• Journal of the Korean association of regional geographers
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• v.2 no.1
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• pp.133-150
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• 1996

This study is to clarify the market cycle of travelling merchants and the spatial behavior of consumer's commodity purchasing. its reasons and purchasing region of each commodity in Chongsan of Chongsan Myun(village) periodic markets, that is one of the lowest central places in Okchon county. The data used are the results of interviews with 58 travelling merchants on June 22 and July 17, 1994, and questionaire survey taken to parents of students of Chongsan middle school of Chongsan Myun in Okchon county. Study area is typical agricultural regions taking the role of central places to provide rural service and is comparatively important periodic markets. Some of findings are summarized as follows: (1) Until 1980's. appearance of closed periodic markets is caused by the population decrease in rural region, income increase, and rising of living level according to the Five Years Planning of Economic Development, appearance of chain stores of agricultural co-coperative and of supermarkets,. changes in distribution mechanisim by increasing consignment volume of agricultural products through agricultural co-coperative, and the development of transportation in Okchon county. These, too, became the reasons for the decline of the Chongsan periodic markets in Okchon county. (2) Most of the travelling merchants visiting the Chongsan periodic markets are in their 50's of age, and they sell the miscellaneous commodities and agricultural products. And about one-fourths of travelling merchants reside in regions with periodic markets and in Okchon of higher order central places. (3) Travelling routes visting periodic markets can be simplified to five types. Major types of travelling routes are Chongsan periodic market$\rightarrow$Wonnam$\rightarrow$Boun, and Chongsan periodic market$\rightarrow$Yungdong$\rightarrow$Yongsan. The patterns of travelling merchants visiting periodic markets are classified into the type of everyday visiting of periodic markets over three days of five days from merchant's residence to market, and the type of merchants or consumers visiting one day's of five days. On days that travelling merchants don't visit periodic markets they purchase the commodities in Seoul, Taejon and Chongju. (4) Consumers who use periodic markets are from thirties to fifties years of age and most of them are employed in agriculture. Consumers visit periodic markets on foot or by bus, and visit two or three times in a month, and mainly purchase the commodities for one or two hours from about ten o'clock in the morning. (5) Consumers purchase the necessaries of life in periodic markets, and other commodities are purchased in Taejon city, Youngdong, and Boun Eup(town). But consumers purchase the goods(convenience goods, shopping goods, and specialied goods) largerly in Chongsan, because additional expense and disadvantage after service with poor transportation service for purchased goods in others regions. Therefore, the hierarchies of central places by the consumer's purchasing behaviour can not be seem in dewellers in Chongsan and Chongseong Myun.

• Korean Journal of Food Science and Technology
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• v.47 no.3
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• pp.306-320
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• 2015

This survey was carried out in 2014 to estimate the pesticide residue levels in commercial environment-friendly agricultural products in Seoul metropolitan area. Pesticide residues in 27 commodities were examined and analyzed using LC-MS/MS, which can simultaneously detect up to 85 pesticides. A total of 441 samples were collected and analyzed. Among the detected samples, the residue levels in 1.2% of organic agricultural products and 2.2% of pesticide-free agricultural products exceeded the maximum residue limits (MRLs); hence, 1.8% of the total samples exceeded the MRLs. The safety of the detected pesticides was assessed by monitoring the acceptable daily intake level (ADI) and acceptable dietary exposure (ADE) to the pesticides via consumption of the commodities. ADI and ADE are found to be 0.07728-9.46530% and 0.00141-0.17210%, respectively, which means that the residual pesticides in the environmental-friendly agricultural products in Korea are below the safe limit and therefore, pose no potential public health risks.

• Korean Journal of Agricultural Science
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• v.33 no.2
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• pp.129-140
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• 2006

There are need to develop of merchandise of value added fresh ginseng because of high consciousness level of consumer and enlarge of markets for high quality products. The fresh ginseng after harvest was distributed to farmer partually but in general, it was to market by consigner or wholsaler directly after harvest. There were a high difference on storage period of fresh ginseng in different harvesting seasons. The reduction of value of commodities of fresh ginseng for storage period was caused by decomposition and tender of tissue. The storage temperature was under the freezing point and the packing method was sealing tightly by plastic film. As the quality of fresh ginseng was defined by naked eye, it was difficult to sort the quality of ginseng directly harvest.

