• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.83-88
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• 2017

We introduced disposable amperometric immunosensors for the detection of Sildenafil and Vardenafil (SDF/VDF) based on screen printed carbon electrodes. The developed immunosensors were used as a non-competitive sandwich-type enzyme immunoassay with a horseradish peroxidase label. The sensors were constructed on screen printed carbon electrodes by the simple electrochemical deposition of a reduced graphene oxide and chitosan (ErGO-CS) composite. To evaluate the sensing chemistry and optimize the sensor characteristics, a series of electrochemical experiments were carried out including electrochemical impedance spectroscopy, cyclic voltammetry and amperometry. The sensors showed a linear response to SDF/VDF concentrations in a range from 100 pg/mL to 300 ng/mL. The lower detection limit was calculated to be 55 pg/mL, the sensitivity was calculated to be $1.02{\mu}Ang/mL/cm^2$, and the sensor performance exhibited good reproducibility with a relative standard deviation (RSD) of 7.1%. The proposed sensing chemistry strategy and the sensor format can be used as a simple, cost-effective, and feasible method for the in-field analysis of SDF/VDF in functional or health supplement food samples.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.9
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• pp.1198-1204
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• 2007

This study was carried out to find the optimal conditions for the extraction of the effective ingredients based on central composite by monitoring the extraction characteristics of each ingredient with a response surface methodology. The optimal condition for the effective component alliin was extract temperature of $60.86^{\circ}C$, extract time of 3.77 hr, and ethanol concentration of 50.68%, and that for allicin was $65.11^{\circ}C$, 2.79 hr, and 13.62%, respectively, with the maximum extraction of 16.72 mg%. The maximum value of extracted total phenolics was 16.72 mg%, the optimal condition for electron donating ability was $93.35^{\circ}C$, 3.22 hr and 10.38%. The optimal conditions for pH 1.2 and 3.0 nitrite-scavenging ability was extract temperature of $79.77^{\circ}C$ and $76.46^{\circ}C$, extract time of 3.22 hr and 3.31 hr, and the ethanol concentration of 10.38% and 1.12%, respectively. With this optimal condition, the obtained maximum values for nitrite-scavenging activities at pH 1.2 and 3.0 were 94.85% and 63.22%, respectively.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.51-57
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• 2023

Because of the global pollution caused by plastic disposal, demand for eco-friendly transformation in the packaging industry is increased. As part of that, the utilization of polylactic acid (PLA) as a food packaging material is increased. However, it is necessary to improve the crystallinity of PLA by adding nucleating agents or to improve the modulus by adding fillers because of the excessive brittleness of the PLA matrix. Thus, the cellulose nanofiber (CNF) was fabricated and dried to obtain a powder form and applied to the CNF/PLA nanocomposite. The effect of CNF on the morphological, thermal, rheological, and dynamic mechanical properties of the composite was analyzed. We can confirm the impregnated CNF particle in the PLA matrix through the field emission scanning electron microscope (FE-SEM). Differential scanning calorimetry (DSC) analysis showed that the crystallinity of not annealed CNF/PLA nanocomposite was increased approximately 2 and 4 times in the 1st and 2nd cycle, respectively, with the shift to lower temperature of cold crystallization temperature (T_cc) in the 2nd cycle. Moreover, the crystallinity of annealed CNF/PLA nanocomposite increased by 13.4%, and shifted T_cc was confirmed.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.50-58
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• 1995

These studies were carried out to develop a system for non -destructive and continuous measurement of fresh weight and to analyse the growth response of leaf lettuce under the different nutrient solution and light condition with this system. The developed measurement system was consisted of four load cells and a microcomputer. The output from the system was highly positive correlation with the plant fresh weight above the surface of the hydroponic solution. The top fresh weight of plant could be measured within the error $\pm$ 1.0g in the range of 0 - 2000g. The top fresh weight of leaf lettuce increased 44 times at 18th day after transferring to the nutrient solution, and the maximum growth rate was observed at 13th day after transferring. The growth rate was 10.7- 29.6% per day during 18 days. Optimum concentration of the nutrient solution for the growth of lettuce was 1.4 - 2.2 mS/cm of EC level. When the light condition was changed from dark to light, the fresh weight was temporarily decreased, but the fresh weight increased under the opposite condition. Top fresh weight of leaf lettuce in the darkness normally increased within 12 hours after darkness treatment, and then slowly increased until 78 hours under continuous dark condition. After that times, the fresh weight began to decrease.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.63-70
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• 1998

This study was carried out to investigate the interaction of selenate and sulfate ion in nutrient solution supplyed with selenate ion. At early growth stage, the growth of Mongolian wormwood was best at 3mM sulfate ion and 2mg/$\ell$Na$_2$SeO$_4$ treatment. As they were grown and matured, at the later growth stage, the effect of antagonism between selenate and sulfate ion on the growth of each plant decreased. At supplying with selenate ion in nutrient solution, the uptake of selenate by plant had negative correlation with sulfate ion concentration in nutrient solution. The higher sulfate ion concentration, the less selenium uptake. However, the effect of antagonistic interaction of selenate and sulfate ion on the selenium uptake increased with plant age. Whereas, the uptake of sulfate ion had positive correlation with sulfate ion concentration in nutrient solution at supplying with selenate ion in nutrient solution. The uptake of sulfate ion increased with increase of sulfate ion concentration in nutrient solution. The effect of this interaction with selenate and sulfate ion increased with growth and maturity of plant. However, at 3mM sulfate ion concentration in nutrient solution, sulfate ion concentration in plant tissue decreased markedly.

