widely used medicinal herbs, was dried with various methods such as sun drying, hot air drying, vacuum drying, and freeze drying methods, and their effects on the antioxidant capacity in relation with the content of total phenolic compounds were studied with a steamed-and-dried rehmannia (sookjiwhang) for comparison. Generally, total phenolic contents decreased significantly by all of the drying treatments except the steamed-and-dried rehmannia, in which total phenolic contents increased 2.4 fold compared with fresh rehmannia. Content of verbascoside, a functional phenolic compound, was the highest in the freeze-dried rehmannia ($177.97{\pm}0.02\;{\mu}g/g$ d.m.) followed by vacuum-dried ($105.55{\pm}0.07\;{\mu}g/g$ d.m.), hot air-dried ($23.01{\pm}0.02\;{\mu}g/g$ d.m.), and sun-dried ($4.89{\pm}0.13\;{\mu}g/g$ d.m.) ones comparable to the fresh rehmannia ($80.15{\pm}1.26\;{\mu}g/g$ d.m.). Antioxidant capacity determined by both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis (3-ethyl-benzthiazoline-6-sulphonic acid) (ABTS) methods agreed with the result of total phenolic contents, that is, the antioxidant capacity was the highest in the steamed-and-dried rehmannia followed by fresh rehmannia, vacuum-dried, hot air-dried, sun-dried, and freeze-dried ones. Conclusively, the total phenolic contents and antioxidant capacity of rehmannia were greatly affected by the drying methods used.

• Food Science and Preservation
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• v.12 no.5
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• pp.436-441
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• 2005

This study was observed the effects of drying methods on the extraction characteristics of Rubi fructus (fruits of Rubus coreanus). Extraction yields of soluble solids and total sugar were high in the Rubi fructus dried by freeze drying, followed by infrared drying and sun drying. Extraction yield of phenolic compounds and DPPH radical-scavenging activity of extracts were in the following order; the Rubi fructus dried by freeze drying, the Rubi fructus dried by infrared drying, the Rubi fructus dried by sun drying. L value was the highest in the Rubi fructus dried by freeze drying, and a and b value were lowest in the fruit dried by freeze drying. These results suggest that freeze drying has an beneficial effect to enhance the quality of Rubi fructus. Water and ethanol extractions was more effective in the extraction of soluble solids and the antioxidative components.

• Journal of Biosystems Engineering
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• v.33 no.6
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• pp.390-395
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• 2008

Current high oil price and the agreement on global climate change prevention have increased worldwide investment and research on renewable energy. In Korea, development of a rapeseed dryer for bio-diesel production has been started in 2007. Usually, rapeseeds are harvested in early summer, because rice cultivation is followed right after rapeseed harvesting. Early harvest and bad summer results in highly moistured rapeseed and development of artificial drying system is required to dry great amount of rapeseed that couldn't be processed by sun drying alone. The rapeseed dryer was modified from an existing circulation type grain dryer. Modification of the dryer was performed with the aid of CFD simulation. Drying test showed that drying rate of rapeseed was 1.51%/h and germination rate reduction was 4.5%p for the drying temperature of $60^{\circ}C$.

• Food Science and Preservation
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• v.13 no.1
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• pp.37-42
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• 2006

In recent, Kimchi is produced in the scale of industry, Consumers show increased demand of safety and high quality and hygienic process control. So, sun drying, hot air drying and cold air drying methods were investigated to compare the demand Sun drying took 96 hrs, hot air drying took 4 hrs at $70^{\circ}$ and cold air drying took 102 hrs at $10^{\circ}C$ in removing water to $90\%$ from radish. Brownness of radish was expressed as absorbance. Absorbance were 0.20, 2.04 and 1.87 and also Vit-C contents were 0.14 mg/g, 0.12 mg/g and 0.096 mg/g in dried radish according to cold air drying, hot air drying and sun drying, respectively. From overall experimental results, cold air drying method was found as superior drying method to other drying methods.

• The Journal of Natural Sciences
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• v.14 no.1
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• pp.139-149
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• 2004

It was aimed to find out an efficient method of drying hot pepper, of which powder is used as one of the main ingredients in Korean dish preparation including Kimchi. Before sun or heat drying fruits harvested were horizontally cut into three pieces punched with an auger of 4 mm in diameter, or used as the whole fruit. Various drying methods were used including sun drying, drying under a plastic house, sun drying after heat drying for 5 hours at $70^{\circ}C$, $80^{\circ}C$, or $90^{\circ}C$, heat drying only at $50^{\circ}C$, $60^{\circ}C$, or $70^{\circ}C$, and changing temperature of $70^{\circ}C$, $5hours+60^{\circ}C$ until coplete dry, $80^{\circ}C+60^{\circ}C$, or $90^{\circ}C+60^{\circ}C$. The results are summarized as follows. With sun drying of the whole fruit, in required about 10days to reach the satisfactory level of dryness as indicated by its moisture content of below 10% in general. In case of heat drying combined with sun drying, it required 5 to 7 days. For cut fruits, it required 1 or 2 days less than for whole or pinholed fruits until drying. Under heat of alternation temperature drying, cut fruits also dried 15-20 hours earlier compared with whole of pinholed fruits. There were not significant differences for the recovery rate of the fruit with various drying methods. The occurrence of white fruits, which are caused by one of physiological disorders during drying, and rotten fruits was reduced with the cut fruit drying. The damages were very high with the PE house drying, but very little with the heat drying.