• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.239-243
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• 2005

The effect of pH and particle size on the dispersion stability of ultra-fine $BaTiO_3$ suspensions in aqueous medium have been investigated by means of zeta potential, sediment experiments, and powder properties (particle analysis, specific surface area) etc. Zeta potential as a function of pH for two particles of different size increases from -75 to +10 mV with decreasing pH from 8.5 to 1.4. The curve of zeta potential for small particle (150 nm) has slow slope than that of large particle (900nm), giving IEP (isoelectric point) value of pH=1.6 for small particle and pH=1.9 for large particle respectively, which means that it is more difficult to control zeta potential with pH fur small particle than large particle. The dispersion stability of $BaTiO_3$ particles in aqueous medium was found to be strongly related with the agglomeration of colloidal suspensions with time through the sedimentation behaviors of colloidal particles with time and pH value.

• Journal of the Korean Society of Food Culture
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• v.25 no.6
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• pp.788-794
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• 2010

Camellia sinensis L. (green tea) seed oils were prepared by roasting at $213^{\circ}C$ and pressing (RP), pressing (P), and nhexane extraction (H). The physico-chemical properties of the RP, P, and H samples, including fatty acid composition, color, and sensory characteristics were analyzed. RP, P and H samples were thermally oxidized at $180^{\circ}C$, and oxidative stability was determined by DPPH, CDA, and p-AV at 0, 20, 40, 60, and 80 min. Compared to the P and H samples, RP resulted in significantly higher thermal oxidative stability according to the DPPH, CDA, and p-AV results (p<0.05). The ratio of unsaturated fatty acids to saturated fatty acids among RP, P, and H samples were significantly different (p<0.05). The oleic acid and linoleic acid contents in green tea seed oils were 58 and 23%, respectively. Hunter's color value of lightness (L) for the RP, P, and H samples was not significant. Redness (a) of RP was $3.47{\pm}0.119$ and yellowness (b) of H was $60.10{\pm}2.483$, which were significantly different. Compared to RP samples, H and P samples had the highest color and off-odor values in the sensory evaluation. RP samples showed the highest taste value and were significant overall (p<0.05). The thermal stability of RP extraction was more stable than any other method. Camellia sinensis L. seed oil extracted by RP had better sensory characteristics than other edible oils, including soybean oil, grape seed oil, and extra virgin olive oil.

• YAKHAK HOEJI
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• v.20 no.1
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• pp.27-31
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• 1976

The stability of a newly introduced anthelmintic, mebendazole, in sweetened and aqueous suspension was tested by the accelerated temperature method and the effect of pH on the stability of mebendazole was studied. Mebendazole in aqueous and sweetened suspension was very stable at the pH range from 4 to 8.

• The Korean Journal of Food And Nutrition
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• v.18 no.1
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• pp.4-10
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• 2005

Periodate-oxidized soluble starch increased pH stability of Aspergillus awamori a-glucosidase. After incubation for two hours, the enzyme in the absence of oxidized soluble starch was stable in the range of pH 3-7 at 40℃, pH 3-6 at 50℃ and the enzyme in the presence of oxidized soluble starch was stable in the range of pH 3-9 at 40℃, pH 3-8 at 50℃. At 60℃, the enzyme was stable in pH 3-6 regardless of the presence or absence of IO₄-oxidized soluble starch, but when IO₄-oxidized soluble starch existed in pH 5-6, remained activity of the enzyme increased 20% more than when it didn't exist. The enzyme modified with IO₄-oxidized soluble starch remained 70% of activity in pH 9, but native enzyme didn't remain, showing the increase of stability due to modification. In thermal stability, modified enzyme remained 12% at 50℃ and 7% at 80℃. But native enzyme remained 8% at 50℃ and didn't remain at more than 70℃. The result of HPLC analysis revealed the subunit of the enzyme at under pH 2 or over pH 9 was separated or the enzyme was denatured and conjugated. Protein structure of native enzyme was denatured by acidic and basic pH but was stable in the presence of IO₄-oxidized soluble starch.

