• Korean Journal of Environmental Agriculture
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• v.36 no.2
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• pp.97-105
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• 2017

BACKGROUND : Environmental stress has a major effect on the growth and yields of vegetables, and can significantly affect nutritionally important phytochemicals, causing large economic losses. METHODS AND RESULTS : The present study was aimed at exploring the effects of water stress on the carotenoid and proline contents in kale leaves to understand drought tolerance of kale plants. Kale was randomly divided into two groups at 57 days after sowing (DAS). One of the groups was well-watered (WW) and the other was water stressed (WS). Harvesting of kale leaves was started one day after treatment (58 DAS) and continued for 10 days (~67 DAS). We investigated the status of plant growth (leaf number, length, width, fresh weight) of kale throughout the study. Carotenoid (lutein, ${\alpha}-carotene$, zeaxanthin, ${\beta}-carotene$) and proline contents were analyzed by high-performance liquid chromatography (HPLC). Our results showed that the total carotenoid contents ranged from 926.0 to 1,212.0 mg/kg dry wt. (at 3 and 2 days, respectively) in WW treatment and 887.8 to 1,157.4 mg/kg dry wt. (at 10 and 4 days, respectively) in WS treatment. The ratio of individual carotenoid to the total carotenoid contents of kale leaves was 51.4 for lutein, 4.44 for zeaxanthin, 2.76 for ${\alpha}-carotene$, and 41.4% for ${\beta}-carotene$. Total carotenoid contents showed a significant reduction from 7 days (1,037.2 mg/kg dry wt.) to 10 days (887.8 mg/kg dry wt.) in WS treatment. The lutein content did not show a significant difference in WW between 7 and 10 days after treatment but showed a significant difference in WS treatment. The ${\alpha}-carotene$ content showed no significant difference between the treatments. However, zeaxanthin content was higher during 4-10 days and ${\beta}-carotene$ content was lower during 6-10 days in WS than in WW on each harvest day. In WW, the proline content showed no significant difference, but in WS, the proline content started to increase at 7 days and almost doubled in 10 days. CONCLUSION : The marked increase in zeaxanthin and proline contents in kale leaves indicated that the two phytochemicals are associated with drought tolerance in the plant.

• Journal of Food Hygiene and Safety
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• v.27 no.1
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• pp.37-41
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• 2012

The current standard for testing tetrodotoxin (TTX) in foodstuffs is the mouse bioassay (MBA) in Korea as in many other countries. However, this test suffers from potential ethical concerns over the use of live animals. In addition, the mouse bioassay does not test for a specific toxin thus a sample resulting in mouse incapacitation would need further confirmatory testing to determine the exact source toxin (e.g., TTX, STX, brevotoxin, etc.). Furthermore, though the time of death is proportional to toxicity in this assay, the dynamic range for this proportional relationship is small thus many samples must be diluted and new mice be injected to yield a result that falls within the quantitative dynamic range. Therefore, in recent years, there have been many efforts in this field to develop alternative assays. High performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) has been emerged as one of the most promising options. A LC-MS-MS method involves solid-phase extraction (SPE) and followed by analysis using an electrospray in the positive ionization mode and multiple reactions monitoring (MRM). To adopt LC-MS-MS method as alternative standard for testing TTX, we performed a validation study for the quantification of TTX in puffer fish. This LC-MS-MS method showed good sensitivity as limits of detection (LOD) of $0.03{\sim}0.08{\mu}g/g$ and limits of quantification (LOQ) of $0.10{\sim}0.25{\mu}g/g$. The linearity ($r^2$) of tetrodotoxin were 0.9986~0.9997, the recovery were 80.9~103.0% and the relative standard deviations (RSD) were 4.3~13.0%. The correlation coefficient between the mouse bioassay and LC/MS/MS method was higher than 0.95.

• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.389-395
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• 2017

A simultaneous determination of 5 phenolic acids (gallic acid, chlorogenic acid, caffeic acid, pcoumaric acid, trans ferulic acid) and 9 flavonoids (procyanidin b1, aspalathin, rutin, vitexin, hyperoside, isoquercitrin, luteolin, quercetin, chrysoeriol) in rooibos tea has been carried out by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). A validated analysis method in this study was applied to rooibos aqueous infusions. Rooibos tea is an antioxidant-rich tea which has anti-cancer, anti-aging, anti-inflammatory, anti-diabetic effect. Extraction yield of phenolics depends on steeping time and temperature of water. Tea infusions were prepared by placing 1 g of tea leaves or 1 tea bag in 100 mL of boiled water, and then at 3, 6 and 30 minutes intervals the infused teas were taken to carry out the analysis of phenolic contents. Another tea infusion was conducted with cold water ($25-30^{\circ}C$) for 30 minuntes. As a result, the total amount of phenolics was highest in rooibos tea steeped with hot water for 30 minutes, followed by 6 minutes, 3 minutes and cold water 30minutes and the result has statistical significance.

