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Studies on the Standardization of pH Measurement System (pH 측정 시스템의 표준화에 관한 연구)

  • Lee, Hwa Shim;Kim, Myung Soo;Kim, Jin Bok;Oh, Sang Hyup
    • Journal of the Korean Chemical Society
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    • v.42 no.4
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    • pp.432-442
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    • 1998
  • Since the definition of pH, $pH=-Ioga_H$ is based on a single ion activity, pH values can not be determined with measurement itself, but require an approximation method. They are derived from EMF measurement of a liquid junction free cell using hydrogen and Ag/AgCl electrodes. Primary standard materials with certified pH values can be obtained with this approximation method. Standard buffer solutions are used to calibrate pH meters. Thus the accuracy of the pH values of standard buffer solutions limits the reliability of measured pH values can be obtained with this approximation method. Standard buffer solution are used to calibrate pH meters. Thus the accuracy of the pH values of standard buffer solutions limits the reliability of measured pH values of sample solutions. To certify the pH values, we have established the system for the primary standard measurement and certified the pH of buffer solutions in the range of 1.6∼12.5 pH unit within uncertainty of ${\pm}0.005$ pH unit.

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Enhancement of Geldanamycin Production by pH Shock in Batch Culture of Streptomyces hygroscopicus subsp. duamyceticus

  • Song, Jae-Yang;Kim, Yoon-Jung;Hong, Young-Soo;Chang, Yong-Keun
    • Journal of Microbiology and Biotechnology
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    • v.18 no.5
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    • pp.897-900
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    • 2008
  • Various sequences of pH change were applied in a batch bioreactor to investigate pH shock effects on geldanamycin production by Streptomyces hygroscopicus subsp. duamyceticus JCM4427. In the control culture where the pH was not controlled, the maximum geldanamycin concentration was 414 mg/l. With the pHS1 mode of pH shock, that is, an abrupt pH change from pH 6.5 to pH 5.0 and then being maintained at around pH 5.0 afterward, 768 mg/l of geldanamycin was produced. With pHS2, in which the pH was changed sequentially from pH 6.7 to pH 5.0 and then back to pH 6.0, 429 mg/l of geldanamycin was produced. With pHS3 having a sequential pH change from pH 6.0 to pH 4.0 and then back to pH 6.5 followed by the third pH shock to pH 5.5, no geldanamycin production was observed. Considering that the productivity with pHS1 was about two-fold of that of the control culture with no pH control, we concluded that a more sophisticated manipulation of pH would further promote geldanamycin production.

Changes in Chlorophyll Contents of Leaves and pH of the Extracted Solutions from the Leaves of 7 Tree Species by pH Level (7개(個) 수종(樹種)의 잎이 pH수준별(水準別) 처리(處理)에 따른 엽록소(葉綠素) 함량(含量) 및 침출액(浸出液) pH변화(變化))

  • Woo, Jong Ho;Ahn, In Suk;Park, Young Goo
    • Journal of Korean Society of Forest Science
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    • v.87 no.2
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    • pp.145-152
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    • 1998
  • We conducted this study as a fundamental study on the response of various tree species against acid rain. The tree species used for this study were Zelkova serrata, Robinia pseudoacacia, Quercus acutissima, Prunus serrulata, Ginkgo biloba, Pinus koraiensis and Pinus densiflora. The leaves were examined for the pH changes by treatment time and the chlorophyll content into various pH solution in vitro. The results obtained were as follows ; 1. When the leaves were immersed in the solution of various pH(pH 3.0-pH 6.0) levels, the pH were changed to species specific pH ranges as pH 5.0~pH 5.5 of Z. serrata, pH 5.5~pH 6.0 of R. pseudoacacia, pH 4.5~pH 5.0 of Q. acutissima, pH 5.5~pH 6.0 of P. serrulata, pH 3.5~pH 4.5 of G. biloba, pH 3.5~pH 4.5 of P. koraiensis until 48 hours. However, in case of P. densiflora, it was difficult to find specific pH range of the species. Z. serrata, R. pseudoacacia and P. serrulata showed a little pH increasing by pH 2.0 solution treatment, while other species showed no change by the solution. 2. The amount of chlorophyll contents in Z. serrata, R. pseudoacacia and P. serrulata were decreased after immersing in the pH 2.0 solution. Chlorophyll content was almost constant in other pH levels. Other species showed almost constant chlorophyll contents in various pH levels and treatment time.

