• Journal of the Chungcheong Mathematical Society
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• v.20 no.3
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• pp.231-243
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• 2007

In this paper, we study a Lotka-Volterra type simple food chain model. We investigate the positive coexistence of the steady states to the model and give some results for the extinction of species under certain assumptions which can be interpreted as Domino effect and Biological control. The methods of a decoupling operator and the fixed point index theory on a positive cone are used as well as the comparison argument. Numerical evidences for our results also are provided.

• The Korean Journal of Food And Nutrition
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• v.7 no.1
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• pp.36-44
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• 1994

In this paper, we surveyed the actual utilization condition of chain stores of franchise systems and the customers' consciousness on chain shops and non-chain restaurants. The survey was conducted on 459 people either living or working in Pusan area and aged more than 4th grade in elementary school without sex distinction. The data analyses were made by way of frequency, percentage, Spearman rank correlation and Chi-square using dBastat 1.0 package of PC. The results of the survey are as follows. The survey indicates that respondents have the most experience of visiting chicken, hamburger, and pizza chain shops. Although the survey on the degree of preference between chain shops and non-chain restaurants indicates that men prefer non-chain restaurants and women prefer chain shops, the results are not so significant to conclude that there is a preference regardless of sex (N. S.): By ages, students and young group prefer chain shops and the aged group prefer non-chain restaurants (p< 0.05). The survey indicates that chain shops are proffered because of sanitary, quality, taste of foods and are not proffered because of simple menu and expensiveness. The survey indicates that non-chain restaurants are preferred because of distinctive taste of each restaurant and comfotableness, and are not proffered because of unsanitary and unkindness.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.986-988
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• 2002

A plasmid expression vector of pEStxl encoding a mature form of the B chain of the Shiga toxin was constructed without a signal peptide under the control of an inducible n promoter. The encoded protein was purified to 90% by simple heat treatment, and then further purified to 95% by Phenyl-Sepharose and DEAE-Sepharose chromatographies, all in a single day. Accordingly, this expression system and heat treatment could facilitate the rapid purification of gram-scale amounts of the Shiga toxin B subunit from recombinant Escherichia coli cells.

• Communications of the Korean Mathematical Society
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• v.21 no.4
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• pp.701-717
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• 2006

The positive coexistence of a simple food chain model with ratio-dependent functional response and cross-diffusion is discussed. Especially, when a cross-diffusion is small enough, the existence of positive solutions of the system concerned can be expected. The extinction conditions for all three interacting species and for one or two of three species are studied. Moreover, when a cross-diffusion is sufficiently large, the extinction of prey species with cross-diffusion interaction to predator occurs. The method employed is the comparison argument for elliptic problem and fixed point theory in a positive cone on a Banach space.

• Korean Journal of Food Science and Technology
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• v.16 no.2
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• pp.251-253
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• 1984

A simple and modified method is developed to determine a lipase activity. A linear relationship exists between the color intensity and the free fatty acid liberated by enzyme action. The range of determination is from 0.05 to $1.5\;{\mu}moles$ of long chain fatty acid (oleic acid) and 0.2 to $2.0\;{\mu}moles$ of short chain fatty acid (caproic acid). The cumbersome procedure of the removal of the upper aqueous phase which was required in the previous copper soap extraction method was eliminated by the movement of solvent phase to upper phase in the respective biphasic system with a mixture solvent (chloroform: n-hexane:ethanol = 49:49:2) and copper reagent saturated with sodium chloride.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.704-708
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• 2015

For the analysis of multiple-reaction intermediates for long-chain dicarboxylic acid biotransformation, simple and reproducible methods of extraction and derivatization were developed on the basis of gas chromatography with flame ionization detector (GC-FID) instead of mass spectrometry. In the derivatization step, change of the ratio of pyridine to MSTFA from 1:3 to 9:1 resulted in higher peak intensity (p = 0.021) and reproducibility (0.6%CV) when analyzing 32 g/l ricinoleic acid (RA). Extraction of RA and ω-hydroxyundec-9-enoic acid with water containing 100 mM Tween 80 showed 90.4-99.9% relative extraction efficiency and 2-7%CV compared with those with hydrophobic ethyl acetate. In conclusion, reduction of the pyridine content and change of the extraction solvent to water with Tween 80 provided compatible derivatization and extraction methods to GC-FID-based analysis of longchain carboxylic acids.

