• Korean Journal of Soil Science and Fertilizer
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• v.29 no.4
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• pp.347-352
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• 1996

These experiments were conducted to monitor the change in $NO_3{^-}-N$ in a plastic film house where $NO_3{^-}-N$ have been accumulated in the soil of high level (about 370 mg/kg) The objective of this study was to obtain the information needed to establish the N Fertilizer recommendation based on the available N content in the soil for vegetable cultivation. The cultivated crops were chinese cabbage in the spring, lettuce in the summer, and chinese cabbage in the autumn. The crops were cultivated with and without N application. The concentration of $NO_3{^-}-N$ in the soil was analysed before and after the cultivation of each crop. When $NO_3{^-}-N$ in the soil is as high as 370 mg/kg. even without N application, the yield of the first season crop, cabbage in the spring was 175 ton/ha and that of second season crop, lettuce in the summer was 53 ton/ha. These yields were comparable with those obtained under the application of N fertilizer: meaning that no N application would be needed for those crops when $NO_3{^-}-N$ in the soil is as high as 370 mg/kg. The yield of third crop, cabbage in the autumn was higher under N application than that under no N application by 62%. The fate of $NO_3{^-}-N$ in the soil differed along with the crop sequence. In the first crop, 14.5% was absorbed by crop, 25.4% remained in the soil and 60.1% was unaccounted for. In the second season, 25.3% was absorbed by crop, 51.8% remained in the soil and 22.9% was unaccounted for. In the third crop, 62.8% was absorbed by crop, 19.4% remained in the soil and 16.8% was unaccounted for.

• Journal of Bio-Environment Control
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• v.32 no.2
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• pp.97-105
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• 2023

Concentration of nitrogen, one of the major elements, and ratio of two nitrogen forms (NH₄⁺ and NO₃^-) in the nutrient solution affect the quality and food safety of fresh vegetable produce. This study was conducted to find an appropriate strength and NH₄⁺:NO₃^- ratio of a nutrient solution for growth and development of a Romaine lettuce (Lactuca sativa L. var. longiflora) 'Caesar Green', a representative leafy vegetable, grown in a home hydroponic system. In the first experiment, plants were grown using three types of nutrient solution: A commercial nutrient solution (Peters) and two strengths (GNU1 and GNU2) of a multipurpose nutrient solution (GNU solution) developed in a Gyeongsang National University lab. Plants grown with the GNU1 and GNU2 had greater shoot length, leaf length and width, and biomass yield than Peters. On the other hand, the root hairs of plants grown with Peters were short and dark in color. Tissue NH₄⁺ content in the Peters was higher than that of the GNU1 and GNU2. The higher contents of NH₄⁺ in this solution may have caused ammonium toxicity. In the second experiment, eight treatment solutions, combining GNU1 and GNU2 solutions with four ratios of NO₃^- :NH₄⁺ named as 1, 2, 3 and 4 were used. Both experiments showed more growth in the GNU2 group, which had a relatively low ionic strength of the nutrient solution. The growth of Romaine lettuce showed the greatest fresh weight along with low tissue NO₃^- content in the GNU2-2. This was more advantageous in terms of food safety in that it suppressed the accumulation of surplus NO₃^- in tissues due to the low ionic trength of the GNU2 subgroup. In addition, this is preferable in that it can reduce the absolute amount of the input of inorganic nutrients to the nutrient solution.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.9
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• pp.1325-1332
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• 2015

