• Korean journal of food and cookery science
• /
• v.9 no.1
• /
• pp.43-51
• /
• 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 $80^{\circ}C$.

• Journal of the Korean Applied Science and Technology
• /
• v.26 no.2
• /
• pp.191-198
• /
• 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.

• Microbiology and Biotechnology Letters
• /
• v.6 no.1
• /
• pp.33-40
• /
• 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
• /
• v.11 no.4
• /
• pp.720-723
• /
• 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.

• Korean Journal of Poultry Science
• /
• v.17 no.2
• /
• pp.127-133
• /
• 1990

This study was undertaken to find out the effect of heating time and temperature, pH and NaCl concentration on the heat stability of egg albumen gel during heat treatment. With the transient decrease at 110-$130^{\circ}C$, hardness of heat-set albumen gel was increased as the heating temperature increased. The cohesiveness showed similar trend as well. The lightness was decreased while the yellowness was increased as the heating time and temperature increased. Heat-set albumen gel showed maximum hardness at pH 4.5-5.0 and pH 9.0 High heat treatment($120^{\circ}C$, 30min) showed higher hardness at alkaline range compared to low heat treatment($96^{\circ}C$, 30min.). Color of the albumen gel was relatively dark at acidic range and bright at alkaline range. High heat treatment caused darker albumen gel at alkaline range and brighter albumen gel at acidic range. The addition of NaCl increased hardness and cohesiveness of the albumen gel and improved the lightness after high heat treatment regardless of NaCl concentration.

• Korean Journal of Food Science and Technology
• /
• v.28 no.2
• /
• pp.311-315
• /
• 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 $100^{\circ}C$.

• Preventive Nutrition and Food Science
• /
• v.1 no.1
• /
• pp.53-58
• /
• 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.

• Proceedings of the SCSK Conference
• /
• 2003.09b
• /
• pp.60-72
• /
• 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.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.11
• /
• pp.1335-1341
• /
• 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.

• Journal of Life Science
• /
• v.23 no.5
• /
• pp.669-675
• /
• 2013

The stability of monascus pigment produced by Monascus sp. MK2 was investigated according to light, pH, temperature, organic acid, synthetic antioxidant, and natural substance. The light stability was increased (sun light < fluorescent lamp < ultraviolet rays < dark condition) when storing the monascus pigments. Although the monascus pigments were stable in the range of pH 3.0, the degradation rate of pigment was increased at pH 11.0. The stability of monascus pigment gradually decreased as temperature increased. In addition, pigment stability was increased by adding the synthetic antioxidant and natural substance.