• Korean Journal of Food Science and Technology
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• v.43 no.3
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• pp.277-281
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• 2011

A rapid and very sensitive high-performance liquid chromatography/atmospheric-pressure chemical-ionization mass spectrometry method to detect ethylenethiourea (ETU) fungicide residues in fruits was developed. Methylene chloride was used as the surface extraction solvent for the target component. Recovery rates improved when cysteine hydrochloride and sodium carbonate were added to product prior to fortification. The limits of detection and quantification were approximately 0.006 and 0.02 mg/kg, respectively, from mandarin oranges. Recoveries from mandarin oranges, oranges, bananas, and pears, spiked in the range of 0.05-0.5 mg/kg, averaged 80-100%. The proposed method was used to monitor the presence of ETU in commercial fruits purchased from different markets in Seoul, Korea. ETU was found in four orange peels and in three mandarin orange peel samples. The highest ETU residue levels were $73.6{\mu}g/kg$ and $29.8{\mu}g/kg$.

• Korean Journal of Food Science and Technology
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• v.44 no.2
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• pp.196-201
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• 2012

Microorganisms, having the lower decarboxylase activity, among the isolated strains from $cheonggukjang$ and rice-straw in this study were selected by using biogenic amine (BA) media. The selected strains were identified as $Bacillus$ $subtilis$ HH12, $B.$ $subtilis$ HR254, and $Paenibacillus$ $barcinonensis$ KR97, by using 16S rRNA analysis. PCR analysis showed that the histidine decarboxylase ($hdc$) gene was absent in the HH12, HR254, and KR97 strains. However, PCR analysis showed that the tyrosine decarboxylase ($tdc$) gene was present in the HH12, HR254, and KR97 strains. Quantitative analysis of the selected strains by using high-performance liquid chromatography showed that histamine was absent in the HH12, HR254, and KR97 strains. However, these 3 strains showed tyramine concentrations of 6.09, 3.68, and 6.30 mg/L, respectively. These strains produced lower concentrations of amines (approximately 7.9, 0, and 9.3% amines in the HH12, HR254, and KR97 strains, respectively) than the $B.$ $subtilis$ MC138 strain, which showed the higher protease activity.

• Korean Journal of Food Science and Technology
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• v.41 no.2
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• pp.141-145
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• 2009

Cheongyukjang, a Banga food, is a heavy soy-soup prepared by boiling cheonggukjang, sea foods, and meats. Soybeans roasted at 140$^{\circ}C$ for 21.0 min and 220$^{\circ}C$ for 6.0 min, respectively, were used for cheonggukjang preparation. Distributions of isoflavones in raw soybeans, roasted soybeans, cheonggukjang, and cheongyukjang were analyzed by high performance liquid chromatography. The total isoflavones in roasted soybeans, cheonggukjang and cheongyukjang were about 79-80, 56-65, and 47-50% of those in raw soybeans, respectively. Roasting caused significant increases in acetyl derivatives and ${\beta}$-glucoside isoflavones, and significant decreases in malonyl derivatives (p < 0.05). The major isoflavones in cheonggukjang and cheongyukjang were ${\beta}$-glucosides. Succinyl-${\beta}$-daidzin and succinyl-${\beta}$-genistin, which are recognized as new metabolites of isoflavones, were not detected in raw and roasted soybeans. Peak areas of succinyl-${\beta}$-genistin were higher than thse of succinyl-${\beta}$-daidzin, in both cheongyukjang and cheonggukjang.