Lettuce (Lactuca sativa) is an important dietary leafy vegetable that is primarily consumed as a fresh or salad material. It has a number of cultural varieties with green and/or red color. Carotenoids and anthocyanins are known to be responsible for these two colors, respectively. In this study, carotenoid and anthocyanin contents were determined to evaluate the stability of these functional pigments during storage at home. Analyses were carried out at the beginning, 3, 6, 9, and 12 days after harvest. In the course of storage at room temperature, total carotenoid levels rapidly decreased, and the decrease was found to be greatest during the first 3 days. Meanwhile, carotenoid level slightly changed within the first 9 days at $4^{\circ}C$ after harvest. This result suggests that carotenoids in green lettuce are more stable when refrigerated than at room temperature. Meanwhile, total anthocyanin content in red lettuce did not significantly decrease during storage at room temperature and $4^{\circ}C$, which indicates that anthocyanins have higher stability during storage compared with carotenoids in green lettuce. Anthocyanin extract exhibited higher antioxidant activity than carotenoid extract based on 2,2'-azino-bis(3-ethylbenzothazoline-6-sulfonic acid) (ABTS) radical scavenging assay. Antioxidant activity of anthocyanin extract may also be estimated directly by the presence of another potent hydrophilic antioxidant compound, which is ascorbic acid in this extract. In addition, anthocyanin extract showed about a 5-fold higher amount of anthocyanins than carotenoids in the carotenoid extract. The high correlation between carotenoid content with ABTS radical scavenging activity indicates that ABTS assay is more suitable than 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay for detecting antioxidant capacity of carotenoid extract from lettuce.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.11
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• pp.1796-1800
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• 2014

Trienzyme digestion (AOAC Official Method 2004.05) procedure using protease, ${\alpha}$-amylase, and chicken pancreas conjugase was evaluated to determine its usefulness in the microbiological quantitation of total folate in foods. Folate values obtained by alkali hydrolysis (Korean Food Standards Codex) were compared to those obtained by the trienzyme method for four certified reference materials (CRM) representing diverse matrixes. Trienzyme treatment increased measurable folate from most CRM compared to levels found after alkali hydrolysis. The largest increases were observed with CRM 487 (pig liver, 5.8-fold) and CRM 121 (whole meal flour, 3.1-fold) after trienzyme digestion. Using trienzyme digestion method, total folate contents of raw and blanched edible plants were determined. Eleutherococcus senticosus ($146.9{\mu}g/100g$) showed the highest total folate content, followed by Aster glehni F. Schmidt ($142.8{\mu}g/100g$) and Ledebouriella seseloides H. Wolff ($140.4{\mu}g/100g$) on a wet weight basis. Blanching of samples resulted in an insignificant decrease in folate content for five samples and 11~63% reduction for nine samples. Our finding suggests that trienzyme digestion method is accurate for the determination of food folate in leafy vegetables.

• Korean Journal of Food Science and Technology
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• v.39 no.2
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• pp.114-121
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• 2007

The purpose of this study was to investigate 253 kinds of pesticide residues in 58 commercial dried agricultural products in Seoul. The determinations of the pesticide residues were performed using multiresidue methods and were carried out by a gas chromatography-nitrogen phosphorus detector (GC-NPD), an electron capture detector ($GC-{\mu}ECD$), a mass spectrometry detector (GC-MSD) and high performance liquid chromatography-ultraviolet detector (HPLC-UV), and a fluorescence detector (HPLC-FLD). The pesticide residue detection rate in the commercial dried agricultural products was 24.1% (14 of 58 samples). Twelve pesticide residues without maximum residue limits (MRLs) were detected. In the vegetable groups, the frequency of pesticide residues was found to be in the increasing order of dried fruiting vegetables > dried leafy vegetables > dried stalk and stem vegetables. The pesticides used on dried red pepper in the dried fruiting vegetables were varied (7 kinds) and numerous (4 of 8 samples). The pesticide types detected in the commercial dried agricultural products were in the order of pyrethroid > organochloride > organophosphorus and insecticide > fungicide > herbicide ${\cdot}$ nematicide. The primary pyrethroid pesticide detected was cypermethrin. According to the producing areas of products, large numbers of pesticide residues were found in the order of Korea, China, North Korea, USA, and Vietnam.

