• Korean Journal of Food Science and Technology
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• v.21 no.6
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• pp.742-748
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• 1989

Rheological properties of gelatinized millet starch dispersions were evaluated. Gelatinized nonwaxy and waxy millet starch dispersion were typical pseudoplastic fluids. At constant shear rate, gelatinized waxy millet starch dispersion showed higher shear stress than nonwaxy millet starch dispersion. Flow behaviours of gelatinized nonwaxy and waxy millet starch dispersion were well fitted to Herschel-Bulkley equation and flow behaviour index (n) and consistency index (K) were strongly concentration dependent. There was a linear relationship between concentration of gelatinized starch dispersion and square root of yield stress. The concentrations of gelatinized nonwaxy and waxy millet starch dispersion where yield stresses become zero were estimated as 2.19 and 1.69%, respectively. Pseudoplastic constant (m) approaches to a constant value in each type of millet starch when the concentration of gelatinized starch dispersion was increased. As the measuring temperatures increase, n value was increased, whereas, K value was decreased. The activation energies of gelatinized nonwaxy and waxy millet starch dispersion were 2.89 and 3.18kcal/mol, respectively.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.33-38
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• 2006

This study was performed to provide basic rheological data of dandelion root concentrates in order to predict their processing aptitude and usefulness as functional foods material. The hot water and 70% ethanol extracts of dandelion root were concentrated at 5, 20, and 50 Brix, and their static viscosity, dynamic viscosity, and Arrhenius plots were investigated. Almost all hot water concentrates showed the typical flow properties of a pseudoplastic fluid, but evaluation using the power law model indicated that the 70% ethanol concentrates showed a flow behavior close to a Newtonian fluid. The apparent viscosity of hot water and 70% ethanol concentrates decreased with increasing temperature. Yield stresses of hot water and 70% ethanol concentrates by Herschel-Bulkley model application were in the range of 0.026 - 1.368 Pa and 0.022 - 0.238 Pa, respectively. The effect of temperature and concentration on the apparent viscosity was examined by Arrhenius equation. The activation energies of hot water and 70% ethanol concentrates were in the range of $8.762-23.778{\times}10^3\;J/mol{\cdot}kg$ and $3.217-20.384{\times}10^3\;J/mol{\cdot}kg$ with increasing concentration, respectively. Storage (G') and loss (G") moduli were generally increased with increasing frequency. For the 70% ethanol concentrates, G" predominated over G' at all applied frequencies and so they showed the typical flow behavior of a low molecular solution. However, for the hot water concentrates, G' predominated over G" at more than 1.9 rad/sec (cross-over point) and so they showed the typical flow behavior of a macromolecular solution.

• KSBB Journal
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• v.24 no.6
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• pp.563-569
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• 2009

Fibroin is an insoluble structural protein from Bombyx mori. It can be solubilized by dissolving in a hot $CaCl_2$ solution and subsequent dialysis. The aqueous solution is unstable and a transition from aqueous fibroin molecules rich in random coil is undergo to one rich in $\beta$-sheet content, resulting in hydrogelation. However, fibroin gel is so fragile and plastic that its mechanical property should be reformed for various applications. In this report, a semi-solid form of fibroin gel was prepared using glycerol and ethanol and was investigated to analyze their flow properties. A fibroin gel with 80% glycerol showed pseudoplastic and thixotropic properties. The square root of its yield stress varied linearly with fibroin concentration and it extrapolated to zero shear stress at 0.2% fibroin. A fibroin gel with 40% ethanol was shown to be highly thixotropic but its shear-thinning behavior was only observed above a certain level of shear rate. Its pseudoplasticity was restored by a high rate of shear stress.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.5
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• pp.681-687
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• 2020

Physicochemical properties of fucoidan and alginate extracted from Sargassium horneri were investigated. The alginates were extracted and purified via three different routes (CaCl₂, HCl and ethanol routes), and their rheological properties at various concentrations and temperatures were determined. The yield of fucoidan was 3.08%, and it was mainly composed of fucose and galactose. Fourier-transform infrared spectrum of fucoidan showed strong absorption band at 1,254 and 827 cm^-1 corresponding to the sulfate group. Flow behavior of the alginate solution was characterized using the power-law model. The consistency index increased with increasing concentrations. The sodium alginate solution (1.5%) exhibited Newtonian behavior when extracted via the CaCl₂ and HCl routes, while it exhibited pseudoplastic behavior when extracted via the ethanol route. The effect of temperature on the flow behavior was investigated in terms of the activation energy (E_a), which was obtained using the Arrhenius equation. The E_a value corresponding to the alginate solution decreased with increasing shear rates. The E_a values corresponding to the alginate solutions purified via the CaCl₂, HCl, and ethanol routes were 13.54-18.64 kJ/mol, 13.42-19.21 kJ/mol, and 9.51-10.67 kJ/mol, respectively. The low E_a values corresponding to the solutions extracted via the ethanol route suggest that the flow behavior does not depend significantly on temperature.

