• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.112-116
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• 2018

In this study, the mixing characteristics of water glass and additives (Si, alkali metal), which are one of the main raw materials of silicate based binder used in the production of molds during casting process, were examined. Molecular structures of water glass, additives and mixtures were analyzed FT-IR and viscosity measurements and their correlation were compared. The addition of Si source to the water glass accelerated the Si networking in the material and increased the viscosity. When the alkali metal was added, the viscosity of the water glass decreased by suppressing the Si networking of the water glass. Viscosities of the water glass and lithium silicate (LS) mixtures increased when the content of LS was less than 20 wt% and gradually decreased when the content was more than 20 wt%. By adding KOH to the water glass, the viscosity could be lowered and it could be used effectively to mix with colloidal silica (CS) or potassium methyl siliconate (PMS).

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.593-597
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• 1995

To measure theological properties of the starch dough, an Extrusion Capillary Viscometer(ECV) cell was self-made and attached to Instron machine(Model 1140). Apparent viscosities of corn and waxy corn starch doughs were measured and their gelatinization degrees were determined by enzymatic analysis. The effects of heating temperature on the viscosity of starch dough with $36{\sim}52%$ moisture contents were examined in terms of Arrhenius equation. The activation emergy(Ea) of the dough viscosity from the effect of heating temperatures changed from negative(-) to positive(+), as the moisture content increased from 44% to 48% in the corn starch dough and from 44% to 44% in the waxy corn starch dough.

• Korean Journal of Food Science and Technology
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• v.32 no.4
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• pp.806-813
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• 2000

Attempts were made to evaluate possibilities of adding water soluble chitosan to milk for improving functionality of milk, and physico-chemical and sensory properties of chitosan added milk were studied. pH and acidity of milk with ethyl alcohol washed chitosan were close to those of control. Color and consistency of chitosan added milk were better with chitosan of lower molecular weight than with high molecular weight. Chitosan of high molecular weight resulted in increased consistency and browning of milk. Milk with less than 1.0% chitosan could be sterilized at $73^{\circ}C$ for 15 sec. with minimum protein coagulation and increase of consistency. Low molecular weight chitosan$(MW\;0.2{\sim}3\;kDa)$ accelerated the growth of Bifidobacterium bifidum, showing 10 times more cell population after 32 hrs incubation. Sensory tests showed that adding chitosan to the regular city milk resulted in significant difference in color and chemical off-flavor(p<0.05). When chitosan was added to coffee milk, there was no significant difference in sensory quality from control. The storage test showed that pH, acidity, consistency and color of coffee milk with 0.5% chitosan did not change markedly during 30 days storage at 0 and $5^{\circ}C$, but changed rapidly after 16days storage at $10^{\circ}C$. Bacterial counts increased when storage temperature was high, and the growth of bacteria was delayed in coffee milk with chitosan.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.638-643
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• 1999

In this study we prepared 5 types of nutritional beverage base samples containing various ratios of soy protein isolate (SPI) and sodium caseinate as protein source. The rheological properties of each sample were measured and the results were as followes; Samples changed their rheological properties with the ratio of SPI. Samples represented newtonian property with low ratio of SPI, pseudoplastic property with the increment of SPI, and bingham pseudoplastic property with higher increment of SPI (80% as protein source). In this result we conjectured that the more was the SPI, the more was the formation of progel during heat treatment, which could be the reason of the rheological changes. In the test of the relationship between temperature and apparent viscosity, apparent viscosity of samples decreased along with the increment of temperature. In observing the relationship between time and apparent viscosity, we found sample, containing high ratio of SPI (80%), represented thixotropic property clearly with the hysteresis loop.

• Korean Journal of Food Science and Technology
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• v.37 no.4
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• pp.597-602
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• 2005

Quality factors of emulsified ginseng drink were determined during storage at various temperatures, and its shelf-life was predicted based on changes in emulsion stability, acidify, viscosity, and yellowness. Viscosity was highly dependent on storage temperature. Emulsion stability changed rapidly during early storage period (1st step), then slowly thereafter (2nd step). $Q_{10}$ values of emulsion stability were 2.50 and 1.38 for 1st and 2nd steps, respectively. Viscosity, acidity, and yellowness showed $Q_{10}$ values of 3.45, 1.77, and 1.99, respectively. Although $Q_{10}$ value of 2 has been generally used to predict shelf stability of food materials, our results suggest adopting same $Q_{10}$ value to predict shelf stability of emulsified ginseng drink is not appropriate.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.28-33
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• 1999