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The Study on Emulsifying and Foaming Properties of Buckwheat Protein Isolate (분리 메밀 단백질의 유화 및 기포특성에 관한 연구)

  • 손경희;최희선
    • Korean journal of food and cookery science
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    • v.9 no.1
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    • pp.43-51
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    • 1993
  • Buckwheat protein isolate was tested for the effects of pH, addition of sodium chloride and heat treatment on solubility, emulsion capacities, emulsion stability, surface hydrophobicity, foam capacities and foam stability. The solubility of buckwheat protein isolate was affected by pH and showed the lowest value at pH 4.5, the isoelectric point of buckwheat protein isolate. The solubility significantly as the pH value reached closer to either ends of the pH, i.e., pH 1.0 and 11.0. The effects of NaCl concentration on solubility were as follows; at pH 2.0, the solubility significantly decreased when NaCl was added; at pH 4.5, it increased above 0.6 M; at pH 7.0 it increased; and at pH 9.0 it decreased. The solubility increased above $80^{\circ}C$, at all pH ranges. The emulsion capacity was the lowest at pH 4.5. It significantly increased as the pH approached higher acidic or alkalic regions. At pH 2.0, when NaCl was added, the emulsion capacity decreased, but it increased at pH 4.5 and showed the maximum value at pH 7.0 and 9.0 with 0.6 M and 0.8 M NaCl concentrations. Upon heating, the emulsion capacity decreased at acidic pH's but was maximised at pH 7.0 and 9.0 on $60^{\circ}C$ heat treatment. The emulsion stability was the lowest at pH 4.5 but increased with heat treatment. At acidic pH, the emulsion stability increased with the increase in NaCl concentration but decreased at pH 7.0 and 9.0. Generally, at other pH ranges, the emulsion stability was decreased with increased heating temperature. The surface hydrophobicity showed the highest value at pH 2.0 and the lowest value at pH 11.0. As NaCl concentrationed, the surface hydrophobicity decreased at acidic pH. The NaCl concentration had no significant effects on surface hydrophobicity at pH 7.0, 9.0 except for the highest value observed at 0.8 M and 0.4 M. At all pH ranges, the surface hydrophobicity was increased, when the temperature increased. The foam capacity decreased, with increased in pH value. At acidic pH, the foam capacity was decreased with the increased in NaCl concentration. The highest value was observed upon adding 0.2 M or 0.4 M NaCl at pH 7.0 and 9.0. Heat treatments of $60^{\circ}C$ and $40^{\circ}C$ showed the highest foam capacity values at pH 2.0 and 4.5, respectively. At pH 7.0 and 9.0, the foam capacity decreased with the increased in temperature. The foam stability was not significantly related to different pH values. The addition of 0.4 M NaCl at pH 2.0, 7.0 and 9.0 showed the highest stability and the addition of 1.0 M at pH 4.5 showed the lowest. The higher the heating temperature, the lower the foam stability at pH 2.0 and 9.0. However, the foam stability increased at pH 4.5 and 7.0 before reaching $80^{\circ}C$.

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Comparision of Blood Gas Analyser, pH Meter and pH Strip Methods in the Measurement of Pleural Fluid pH (흉수의 pH 측정에서 혈액가스분석기계, pH meter, pH Strip 방법의 비교)