• Korean Journal of Food Science and Technology
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• v.19 no.4
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• pp.366-370
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• 1987

Rheological properties of gelatinized rice starch solutions (5%) were examined with a Brookifield viscometer. Gelatinized rice starch solutions showed pseudoplastic flow having yield stress, i.e., Binghamplastic flow behavior. The yield stress of gelatinized rice starch solutions was reduced by the phosphate. Phosphate increased the pseudoplasticity of gelatinized nonwaxy rice starch solutions. but decreased that of gelatinized waxy rice starch solution. The yield stress of gelatinized nonwaxy rice starch solutions held for one hour at $90^{\circ}C$ was slightly decreased, but that of waxy starch solution was reduced by 10-fold. Phosphate reduced the yield stress for both gelatinized nonwaxy and waxy rice starch solutions. Phosphate decreased the consistency index, but did not affect the flow behavior index of the gelatinized rice starch solutions.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.114-117
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• 1986

The rheological properties of arrowroot starch suspension (2-6%) were investigated with a tube viscometer. The starch suspensions of less $t^1$, 4% showed a dilatant behavior with no yield stress at the temperature range of $30-65^{\circ}C$. However, the starch suspension of 6% concentration showed a pseudoplastic behavior at $65^{\circ}C$. The consistency index was exponentially increased with the increase of the starch concentration. The activation energy of flow of the starch suspensions was 0.370-0.399 kcal/mole at $30^{\circ}-60^{\circ}C$ and 28-60 kcal/mole at $65^{\circ}C$.

• Journal of Pharmaceutical Investigation
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• v.35 no.3
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• pp.165-171
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• 2005

Itraconazole is a triazole antifungal agent to inhibit most fungal pathogens. However, it is difficult for itraconazloe to be delivered by topical system due to its poor aqueous solubility. First, niosomes containing drug were prepared with span 60, cholesterol. tocopherol and poloxamer 407 as vesicle forming agents in an effort to increase solubility of itraconazole. And then prepared niosomes were dispersed in O/W creams (containing xanthan gum, glycerin, vaseline, glyceryl monostearate and $Cerix^{\circledR}-5$) or gels (containing xanthan gum and poloxamer 407). Both creams and gels were evaluated with respect to their rheological properties, in vitro permeation through excised skin of hairless mouse. Creams or gels containing niosome showed pseudoplastic flow and hysteresis loop. For both creams and gels, viscosity was increased with increasing the content of glycerine or vaseline and the content of gel forming polymer, respectively. In creams, the permeability of drug to skin was decreased with increasing the viscosity of cream. The permeability of drug was affected by pH as well as viscosity of gel. In vitro permeation test results demonstrated that cream formulations showed better permeability than gels. In conclusion, these results suggest that creams formulation containing niosome can be useful for the topical delivery of intraconazole.

• Journal of Nutrition and Health
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• v.19 no.1
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• pp.3-15
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• 1986

This study was intended to investigate the rheological properties of the development formula of infant foods and the results are summarized as follow ; 1) Consistency of starch solutions measured by Brabender Anylograph and Brookfield viscometer showed that waxy rice and riece with malt had lower consistency and more rheological stability.The flow type of tested raw materials and formula was found to ？ pseudoplastic, as judged by n-value of 0.332 -0.692, and no yield value. 2) The influenced of temperature on consistency could be accounted for by the equation, In (n) = K(1/T) + const. this relationship indicated that consistency of tested sample increased as temperature decreased. The consistency of waxy rice, rice with malt and formula A were less affected by the temperature change. 3) Infant foods with malt(formula A ) ad with waxy rice maintained better freeze-thaw stability in terms of consistency and starch aggregation indicating that this infant food could be stored for a long term in the freezer section of the home refrigeratory without adverse effect on the product quality. 4) From the above experiments, it would necessarily follow that infant food can be easily made at home the food-stuffs generally available around us, and that the easiest and safest way to store them lies in making them into semisolid state, and in keeping them in frozen state.

• Preventive Nutrition and Food Science
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• v.13 no.4
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• pp.354-361
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• 2008

A novel bacterium isolated from Cheonggukjang was identified as a glutamate-dependent Bacillus subtilis HA with 98.3% similarity to Bacillus subtilis Z99104. Optimization of poly-$\gamma$-glutamic acid ($\gamma$-PGA) production by modulating fermentation factors including carbon sources, nitrogen sources, inorganic salts and fermentation time was investigated. Optimum culture broth for $\gamma$-PGA production consisted of 3% glutamate, 3% glucose and various salts, resulting in the PGA production of 22.5 g/L by shaking culture for 72 hr at $37^{\circ}C$. Average molecular weight of $\gamma$-PGA was determined to be 1,220 kDa through MALLS analysis. The $\gamma$-PGA solution showed a typical pseudoplastic flow behavior, and a great decrease in consistency below pH 6.0 regardless of the same molecular weight of $\gamma$-PGA. The molecular weights of isolated $\gamma$-PGA were drastically decreased by heat treatment in various acidic conditions, resulting in different hydrolysis of $\gamma$-PGA. The consistency of $\gamma$-PGA solution was greatly decreased with increase heating time in acidic conditions.

• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.269-274
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• 1995

For the screening of a new functional exopolysaccharide, sugar composition and rheological properties of exopolysaccharide produced from Xanthomonas sp. EPS-1 were investigated. The average molecular weight of exopolysaccharide was determined to be approximately 2.l $\times$ 10$^{6}$ dalton. The new exopolysaccharide EPS-1 was composed of mannose, glucose, galactose and gluco- samine. IR analysis showed that the exopolysaccharide EPS-1 was assumed to be polymer with carbohydrates. NMR analysis showed that exopolysaccharide EPS-1 was presumed to be 4 units of sugar and trace of CH$_{3}$ group. Exopolysaccharide EPS-1 solution showed a characteristic of non-Newtonian fluid properties. At the concentration of 1.0%, the consistency index and the flow behavior index were shown at 10.8352 poise-sec and 0.4419, respectively. All dispersions were pseudoplastic fluids described accurately by Power-law model. Exopolysaccharide EPS-1 was highly viscous at low concentration, with good stability over a wide range of pH 5 to 13. The excellent compatibility of exopolysaccharide EPS-1 was represented with salts such as sodium chloride.