• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.85-89
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• 2005

An aim of this study is to study the correlation between rheological properties and sedimentation of capsules in aqueous polymer solution with low viscosity. Rheological properties of aqueous polymer solutions were controlled by carbomer (C), acylate/C10-30 alkyl acylate crosspolymer (AC), and ammonium acryloyldimethyltaurate/VP copolymer (AV). Small amount of polymer C solution had the highest viscosity and yield stress of polymer AV solution was higher than that of polymer C solution in the same viscosity when the concentration of polymer AV exceeded $0.35 wt\%$. Each aqueous polymer solution was tested and the results showed that as viscosity and yield stress increased, the sedimentation ratio of capsules decreased. The viscoelasticity data also showed the same tendency in a shear stress range of 0.1 to 2.0 Pa. These results demonstrated that the rheological properties of polymer solutions had a strong correlation with the sedimentation of capsules. When polymer I and AV were used, there was a synergistic effect and the correlation between rheological properties and sedimentation of capsules was very complicated. It was assumed that the characteristics of polymer structure and interaction between polymers caused this phenomena.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.438-442
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• 2005

Granule swelling is essential phenomenon of starch gelatinization in excess water, and characteristic of heated starch dispersion depends largely on size and distribution of swelled starch granule. Although swelling characteristic of starch granules depends on type of starch, heating rate, and moisture content, influence of heating rate on swelling phenomenon of starch granule has not been fully discussed, because constant heating rate of starch dispersion cannot be obtained by conventional heating method. Ohmic heating, electric-resistant heat generation method, applies alternative current to food materials, through which heating rate can be easily controlled precisely and conveniently at wide range of constant heating rates. Starch dispersion heated at low heating rates below $7.5^{\circ}C/min$ showed Newtonian fluid behavior, whereas showed pseudoplastic behavior at heating rates above $16.4^{\circ}C/min$. Apparent viscosity of starch dispersion increased linearly with increasing heating rate, and yield stress was dramatically increased at heating rates above $16.4^{\circ}C/min$. Average diameter of corn starch granules during ohmic heating was dramatically increased from $30.97\;to\;37.88\;{\mu}m$ by increasing heating rate from $0.6\;to\;16.4^{\circ}C/min$ (raw corn starch: $13.7\;{\mu}m$). Hardness of starch gel prepared with 15% corn starch dispersion after heating to $90^{\circ}C$ at different heating rates decreased gradually with increasing heating rate, then showed nearly constant value from $9.4\;to\;23.2^{\circ}C/min$. Hardness increased with increase of heating rate higher than $23.2^{\circ}C/min$.