  • Jee, Hyun-Suk;Park, Yong-Bum;Choi, Jae-Chol;Ahn, Chang-Hyuk;Yoo, Ji-Hoon;Kim, Jae-Yeol;Park, In-Won;Choi, Byoung-Whui
    • Tuberculosis and Respiratory Diseases
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    • v.48 no.5
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    • pp.773-780
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    • 2000
  • Background : pH measurement is an important test in assessing the etiology of pleurisy and in identifying complicated parapneumonic effusion. Although the blood gas analyzer is the gold standard method' for pleural pH measurement, pH meter & pH strip methods are also used for this purpose interchangably. However, the correlation among the pH data measured by the three different methods needs to be evaluated. In this study, we measured the pH of pleural fluid with the three different methods respectively and evaluated the correlation among the measured data. Methods : From August 1999 to March 2000, we measured the pleural fluid pH in 34 clinical samples with three methods-blood gas analyzer, pH meter, and pH strip. In the blood gas analyzer and pH meter methods, the temperature of pleural fluid was maintained around $0^{\circ}C$ in air-tight condition before analysis and measurement was performed within 30 minutes after collection. As for the pH strip method, the pleural fluid pH was checked in the ward immediately after tapping and in the clinical laboratory of our hospital. This part is unclear. Results : The causes of pleural effusion were tuberculosis pleurisy in 16 cases, malignant pleural effusion 5 cases, parapneumonic effusion 9 cases, empyema 3 cases, and congestive heart failure 1 case. The pH of pleural fluid (mean$\pm$SD) was 7.34$\pm$0.12 with blood gas analyser, 7.52$\pm$0.25 with pH meter, 7.37$\pm$0.16 with pH strip of immediate measurement and 6.93$\pm$0.201 with pH strip of delayed measurement. The pH measured by delayed pH strip measurement was lower than those of other methods (p<0.05). The correlation of the results between the blood gas analyzer and pH meter(p=0.002, r=0.518) and the blood gas analyzer and pH strip of immediate measurement(p<0.001, r=0.607). Conclusion : In the determination of pH of pleural fluid, pH strip method could be a simple and reliable method under immediate measurement conditions after pleural fluid tapping.

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Kinetics of pH Changes during Thermal Degradation of MSG under Model System (Model System 하에서 MSG 열분해 중 pH 변화의 속도론적 연구)

  • Cha, Bo-Sook;Han, Min-Soo;Kim, Woo-Jung
    • Korean Journal of Food Science and Technology
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    • v.24 no.3
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    • pp.232-235
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    • 1992
  • Effect of temperature and initial pH were studied on the pH change of MSG solution during heating. The heating temperature and initial pH of 2% MSG solution were in the range of $100{\sim}120^{\circ}C$ and $pH\;2{\sim}9$, respectively. The results showed that the pH of MSG solution was more rapidly decreased as the temperature increased and the initial pH decreased due to pyroglutamic acid formation from MSG thermal degradation. A linear relationship was obtained between pH decreased and logarithmic value of heating time and the decreasing rate constant of pH were calculated from the slope. The pH decreased$({\Delta}pH)$ after 3 hrs of heating was 1.2 at the initial pH 4 and $120^{\circ}C$ and 0.33 at pH 5 and $120^{\circ}C$ while little pH change measured at the range of $pH\;6{\sim}9$. Activation energy calculated for pH decrease during heating was 11.77 and 22.26 kcal/mole at pH 4 and pH 5, respectively.

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Influences of Extraction pH on the Functionality of Soybean Protein Isolate (추출 pH가 분리대두단백질의 기능성에 미치는 영향)

  • Bae, Song-Hwan;Rhee, Chul
    • Korean Journal of Food Science and Technology
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    • v.30 no.3
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    • pp.557-561
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    • 1998
  • This study was conducted to investigate the functionality of soybean protein isolates extracted in acidic range (pH 2.0 and 3.0), neutral range (pH 7.0) and alkaline range (pH 10.0 and 12.0). The protein content of soybean protein isolates extracted at pH 3.0 was maximum (93.31%), but that of pH 7.0 was minimum (73.93%). The extraction yield of soybean protein isolates extracted at pH 3.0 was minimum (0.36%), but that of pH 12.0 was maximum (47.54%). The functionality (solubility, water absorption, oil absorption, foam capacity, foam stability, emulsion capacity and gelation) of soybean protein isolates was significantly influenced by pH of extraction medium. The soybean protein isolates extracted at pH 2.0 and 3.0 were more soluble at acidic ranges and those of pH 3.0 and 7.0 were more soluble at neutral ranges, but those of pH 2.0, 3.0, 7.0, 10.0 and 12.0 were more soluble at alkaline ranges than other ranges. The soybean protein isolates extracted at pH 2.0 and pH 12.0 gave greater water absorption, oil absorption and foam capacity than those extracted at pH 3.0, pH 7.0 and pH 10.0. And the emulsion capacity of soybean protein isolates was increased by the increase of extraction pH.