• Journal of the Korean Wood Science and Technology
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• v.49 no.4
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• pp.336-359
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• 2021

In this study, hybrid CLT research and development trends were analyzed to improve the low rolling shear strength of CLT, a large wooden panel used in high-rise wooden buildings. Through this, basic data that can be used in research and development directions for localization of CLT were prepared. As a way to improve the low rolling shear strength, the use of hardwood lamina, the change of the lamina arrangement angle, and the use of structural composite materials are mainly used. Rolling shear strength and shear modulus of hardwood lamina are more than twice as high as softwood lamina. It confirmed that hardwoods can be used and unused species can be used. Rolling shear strength 1.5 times, shear modulus 8.3 times, bending stiffness 4.1 times improved according to the change of the layer arrangement angle, and the CLT strength was confirmed by reducing the layer arrangement angle. Structural wood-based materials have been improved by up to 1.35 times MOR, 1.5 times MOE, and 1.59 times rolling shear strength when used as laminas. Block shear strength between the layer materials was also secured by 7.0 N/mm², which is the standard for block shear strength. Through the results of previous studies, it was confirmed that the strength performance was improved when a structural wood based materials having a flexural performance of MOE 7.0 GPa and MOR 40.0 MPa or more was used. This was determined based on the strength of layered materials in structural wood-based materials. The optimal method for improving rolling shear strength is judged to be the most advantageous application of structural wood based materials with strength values according to existing specifications. However, additional research is needed on the orientation of CLT lamina arrangement according to the fiber arrangement of structural wood-based materials, and the block shear strength between lamina materials.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.342-349
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• 2018

In this study, the physicochemical properties, emulsifying capacity, moisture content and cytotoxicity of the composite material produced by transesterification reactions of the olive oil (olive oil esters) were investigated for cosmetic applications. Olive oil esters with short (S) and long (L) reaction times were studied. From the TLC-image analysis, composition ratios of the olive oil esters S were found to be 5.2, 24.1, 46.4, and 21.9% for mono-, di-, tri-glyceride, and fatty acid ethyl ester, respectively. Those of the olive oil esters L were 4.1, 24.7, 40.6, and 28.8% for mono-, di-, tri-glyceride, and fatty acid ethyl ester, respectively. The iodine value, acid value, saponification value, unsaponified matter, refractive index, and specific gravity were determined and purity tests were also carried out and normalized to establish standards and testing methods for using olive oil esters in cosmetics. To evaluate their emulsifying capacities, the O/W emulsion was prepared without surfactants and the formation of the emulsified particles were confirmed. After 5 days of applying the olive oil esters to human skin, the skin moisture retention was improved by 13.1% from the initial state. For the evaluation of toxicity on human skin cells, the olive oil esters showed 90% or more of the cell viability at $0.2-200{\mu}g/mL$. These results suggested that olive oil esters can be applied as natural/non-toxic ingredients to cosmetics industries.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1031-1031
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• 2001

The mammary gland is made up of remarkably sensitive tissue, which has the capability of producing a large volume of secretion, milk, under normal or healthy conditions. When bacteria enter the gland and establish an infection (mastitis), inflammation is initiated accompanied by an influx of white cells from the blood stream, by altered secretory function, and changes in the volume and composition of secretion. Cell numbers in milk are closely associated with inflammation and udder health. These somatic cell counts (SCC) are accepted as the international standard measurement of milk quality in dairy and for mastitis diagnosis. NIR Spectra of unhomogenized composite milk samples from 14 cows (healthy and mastitic), 7days after parturition and during the next 30 days of lactation were measured. Different multivariate analysis techniques were used to diagnose the disease at very early stage and determine how the spectral properties of milk vary with its composition and animal health. PLS model for prediction of somatic cell count (SCC) based on NIR milk spectra was made. The best accuracy of determination for the 1100-2500nm range was found using smoothed absorbance data and 10 PLS factors. The standard error of prediction for independent validation set of samples was 0.382, correlation coefficient 0.854 and the variation coefficient 7.63%. It has been found that SCC determination by NIR milk spectra was indirect and based on the related changes in milk composition. From the spectral changes, we learned that when mastitis occurred, the most significant factors that simultaneously influenced milk spectra were alteration of milk proteins and changes in ionic concentration of milk. It was consistent with the results we obtained further when applied 2DCOS. Two-dimensional correlation analysis of NIR milk spectra was done to assess the changes in milk composition, which occur when somatic cell count (SCC) levels vary. The synchronous correlation map revealed that when SCC increases, protein levels increase while water and lactose levels decrease. Results from the analysis of the asynchronous plot indicated that changes in water and fat absorptions occur before other milk components. In addition, the technique was used to assess the changes in milk during a period when SCC levels do not vary appreciably. Results indicated that milk components are in equilibrium and no appreciable change in a given component was seen with respect to another. This was found in both healthy and mastitic animals. However, milk components were found to vary with SCC content regardless of the range considered. This important finding demonstrates that 2-D correlation analysis may be used to track even subtle changes in milk composition in individual cows. To find out the right threshold for SCC when used for mastitis diagnosis at cow level, classification of milk samples was performed using soft independent modeling of class analogy (SIMCA) and different spectral data pretreatment. Two levels of SCC - 200 000 cells/$m\ell$ and 300 000 cells/$m\ell$, respectively, were set up and compared as thresholds to discriminate between healthy and mastitic cows. The best detection accuracy was found with 200 000 cells/$m\ell$ as threshold for mastitis and smoothed absorbance data: - 98% of the milk samples in the calibration set and 87% of the samples in the independent test set were correctly classified. When the spectral information was studied it was found that the successful mastitis diagnosis was based on reviling the spectral changes related to the corresponding changes in milk composition. NIRS combined with different ways of spectral data ruining can provide faster and nondestructive alternative to current methods for mastitis diagnosis and a new inside into disease understanding at molecular level.