Introducing boric acid to the polyviny alcohol(PVA) solutions has a profound effect on the rheological properties through crosslinking between hydroxyl groups of PVA. This study investigates the effect of boric acid on the rheological properties of polyvinyl alcohol(PVA)/dimethyl sulfoxide(DMSO)/water systems in the absence of cations. The viscosity of PVA/ DMSO/water systems containing 1 wt.% boric acid was decreased with increasing water content. PVA/DMSO systems containing 1 wt.% boric acid exhibited rheological properties similar to elastic gels by forming crosslinked structures. On the other hand, PVA/water systems containing 1 wt.% boric acid exhibited rheological properties typical of viscous materials. In-corporation of boric acid into PVA/DMSO system caused a notable change in the viscosity of the system, whereas boric acid had little effect on the viscosity of PVA/water system. PVA/DMSO/boric acid system gave the greatest storage modulus among the PVA solution systems. Increasing water level in the mixed solvent of DMSO and water diminished the storage modulus of the systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.241-250
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• 1990

Characteristic relaxation time and characteristic diffusion time of viscoelastic fluids are determined experimentally by measuring the zero-shear-rate viscosity by falling ball viscometer and the infinite-shear-rate viscosity by capillary tube viscometer. Fluids used in experiments are aqueous solutions of polyacrylamide Separan AP-273 and the polymer concentrations range from 300 to 2000 wppm. A newly designed laser beam and timer system is employed to overcome the difficulty in measuring terminal velocities of the low concentration solutions. Ball removal device is prepared to remove the dropped ball from the bottom of cylinder without disturbing the testing fluid. In order to measure the zero-shear-rate viscosity, densities of hollow aluminium balls are adjusted very close to the densities of testing fluids. Characteristic diffusion time, which is ball viscometer. However, terminal velocity of a needle by falling ball viscometer is not affected by the time interval of dropping needles and characteristic diffusion time is not measured with a dropping needle. Powell-Eyring model predicts the highest values of the characteristic relaxation times among models used for heat transfer experimental works for a given polymer solution. As degradation of a polymer solution continues, the zero-shear-rate viscosity decreases more seriously than the infinite-shear-rate viscosity. Characteristic relaxation times of polymer solutions decreases as degradation continues.

• Korean journal of food and cookery science
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• v.20 no.4
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• pp.396-402
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• 2004

The aim of this study was to examine the effect of rice protein on the network structure of the Jeung-Pyun. The major component of Jeung-Pyun rice protein was extracted, the change of rice protein during the Jeung-Pyun fermentation was assessed, and the effect on the viscosity and volume of adding protease to Jeung-Pyun was investigated. In addition, the result of adding protein to rice starch on the viscosity and volume of Jeung-Pyun was that the rice protein mediated the volume and expansion ability. The results were as follows. In rice and dough of Jeung-Pyun, the SDS soluble protein content was higher than that of wheat flour and no change was detected in the amount of extracted protein with the fermentation time. However, in the FPLC pattern, low molecular weight peaks were decreased with the fermentation time, which indicates the increase in the ratio of high molecular weight substances. In contrast, the addition of protease substantially decreased, the viscosity and volume of Jeung-Pyun, whereas the viscosity and volume were increased by adding protein to rice starch in order to reconstitute Jeung-Pyun. This suggested that rice protein in Jeung-Pyun had a mediating effect on both the volume and the formation of the texture.

• Korean Journal of Food Science and Technology
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• v.33 no.1
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• pp.157-160
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• 2001

RS yields and swelling powers of cross-linked RS 4 starches and effects of RS 4 starches on the pasting profiles of RS 4 added wheat starch were measured using RVA. RS yields by AOAC method were different among RS 4 starches and RS levels were higher in low swelling RS 4 starches than moderate swelling RS 4 starches. Swelling power was different with botanical source of starch and preparing procedure of RS 4 starches. The pasting curves of RS 4 added wheat starches showed increasing initial pasting temperature and lower viscosity but the patterns were similar to those of wheat starch. The pasting viscosity pattern of RS 4 added wheat starches was related with swelling power of RS 4 starch.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2002.05a
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• pp.105-106
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• 2002