• Journal of Environmental Health Sciences
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• v.41 no.2
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• pp.133-145
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• 2015

Objectives: Food safety has become one of the major public-concerning issues in Korea. In order to set guidelines to create manuals for the response to a food safety crisis by food industry, this paper classified food safety crises and suggested techniques to determine crisis level. Methods: This study clarified common terminologies and definitions including in food safety crises. It reviewed various food safety crises and described characteristics, types, and states of crises. Results: The results of this study suggested that a food safety crisis implied a situation in which hazards/risk spreading in the food supply chain was widely described, causing strong public concern followed by a socioeconomic impact, and therefore, requiring the implementation of a prompt and full response regarding the situation. In terms of seeking response plans, food safety crises might be classified according to the penalties resulting from violations of laws and regulations, causative substances, stages of the food supply chain, and first contact point for incidents. The crisis level for a food safety crisis could be classified according to its severity parameters. The guideline matrix was divided into four major stages: Blue/guarded, Yellow/elevated, Orange/high, and Red/severe. This study also suggested several methods for determining the crisis level, such as the simple judgement method, scoring methods using a check-list and a weighted check-list. Conclusion: The severity of related parameters might be of great importance in understanding a crisis and determining response options/challenges for crisis levels.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.9
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• pp.1241-1247
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• 2009

A large number of branded chicken products exist in Japan, and in some cases, the breed of chicken is an important factor used to attract consumer interest in the retail product. In order to establish a simple method for verifying such breed claims we applied the amplified fragment length polymorphism (AFLP) technique to nine chicken breeds (White Cornish, Red Cornish, White Plymouth Rock, New Hampshire, Rhode Island Red, Barred Plymouth Rock, Hinaidori, Tosajidori, Tsushimajidori) to search for molecular markers able to discriminate chicken breeds. Three breed-specific single nucleotide polymorphisms (SNP) were identified, one for each of Hinaidori, Tosajidori, or New Hampshire. A total of 219 individuals from the nine breeds were analyzed using a specific PCR test for each of these SNP. The PCR tests made it possible to discriminate between the breeds of chickens to identify products from these three breeds. This PCR method provides an efficient method for the routine analysis and verification of certified chicken products.

• The Plant Pathology Journal
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• v.38 no.3
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• pp.194-202
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• 2022

Erwinia amylovora and Erwinia pyrifoliae cause fire blight and black-shoot blight, respectively, in apples and pears. E. pyrifoliae is less pathogenic and has a narrower host range than that of E. amylovora. Fire blight and black-shoot blight exhibit similar symptoms, making it difficult to distinguish one bacterial disease from the other. Molecular tools that differentiate fire blight from black-shoot blight could guide in the implementation of appropriate management strategies to control both diseases. In this study, a primer set was developed to detect and distinguish E. amylovora from E. pyrifoliae by conventional polymerase chain reaction (PCR). The primers produced amplicons of different sizes that were specific to each bacterial species. PCR products from E. amylovora and E. pyrifoliae cells at concentrations of 10⁴ cfu/ml and 10⁷ cfu/ml, respectively, were amplified, which demonstrated sufficient primer detection sensitivity. This primer set provides a simple molecular tool to distinguish between two types of bacterial diseases with similar symptoms.

• Food Science and Preservation
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• v.15 no.1
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• pp.88-93
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• 2008

This paper focused on the detection of the genetically modified soybean (Glycine max L. MERRILL) samples to search for the speedy analysis methods. We have identified the PCR (polymerase chain reaction) assay with a newly developed technique called DHPLC (denaturing high performance liquid chromatography) to screen the GMO in soybean. The DHPLC is i1s ability to directly detection specific sequences of DNA by using column. With these characteristics. the DHPLC assay had the advantage of simplicity, rapidty could obtain result within 20 minutes. Whereas $15{\times}10^{-4}ng/{\mu}L$ concentration could be detected with the PCR analysis, $15{\times}10^{-5}ng/{\mu}L$ concentration could be detected with the DHPLC method. Therefore, DHPLC method was considered to be a simple, fast and sensitivity screening method rather than PCR analysis for GMO detection in soybean.