• Current Research on Agriculture and Life Sciences
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• v.29
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• pp.83-89
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• 2011

Various functional and useful components in Portulaca oleracea were extracted with ethanol and the optimum solvent conditions were set by monitoring of response surface methodology(RSM). A central composite design for optimization was applied to investigate the effects of the three independent variables of extraction temperature, ethanol concentration, and extraction time, on dependent variables including total phenolics, electron-donating ability, brown clolor and total flavonoids of Portulaca oleracea. The content of total phenol was essentially unaffected by extraction time or extraction temperature, but it was highly influenced by ethanol concentration. The maximum total phenol content was 31.70mg/mL obtained at 45.84% of ethanol concentration, $79.66^{\circ}C$, and after 2.67hr of extraction. Electron-donating ability (EDA) was affected by ethanol concentration and the maximum EDA was 74.67mg/mL at 52.95% ethanol concentration, $52.33^{\circ}C$ and 4.84hr of extration time. The browning color was rarely affected by extraction time but, it was highly influenced by ethanol concentration and extraction temperature. The maximum extent of browning color was obtained at 97.75% of ethanol concentraion, $65.88^{\circ}C$ and 2.93hr of extraction time. The content of total flavonoid was significantly influenced by extraction time, and the maximum total flavonoid level was 58.28mg/mL obtained at 96.62% ethanol concentration, $61.87^{\circ}C$ after 3.70hr of extraction. As a result, The optimal conditions for effective extraction were predicted as follows, 70.3% of ethanol concentration, $62.1^{\circ}C$ of extraction temperature and 3.3hr of extraction time.

• Food Science and Preservation
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• v.15 no.1
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• pp.58-65
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• 2008

The Acorn (Quercus acutissima CARRUTHERS), which contains a large quantity of tannin, should be developed as a processed food as the acorn is rich in natural antioxidants and other valuable components. Accordingly, acorn extraction conditions for polyphenol and gallic acid (both antioxidants) were investigated by response surface methodology. The content of polyphenols were determined under 16 different extraction conditions based upon a central composite design. The parameters varied over $30-70^{\circ}C$ of extraction temperature, 1-5 h of extraction time, and 5-25 mL/g of solvent ratio, Gallic acid extraction was optimal at $60-100^{\circ}C$ extraction temperature, 1-5 h of extraction time, and 5-25 mL/g of solvent ratio, Epicatechin content was highest at $56.77^{\circ}C$, 4.16 hand 22.38 mL/g. Catechin content was highest at $52.37^{\circ}C$, 2h and 23.59 mL/g. The maximum catechin content was $91.30{\mu}g/mL$. Epigallocatechin content was influenced by extraction temperature and time. The maximum epigallocatechin content was $1,066.56{\mu}g/mL$ at $61.42^{\circ}C$, 4.17h, and 9.25 mL/g. The maximum value of epicatechingallate content was $125.39{\mu}g/mL$ at $47.72^{\circ}C$, 3.04h, and 24.93mL/g. Epigallocatechingallate content was influenced principally by solvent ratio and the maximum content was $61.38{\mu}g/mL$ at $48.11^{\circ}C$, 2.96h, and 24.95mL/g. The total polyphenol content was maximal at $1,332.75{\mu}g/mL$, after extraction at $61.50^{\circ}C$, 4.24h, at 9.71mL/g. The higher the extraction temperature and the longer the extraction time, the greater the polyphenol content. Gallic acid content was highest, the maximal level was $30.51{\mu}g/mL$ after $65.84^{\circ}C$, 1.65h at 17.17 mL/g, and this was influenced principally by extraction time and solvent ratio.