• Korean Journal of Microbiology
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• v.47 no.2
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• pp.117-123
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• 2011

The purpose of this study was to evaluate and compare different elution and concentration methods for optimization of human rotavirus (HRV) detection method using real-time RT-PCR and cell culture techniques. The leafy vegetable samples (lettuce, Chinese cabbage) were artificially inoculated with HRV. Viruses were extracted from the vegetables by two different elution buffers, buffer A (100 mM Tris-HCl, 50 mM glycine, 3% beef extract, pH 9.5) and buffer B (250 mM Threonine, 300 mM NaCl, pH 9.5), and the extracted viruses were concentrated by filtration and PEG precipitation sequentially. To determine infectivity of the viruses, the viruses recovered from the samples were infected to the MA-104 cells, and integrated cell culture real-time RT-PCR was performed at 1, 48, 72, 96, 120, 144, 168 h post-infection (p.i.). The elution buffer A was more efficient in extracting the virus from the produce samples tested than the buffer B, 29.54% and 18.32% of recoveries, respectively. The sensitivity of real-time RT-PCR method was markedly improved when the virus was concentrated by the filtration method. When the viruses were eluted and concentrated by buffer A and filtration, respectively, the average recovery rate was approximately 51.89%. When the viruses recovered from samples were infected to MA-104 cell, infectious HRV was detected within 48 h p.i. by ICC/real-time RT-PCR, whereas cytopathic effects were not observed until 72 h p.i. The optimized detection method evaluated in this study could be useful for rapid and reliable detection of HRV in fresh produce products and applied for detection of other food-borne viruses.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.7
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• pp.980-989
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• 2016

In the present study, we compared and investigated the nutritional compositions of Amaranthus cruentus and Amaranthus hypochondriacus baby-leaves cultivated in Korea. Baby-leaves of two amaranthes consisted of more than 92% moisture, and A. cruentus contained a higher amount of moisture than A. hypochondriacus. Meanwhile, A. hypochondriacus contained higher levels of crude ash, crude protein, crude lipid, carbohydrates, and dietary fiber than A. cruentus. The major free sugars of the two amaranth baby-leaves were fructose and glucose. Fructose content of A. hypochondriacus was higher than that of A. cruentus, and glucose content of A. cruentus was higher than that of A. hypochondriacus. Acetic acid, malic acid, and fumaric acid were detected in two amaranth leaves, but succinic acid was not detected. Two amaranth leaves contained 17 amino acids except for methionine, proline, and tyrosine, and leaves contained the highest glutamic acid contents. In addition, A. cruentus and A. hypochondriacus leaves contained high contents of taurine and ${\gamma}$-aminobutyric acid and showed various biological activities. The major mineral and fatty acid of the two amaranth leaves were potassium and linolenic acid (C18:3), respectively. The ${\beta}$-carotene contents of A. cruentus and A. hypochondriacus leaves were $478.72{\mu}g/100g$ and $474.12{\mu}g/100g$, respectively. In vitamin B complex, $B_2$, $B_3$, and $B_5$ were detected in the two amaranth leaves whereas vitamins $B_1$, $B_6$, and $B_{12}$ were not detected. A. hypochondriacus contained higher amounts of vitamin C and E than those of A. cruentus. Overall, amaranth leaves contained high amounts of nutritional components. Therefore, amaranth leaves are expected to be useful for the development of a functional food. Moreover, these results will provide fundamental data for advancing sitological value, breeding new cultivars, and promoting leafy vegetable usage.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.872-878
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• 2014