• Korean Journal of Environmental Agriculture
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• v.34 no.2
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• pp.111-119
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• 2015

BACKGROUND: Ethychlozate (ECZ) is a plant growth regulator of synthetic auxin for agricultural commodities (ACs). Accurate and sensitive method to determine ECZ in diverse ACs on global official purpose is required to legal residue regulation. As the current official method is confined to the limited type of crops with poor validation, this study was conducted to improve and extend the ECZ method using high-performance liquid chromatography (HPLC) in all the registered crops with method verification. METHODS AND RESULTS: ECZ and its acidic metabolite (ECZA) were both extracted from acidified samples with acetone and briefly purified by dichloromethane partition. ECZ was hydrolyzed to form ECZA and the combined ECZA was finally purified by ion-associated partition including hexane-washing. The instrumental quantitation was performed using HPLC/ FLD under ion-suppression of ECZA with no interference by sample co-extractives. The average recoveries of intra- and inter-day experiment ranged from 82.0 to 105.2% and 81.7 to 102.8%, respectively. The repeatability and reproducibility for intra- and inter-day measurements expressed as a relative standard deviation was less than 8.7% and 7.4%, respectively. CONCLUSION: Established analytical method for ECZ residue in ACs was applicable to the nation-wide pesticide residues monitoring program with the acceptable level of sensitivity, repeatability and reproducibility.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.1
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• pp.117-126
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• 1984

Aflatoxins are toxic and carcinogenic secondary metabolites which are produced by trains of A. flavus and A. parasiticus during their growth on foods and feedstuffs. Aflatoxins are a group of closely related heterocyclic compounds of which $B_1$, $B_2$, and $G_2$ are the major members. Aflatoxins are synthesized via a polyketide pathway in which the general steps are acetate, an-thraquinones, xanthone and aflatoxins. Aflatoxin formation is favored by high moisture or high $a_w$(0.95${\sim}$0.99). The limiting $a_w$ for aflatoxin production on agricultural commodities is 0.83. Optimum temperature for aflatoxin production by the molds is $25{\sim}30^{\circ}C$ and the incubation time for the maximum production of the toxin is 7${\sim}$15 days. The limiting temperatures for aflatoxin production are ${\leq}7.5^{\circ}C\;and\;\geq40^{\circ}C$. Cycling temperatures may or may not stimulate aflatoxin production depending on the amplitude of cycling, substrate and strains of molds. Aflatoxin pro-ducing molds are aerobic organisms and thus have a requirement for oxygen. A decreasing $O_2$ concentration and/or increasing concentrations of $CO_2$ or $N_2$ depress the mold growth and aflatoxin formation. A. flavus grows competitively or associatively in the presence of other microorganisms and occasionally loses the competition with other microorganisms. Some lactic acid bacteria have been shown to reduce growth and aflatoxin production by A. parasiticus. Carbon source is the most important nutritional factors affecting aflatoxin formation by the molds. Sucrose, fructose and glucose are the most favorable carbon sources. Food substrates of plant derived products which have high carbohydrate content such as agricultural commodities and their products are most vulnerable to contamination by aflatoxins.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2002.08a
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• pp.46-53
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• 2002

The self-sufficiency of rice production was attained in 1975 through development of Tongil-type high-yielding rices and rapid dissemination to farmers and innovation of cultivation technologies, so-called "green revolution" in Korea. It can be continued during the last twenty seven years except some years with meterological disasters. The national average of milled rice yield per ha was only 3.1 ton at the first half of 1960′s, but it drastically increased to 5.0 ton at the 2nd half of 1990′s. Also, the rice quality was highly improved through the continuous varietal improvement of high-yielding japonica rice cultivars. The amounts of rice stock will go beyond about 1.9 million tons in 2002 due to the recent continuos bumper rice crop and relatively rapid reducing in rice consumption. There are so many rice brands over 1,200 in Korea, but most of rice commodities are not enough controlled in terms of marketing quality and palatability of cooked rice. Although the most rice brands are not properly controlled in quality management, its average level of grain quality is largely improved through the continuously increased diffusion of newly-developed high-quality rice cultivars since 1991. The rapid construction of rice processing complex(RPC) since 1992 also accelerates the production and distribution of brand rices. Especially, about half of distribution amounts are covered by brand rice commodities of the agricultural cooperative associations. The rice is mainly consumed by the type of cooked rice. The amounts of rice consumption for food processing is only below 4% of total rice consumption. The processed rice foods is mainly consumed as various processed cooked rices, rice cakes, and rice wines.

• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.1-9
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• 2019

BACKGROUND: Accurate and simple analytical method determining Fluxametamid residue was necessary in various food matrices. Additionally, fulfilment of the international guideline of Codex (Codex Alimentarius Commission CAC/GL 40) was required for the analytical method. In this study, we developed Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method to determine the Fluxametamid residue in foods. METHODS AND RESULTS: Fluxametamid was extracted with acetonitrile, partitioned and concentrated with dichloromethane. To remove the interferences, silica SPE cartridge was used before LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry) analysis with $C_{18}$ column. Five agricultural commodities (mandarin, potato, soybean, hulled rice, and red pepper) were used as a group representative to verify the method. The liner matrix-matched calibration curves were confirmed with coefficient of determination ($r^2$) greater than 0.99 at calibration range of 0.001-0.25 mg/kg. The limits of detection and quantification were 0.001 and 0.005 mg/kg, respectively. Mean average accuracies were shown to be 82.24-115.27%. The precision was also shown to be less than 10% for all five samples. CONCLUSION: The method investigated in this study was suitable to the Codex guideline for the residue analysis. Thus, this method can be useful for determining the residue in various food matrices as routine analysis.

