• 한국식품조리과학회지
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• 제9권1호
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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 $80^{\circ}C$.

• 한국응용과학기술학회지
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• 제26권2호
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• pp.191-198
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• 2009

We have tested the stability of paeoniflorin, a new cosmetic ingredient, extracted from the roots of Paeoniae lactiflora. The stability of aqueous paeoniflorin solution at pH 3, 5 and 7 varied by adding buffer solution was tested at $0^{\circ}C,\;25^{\circ}C,\;40^{\circ}C,\;and\;65^{\circ}C$. The test was performed with or without UV light. The solution of paeoniflorin was stable at pH 3.0, however, the recovery rate of paeoniflorin was 40% at pH 7.0. The stability of paeoniflorin solution was decreased as the pH of paeoniflorin solution was increased by pH 7.0. The effect of storage temperature of paeoniflorin solution shows that the stability of paeoniflorin solution was decreased as the temperature was increased. The stability of paeoniflorin was rather good under UV light than the condition given above $40^{\circ}C$. The stability of paeoniflorin in W/O emulsions shows similar pattern to that of aqueous solution.

• 한국미생물·생명공학회지
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• 제6권1호
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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$^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.720-723
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• 2001

The effect of long-term storage on garlic antibacterial activity was investigated. A concentration of 5% or more garlic was found to be necessary to completely inhibit Eschrichia coli growth in tryptic soy broth. This value is substantially higher than the minimum inhibitory concentration of 1% for E. coli reported previously. pH-modified garlic extract was stored at different temperatures to investigate the impact of storage conditions (i.e., temperature, pH, period of storage) on the stability of the antibacterial activity of the garlic extract used against E. coli B34. The antibacterial effectiveness of the garlic extract against E. coli remained stable when both the storage temperature and the pH of the extract were kept low. When the garlic extract was stored at $40^{\circ}C and above, most or all of the garlic antibacterial activity disappeared after a 24-h storage period, regardless of the storage pH. The antibacterial activity was weakened when the pH of the garlic extract was adjusted to 8, and at low temperatures.

• 한국가금학회지
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• 제17권2호
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• pp.127-133
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• 1990

가열온도와 시간, pH 및 NaCl 농도가 난백겔의 열안정성에 미치는 영향을 검토하기 위하여 가열처리 후 난백겔의 특성을 검토하였으며 그 결과는 다음과 같다. 난백을 90~$170^{\circ}C$까지 온도와 시간별 가열처리 한 결과. 110~$130^{\circ}C$ 영역에서 경도가 떨어졌으나 온도가 높아짐에 따라서 급격히 증가하였다. 응집성의 경우는 12$0^{\circ}C$까지 감소한 후 $130^{\circ}C$에서 급격히 증가하였다. 명도는 온도가 높아질수록 시간이 길어질수록 낮아졌으며 황색도는 높아졌다. 난백의 경도는 pH 7을 중심으로 산성영역에서는 고온처리가 높았으며 알카리영역에서 밝았다. 고온처리의 경우가 저온처리에 비해 산성영역에서는 보다 밝았으며 알카리 영역에서는 보다 어두웠다. 염의 첨가에 의해 난백의 경도는 저온처리 시에는 큰 변화가 없었으나 고온처리시 다소 증가하였고 응고집성은 저온처리시 서서히 증가하였으며 고온처리시 0.5%까지 급격히 증가하였다. 색택은 고온고리시 명도가 증가하였고 황색도는 감소하였으며 농도별 차이는 크지 않았다.

• 한국식품과학회지
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• 제28권2호
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• pp.311-315
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• 1996