• Analytical Science and Technology
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• v.18 no.3
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• pp.250-256
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• 2005

A selective method of high performance liquid chromatography with UV detector has been applied to determine 4 tetracycline antibiotics in the animal food, simultaneously. The targets were chlortetracycline (CTC), doxycycline (DC), oxytetracycline (OTC), and tetracycline (TC) that are used routinely in veterinary medicine for prevention and control of disease. Food samples were beef, pork, chicken, milk, whole egg, flatfish (Limanda yokohamae), jacopever (Sebastes hubbsi), seabream (Chrysophrys major), eel (Anguilla japonica) and lobster (Hommarus americanus). After extracting food samples with 20% trichloroacetic acid and McIlvaine buffer, they were purified by a $C_18$ SPE cartridge with 0.01M methanolic oxalic acid solution. The concentrated residue was re-dissolved in methanol, filtered, cleaned up and analyzed on a $C_18$ column. The mobile phase was a mixture of 0.01M oxalic acid and acetonitrile with a gradient ratio from 85:15 to 60:40. The UV wavelength was 365 nm. The overall recoveries were ranged from 71% to 98% and the limit of detections were 0.022 for CTC, 0.012 for DC and OTC and 0.009 mg/kg for TC at signal/noise > 3, respectively. As results, CTC, DC and TC were not detected in all selected food samples, however, OTC was detected in meat and fishes. The determined level of OTC was 0.04 ppm for pork, 0.17 ppm for flatfish and 0.05 and 0.08 ppm for jacopever, that were within the Maximum Residue Limits (MRLs) in the food.

• Analytical Science and Technology
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• v.29 no.5
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• pp.234-241
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• 2016

The approach presented in this article refers to the bioanalytical method validation for the detection and quantitative determination of arsenic species including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) in dog plasma by high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP/MS). The arsenic species were separated using an agilent As speciation column by a mobile phase of 2 mM sodium phosphate monobasic, 0.2 mM ethylenediaminetetraacetic acid disodium salt dehydrate, 10 mM sodium acetate, 3 mM sodium nitrate and 1 % ethyl alcohol at pH 11 (adjusted with 1M NaOH). The method validation experiment was obtained selectivity, linearity, accuracy, precision, matrix effect, recovery, system suitability, dilution integrity and various stabilities. All calibration curves showed good linearity (R²>0.999) within test ranges. The lower limit of quantitation (LLOQ) was 5 ng/mL for As(III), As(V) and DMA, and 20 ng/mL for MMA. The system suitability and dilution values were within 6.5 % and 7.7 %. Subsequently, the developed and validated HPLC-ICP/MS method was also successfully applied to determine the arsenic speciation in dog plasma samples, and the recoveries for the spiked samples were in the range of 91.5–102.2 %. Therefore, this method could be applied to the evaluation of arsenic exposure, health effect assessment and other bio-monitoring studies in biological samples.

• Journal of Food Hygiene and Safety
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• v.22 no.1
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• pp.23-28
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• 2007

The residue depletion of streptomycin was investigated in the olive flounder (Paralichthys olivaceus), rockfish (Sebastes schlegeli), and red sea bream (Pagrus major) after consecutive three days treatment with dipping water at a dose of 20 g/ton water. Fishes were sampled for muscle on 1st, 2nd, 3rd, 4th, and 5th day after treatment. Streptomycin concentrations were determined by high performance liquid chromatography with tandem mass spectrometry. The recovery rates of streptomycin in muscle samples ranged from 87.2 to 102.3% and from 80.4 to 94.1% for the concentration of 0.05 mg/kg and 0.1 mg/kg, respectively. Streptomycin concentrations detected on the 1st day after treatment were 0.066, 0.058, and 0.073 mg/kg in muscles of olive flounder, rockfish, and red sea bream, respectively. At day 2, residue concentrations of all samples were believed to decrease to lower than 0.05 mg/kg, the detection limit. From results of the present study, a withdrawal period of streptomycin is proposed on 3 days after consecutive three days treatment with dipping administration at a dose of 20 g/ton water to avoid the presence of excessive residues of the edible muscles of olive flounder, rockfish, and red sea bream. The present study showed that residue concentrations of streptomycin decreased to below 0.05 mg/kg after treatment 2nd day.

• Journal of Food Hygiene and Safety
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• v.33 no.5
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• pp.354-360
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• 2018

This study presents a method validation for extraction and quantitative analysis of trichothecene mycotoxins in nuts based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach for extraction and enhanced matrix removal (EMR)-lipid-disperive-SPE (d-SPE) cleanup method, with detection and quantification by high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in positive- and negative-ion modes. Linearity, precision, and accuracy were validated for LC-MS/MS methods. Results obtained with LC-MS/MS were linear, with correlation coefficient ($R^2$) of 0.998. Limits of detection and quantification for mycotoxins were $0.41-3.57{\mu}g/kg$ and $1.23-10.82{\mu}g/kg$, respectively. Intra- and inter-day precisions (RSD, %) were 0.40-8.44% and 1.93-12.46%, respectively. Results indicated to be rapidly and accurately identifying trichothecene mycotoxins and may be used as a suitable safety management method for nuts and nuts related commodities.