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Effect of pH on Continuous Hydrogen Fermentation (연속반응실험에서 수소생성에 대한 pH 영향)

  • Lee, Young-Joon
    • Journal of Environmental Health Sciences
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    • v.30 no.2
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    • pp.149-153
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    • 2004
  • The influences of pH on hydrogen production were also investigated over the pH range from 4.1 to 8.0 at HRT 10 hours. The hydrogen content for the produced gas was changed from 41 to 71% with corresponding pHs throughout this experiment. The produced hydrogen/carbon dioxide ratio was not vary significantly up to 6.0, then steepenly increased with increases in the pH. The maximal hydrogen yield was found to be 3.16 $\ell$/g sucrose at pH 5.0. Acetate production yield increased with increased pH, but butyrate production yield decreased with increased pH. Biomass yield increased with increased pH.

Problem Analysis of the Experiments Illustrating pH Effects on Enzyme Activities in High School Science Textbooks - Focus on Starch-Iodine Reaction - (고등학교 과학 교과서에서 "pH가 효소의 작용에 미치는 영향" 실험의 문제점 분석 -녹말과 요오드 반응을 중심으로-)

  • Ji, Jae-Hwa;Jeong, Dae-Hong
    • Journal of The Korean Association For Science Education
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    • v.29 no.8
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    • pp.923-933
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    • 2009
  • In this study, analysis was carried out on science experiment in high school textbooks, illustrating 'the effect of pH on enzyme activity.' Five of the total 16 science textbooks introduced in this experiment, and the experimental conditions therein were analyzed. Textbook analysis revealed that pH of below 3 was used for 'acidic condition' and that of over 11 was used for 'basic' condition. Using the experimental conditions described in the textbooks, review experiments were performed. Buffering effect with the addition of saliva was found in the pH region around 7 when buffer solution was not used to control pH as was in the textbooks. The enzyme activity experiments were performed controlling pH from pH 2 to 13 with buffer. The color of the sample was blue from pH 2 to 4, and then disappeared from pH 5 to 8, reflecting that starch was digested owing to enzyme activity. In pH 9 light blue color appeared, indicating de-activation of enzyme under this basic condition. However, the blue color of the sample became lighter at pH 10 and disappeared from pH 11, which was different from the expected behavior anticipating dark blue color due to de-activation of enzyme under strong basic condition. These results can wrongly influence students to interpret that enzyme can be activated in this pH condition. So, we analyzed the reason for the color of the sample turning light blue in pH 10 and disappeared from pH 11. The analysis resulted that ${I_3}^-$ and/or ${I_5}^-$ subunits of polyiodides within the starch helix in starch-iodine complex, showing blue, decreases above pH 10 due to disproportionation to HOI, ${IO_3}^-$, and $I^-$ by the reaction with $OH^-$.

Studies on the Removal of Phytate from Korean Perilla (Perilla ocimoides, L.) Protein (들깨종실단백질 중의 phytate 제거에 관한 연구)

  • Park, Jin-Hee;Yang, Cha-Bum
    • Korean Journal of Food Science and Technology
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    • v.22 no.3
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    • pp.343-349
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    • 1990
  • The solubility of protein and phytate was measured at various pH's in distilled water and at various concentrations of NaCl, $CaCl_2\;and\;Na_2SO_3$ solutions, and then optimum condition for producing low phytate protein isolate from perilla flour was investigated. The protein solubility in water showed minimum at pH 4.0 and increased at pH higher or lower than 4.0, while phytate solubility was highest at pH 5.0 and decreased at pH higher or lower than 5.0. In NaCl solution, protein solubility was lowest between pH 3.0-4.0, while phytate solubility was high between pH 2.0-5.0 and abruptly decreased above PH 6.0. In $Na_2SO_3$ solution, protein solubility was lowest between pH 2.0-3.0 and phytate solubility showed maximum values between pH $5.0{\sim}6.0$, and it's solubility was low in 3% salt concentration at all pH ranges. In $CaCl_2$ solution, protein solubility in 3% salt concentration was relatively low at all pH ranges, and phytate solubility showed highest values between pH $2.0{\sim}3.0$ and abruptly decreased (1.0%) above pH 4.0. In order to make low phytate protein isolate, defatted perilla flour protein was extracted at pH9.0 and precipitated at pH 4.0 in 3% NaCl solution. The yield of low phytate protein isolate was 61.4% of total protein. This protein was found to contain 0.02% phytate by weight.

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