아스파탐을 가열할 때 온도 및 pH가 아스파탐의 열안정성에 미치는 영향을 조사하였다. 아스파탐 용액을 $60-100^{\circ}C$로 가열하였을 때 가열온도가 높아질수록 아스파탐의 분해속도가 빨라졌으며 이 때의 활성화 에너지는 20.77 Kcal/mole이었다 또한 열분해물질인 DKP와 ${\alpha}$-AP는 아스파탐의 열분해와 함깨 생성속도가 증가하였으며, 분해산물 증 DKP량이 ${\alpha}$-AP보다 현저하게 많이 생성되었다. 가열 중 pH의 변화는 $60{\sim}80^{\circ}C$에서는 10시간 가열동안 비교적 완만하게 감소하였고 $100^{\circ}C$에서는 초기 pH 4.52에서 3.92로 감소하였다가 그 후 다시 완만하게 감소하였다. 1%아스파탐 용액을 pH $3{\sim}7$의 범위로 조절하여 $100^{\circ}C$에서 가열하였을 때 pH $3.0^{\circ}C4.5$의 산성범위에서 안정하였고 PH7에서 불안정하였으며, 초기 1시간 가열 후 pH 7에서의 열분해 속도상수는 0.83으로 다른 pH의 열분해 속도상수의 값인 $0.045{\sim}0.286$에 비해 큰 차이를 보였다. 따라서 아스파탐은 pH 7과 고온에서 매우 불안정함을 보여 주었다.

• Preventive Nutrition and Food Science
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• 제1권1호
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• pp.53-58
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• 1996

The characterstics of the soy protein curd(eczyme-, HCI- and Ca-surd) were shown by scanning electron micrographs and gel electrophoreis. The emulsion stability of enzyme-curd showed high value in the range of pH 2~10and wide range of temperature(20~8$0^{\circ}C$). While at the isoelectric point(pH5.0), the emulsion stability of the HCI-and Ca-curd was decreased remarkably, and the emulsion stability of temperature was reduced quickly to the 60% and 40% at the 4$0^{\circ}C$. The foam stability of enzyme-curd was slightly higher than that HCI-and CA-curd in all ranges of pH and temperature. The feature of SEM of enzyme-cured produced degradation products faster than that of the HCI- and Ca-curd.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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• pp.60-72
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• 2003

To investigate the effect of cholesterol in liposome on the stability of incorporated retinol, the physico-chemical experiments for various amounts of cholesterol-containing liposomes were performed. Liposome with retinol containing cholesterol was prepared as multilamella vesicles(MLVs) by dehydration/rehydration method. The incorporation efficiency of retinol into liposome was maximized as 99.31 % at 50:50 (phosphatidylcholine/cholesterol) at pH 9. The stability of incorporated retinol at low storage temperature was enhanced with increasing cholesterol content than at high storage temperature. For example, incorporated retinol in liposome at glycine buffer(pH 9} was degraded slowly during storage at 4. The degradation of retinol in liposomes was slower at pH 9 than at pH 7. These results supported that cholesterol in liposome increased largely the stability of incorporated retinol.

• 대한전자공학회논문지
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• 제25권11호
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• pp.1335-1341
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• 1988

A pH-ISEFET microprobe for in vivo measurements has been fabricated by combining ISFET (SL-IIS) chip and capillary thin film reference electrode. A two-step TCE oxidation for the gate oxide layer and multilayer encapsulation using silicone rubber and epoxy were specially used for the improvement of the stability and temperature dependence of the ISFET's. The measured sensitivit, response time and temperature dependence of the pH-ISFET microprobes are 50 mV/pH, less than one second, and - 0.01 pH/$^{\circ}$ , respectively. By operating continuously more than 40 days, a long term stability of 0.016 pH/day is obtained. The result of pH monitoring of femoral arterial blood in a rabbit is fairly good agreement with the value of blood gas analysis.

• 생명과학회지
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• 제23권5호
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• pp.669-675
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• 2013

본 연구에서는 Monascus sp. MK2가 생산하는 홍국색소의 안정성에 대하여 조사한 결과에서 광 안정성에서는 암 조건>자외선>실내(형광)>태양광 조건 순서로 안정하였으며, 온도에 대한 안정성은 온도가 증가하고 저장시간에 길어짐에 따라 홍국색소의 감소율 또한 비례적으로 증가하였고, pH에 대한 안정성은 전체적인 pH 영역에서 비교적 안정하였으며, 유기산 첨가에 대한 홍국색소의 안정성은 높은 것으로 생각되며, 합성 항산화제와 천연물 추출물 첨가시에는 안정성이 증대되는 것으로 조사되었다.