• The Korean Journal of Pesticide Science
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• v.20 no.2
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• pp.93-103
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• 2016

A simultaneous analytical method was developed for the determination of isoxaflutole and metabolite (diketonitrile) in agricultural commodities. Samples were extracted with 0.1% acetic acid in water/acetonitrile (2/8, v/v) and partitioned with dichloromethane to remove the interference obtained from sample extracts, adjusting pH to 2 by 1 N hydrochloric acid. The analytes were quantified and confirmed via liquid chromatograph-tandem mass spectrometer (LC-MS/MS) in positive-ion mode using multiple reaction monitoring (MRM). Matrix matched calibration curves were linear over the calibration ranges ($0.02-2.0{\mu}g/mL$) for all the analytes into blank extract with $r^2$ > 0.997. For validation purposes, recovery studies were carried out at three different concentration levels (LOQ, 10LOQ, and 50LOQ) performing five replicates at each level. The recoveries were ranged between 72.9 to 107.3%, with relative standard deviations (RSDs) less than 10% for all analytes. All values were consistent with the criteria ranges requested in the Codex guideline (CAC/GL40, 2003). Furthermore, inter-laboratory study was conducted to validate the method. The proposed analytical method was accurate, effective, and sensitive for isoxaflutole and diketonitrile determination in agricultural commodities.

• Journal of Food Hygiene and Safety
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• v.31 no.3
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• pp.186-193
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• 2016

An analytical method was developed for the determination of oxathiapiprolin in agricultural commodities. Oxathiapiprolin is a new oomycide (fungicide of piperidinyl thiazole isoxazoline class) which controls downy mildew in cucurbits caused by Pseudoperonospora cubensis (oomycete plant pathogen). Agricultural commodities were extracted with acetonitrile and partitioned with dichloromethane to remove the interference, adjusting pH between 9 and 10 by 1 N sodium hydroxide. After purification by silica SPE cartridge to clean up the interference of organic compounds, they were finally quantified by HPLC-UVD (high performance liquid chromatograph ultraviolet detector) using a wavelength at 260 nm and confirmed by LC-MS (liquid chromatograph mass spectrometer) in electro-spray ionization positive ion mode. The standard calibration curve was linear with coefficients of determination ($r^2$) 1.00 over the calibration ranges (0.025-2.5 mg/L). Recoveries were ranged between 86.7 to 112.7%, with relative standard deviations less than 10% at three concentration levels (LOQ, 10LOQ, and 50LOQ) performing five replicates. The overall results were determined and estimated according to the CODEX guidelines (CAC/GL40). The proposed method for determination of oxathiapiprolin residues in agricultural commodities can be used as an official method.

• The Korean Journal of Pesticide Science
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• v.16 no.3
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• pp.202-208
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• 2012

A high-performance liquid chromatographic (HPLC) method was developed to determine residues of cyromazine, a triazine insecticide, in agricultural commodities. Cyromazine was extracted with 90% aqueous methanol from representative crops which comprised brown rice, oyster mushroom, oriental melon, watermelon, and Chinese cabbage. Following to evaporation of methanol in the extract, the aqueous concentrate was acidified to form the protonated cyromazine. Dichloromethane partition was then applied to remove nonpolar co-extractives in the aqueous phase. Strong cation-exchange chromatography using Dowex 50W-X4 resin was employed for final purification of the extract. Cyromazine was successfully separated on a Zorbax SB-Aq $C_{18}$ column showing high retention for polar compounds. Cyromazine was sensitively quantitated by ultraviolet absorption at 214 nm. Limit of quantitation (LOQ) of the method was 0.04 mg/kg irrespective of sample types. Each crops were fortified at 3 different concentrations of cyromazine for recovery test. Mean recoveries from samples fortified at LOQ~2.0 mg/kg in triplicate ranged 80.2~103.3% in five agricultural commodities. Relative standard deviations in recoveries were all less than 6%. A selected-ion monitoring LC/MS method with electrospray ionization in positive-ion mode was also provided to confirm the suspected residue. The proposed method was reproducible and sensitive enough to routinely determine and inspect the residue of cyromazine in agricultural commodities.