This study aimed to enhance storage and freshness of strawberry fruits and foliage vegetables by spray treatment with Chlorella vulgaris as a bio-fertilizer. The tested strain, C. vulgaris CHK0008, was isolated from an organically cultivated rice paddy and identified as C. vulgaris by its morphology and 18S rDNA and 23S rDNA sequence homology. We successfully cultured C. vulgaris CHK0008 in BG11 modified medium (BG11MM) and adjusted $2.15{\times}10^6cell/mL$ C. vulgaris CHK0008 to one OD value by measuring the optical density at 680 nm using a UV-vis spectrophotometer. The soluble solid content of 'Seolhyang' and 'Yukbo' strawberry fruits treated by spray application with C. vulgaris CHK0008 was enhanced by 22.2% and 11.5% respectively, compared to untreated controls. Additionally, the decay rates of treated 'Seolhyang' and 'Yukbo' strawberry fruits decreased 63.8% and 74.4% respectively, compared to untreated control. Surface color changes and chlorosis of leaves in leaf vegetables such as lettuce, kale, red ornamental kale, white ornamental kale and beet were observed in samples treated with water spray for 10 days after cold storage. However, the decay rate of leafy vegetables treated with foliar application of 25% C. vulgaris CHK0008 liquid culture was significantly decreased compared to that of the untreated control during storage at $4^{\circ}C$.

• Horticultural Science & Technology
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• v.34 no.1
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• pp.172-182
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• 2016

This study was aimed to determine the changes in vitamin $B_5$ and $B_6$ contents compared to fresh materials after parboiling treatment of the main vegetables consumed in Korea. The specificity of accuracy and precision for vitamin $B_5$ and $B_6$ analysis method were validated using high-performance liquid chromatography (HPLC). The recovery rate of standard reference material (SRM) was excellent, and all analysis was under the control line based on the quality control chart for vitamin $B_5$ and $B_6$. The Z-score for vitamin $B_6$ in food analysis performance assessment scheme (FAPAS) proficiency test was -1.0, confirming reliability of analytical performance. The vitamin $B_5$ and $B_6$ contents in a total of 39 fresh materials and parboiled samples were analyzed. The contents of vitamin $B_5$ and $B_6$ ranged from 0.000 to 2.462 and from 0.000 to $0.127mg{\cdot}100g^{-1}$, respectively. The highest contents of vitamin $B_5$ and $B_6$ were $2.462mg{\cdot}100g^{-1}$ in fresh fatsia shoots (stem vegetables), and $0.127mg{\cdot}100g^{-1}$ in fresh spinach beet (leafy vegetables), respectively. Moreover, the vitamin $B_5$ and $B_6$ contents for parboiling treatment in most vegetables were reduced or not detected. In particular, the contents of vitamin $B_5$ in parboiled fatsia shoots and vitamin $B_6$ in parboiled yellow potato and spinach beet were decreased 20- and 4-fold compared with fresh material, respectively. These results can be used as important basic data for utilization and processing of various vegetable crops, information for dietary life, management of school meals, and national health for Koreans.

• Research in Plant Disease
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• v.26 no.4
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• pp.272-278
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• 2020

The severe lettuce damage caused by Paratylenchus projectus was first reported in 2019 in Korea. To find high-value rotation crops for the control of P. projectus, nine vegetables, Brassica juncea (leaf mustard), B. rapa subsp. nipposinica (kyona), B. oleracea var. italica (broccoli), B. rapa subsp. chinensis (bok choy), B. oleracea var. viridis (kale), B. oleracea var. gongylodes (kohlrabi), Cichorium endivia (endive), C. intybus (chicory), Ipomoea aquatica (morning glory) were planted in d-10-cm clay pots in greenhouse. The growth of vegetables was compared between inoculated with 3,000 P. projectus per 100 ㎤ of soil and non-inoculated. Treatments were replicated 10 times. After 100 days, the reduction of fresh top weight was 30.4% in C. intybus, 35.1% in I. aquatica, 36.9% in B. oleracea var. acephala, 40.5% in C. endivia, 42.1% in B. rapa, 47.5% in B. rapa subsp. nipposinica, 50.4% in B. oleracea var. gonglodes, 56.3% in B. oleracea var. italica, and 66.0% in B. juncea. Nematode multiplication rates (Pf/Pi) were lower in I. aquatica (0.64) and C. endivia (1.1), but higher in B. oleracea var. gongylodes (2.54). Considering these results, I. aquatica is suitable for the rotation crop with lettuce until better rotation crops developed.