• Microbiology and Biotechnology Letters
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• v.6 no.1
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• pp.33-40
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• 1978

Immobilization of alkaline protease was investigated by absorbing the enzyme on adsorbents. Alkaline protease was adsorbed on silica gel selected as a carrier to immobilize the enzyme. In this study, properties of the immobilized enzyme were compared with those of the soluble enzyme. 1) The optimum pH (10.0) of the enzyme was not changed, but the activity was increased at alkaline pH by immobilization. 2) The optimum temperature of the immobilized enzyme was shifted from 50$^{\circ}C$ to 45$^{\circ}C$, while the temperature-activity Profile became broader than those of the soluble enzyme. 3) The pH stability of the immobilized enzyme was significantely increased at pH 4.0, althouth it did not change in the neutral and alkaline pH region. 4) The heat stability of the enzyme was enhanced in the temperature range of 55$^{\circ}C$∼65$^{\circ}C$ by the immobilization. 5) The immobilized enzyme retained 40％ of its original activity after repetitive use for 6 times. 6) The enzyme stability was greately improved for a prolonged storage at 4$^{\circ}C$.

• Korean journal of food and cookery science
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• v.4 no.2
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• pp.1-9
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• 1988

This study was carried out in order to study the foaming properties of mungbean protein. Mungbean protein isolate was tested for the purpose of finding out the effect of pH, addition of sucrose on foaming properties. The results were summarized as follows: 1. Foam expansion values were generally depen. dent on protein concentration to 3% protein suspension. From 1% to 3% suspension, foam expansion values increased. However over 3% suspension, the values decreased. In 1% mungbean protein suspension, the foam expansion value of suspension at pH 4.5 was greater than that of at pH9. In 3%, 5%, and 10% suspensiona the foam expansion values of suspension at pH 7 was the lowest. Foam expansion value significantly decreased by the addition of sucrose. 2. The foam stability appeared the greatest value as protein concentration increased. It appeared the greatest value at pH 4.5. When sucrose was added, the foam stability increased. The more sucrose was added, the better foam stability was.

• Journal of Pharmaceutical Investigation
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• v.39 no.5
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• pp.353-357
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• 2009

As a synthetic analog of the naturally occurring hormone somatostatin, octreotide has been commercially formulated in poly(lactide-co-glycolide) (PLGA) microspheres for the treatment of acromegaly. The purpose of this study was to evaluate stability of octreotide acetate in aqueous solutions at various pH values and PLGA films. Stability-indicating reversed-phase high-performance liquid chromatographic method was developed with good precision and accuracy, and it was applied to the stability studies. In aqueous solutions at pH 2.5-9.0, the degradation of octreotide followed approximately first order kinetics and the most favorable stability was found at pH 4. In PLGA films, the formation of acylated octreotides reached approximately 55% of the released octreotides. Various acylated octreotides was structurally identified by liquid chromatography-mass spectrometric analysis.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1843-1846
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• 2008

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.311-315
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• 1996

Thermal stability of aspartame was investigated as affected by the temperature and pH during heating. The thermal stability study of aspartame heated at $60-100^{\circ}C$ showed that aspartame was degraded more rapidly as the heating temperature increased. Activation energy for thermal degradation was 20.77 kcal/mol. The thermal degradation products, a diketopiperazine (DKP) and ${\alpha}$-aspartylphenylalanine (${\alpha}$-AP), were rapidly increased while the aspartame concentration decreased. The pH change of aspartame solution was rapidly decreased during initial three hours of heating and more significant at high temperature. In the pH range ()』 3-7, aspartame was the most unstable at pH 7 and stable at pH 4. The thermal degradation rate contants were 0.827 at pH 7, 0.286 at pH 6, 0.072 at pH 5 and 0.045 at pH 4 during initial heating at $100^{\circ}C$.

• Journal of Pharmaceutical Investigation
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• v.41 no.4
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• pp.233-238
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• 2011

DEET, N,N'-diethyl-m-toluamide, is the most commonly used mosquito repellent. However, it can easily permeate through skin leading to toxic effects. A recent study showed that the ortho analogue of DEET showed enhanced repellency with reduced permeation compared to the commercially used meta analogue. Thus, in order to understand the differences in properties and effectiveness among the m-, o- and p-analogues of DEET, an HPLC-UV method was developed for separately analyzing the three analogues. Moreover, stability profiles at temperatures ranging from $30^{\circ}C$ to $70^{\circ}C$ as well as pH ranging from pH 3 to pH 9 have been determined. All three analogues were stable with no degradation observed during the 5 day period. o-DEET therefore could be further developed into a safer and more effective mosquito repellent.