• Korea-Australia Rheology Journal
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• v.12 no.3_4
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• pp.175-179
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• 2000

Rheological properties of chitosan solutions were investigated as a function of polymer concentration. The viscosity curves for chitosan solutions consisted of two distinct viscosity regions, the Newtonian zero-shear viscosity (η$_{0}$) region and the shear rate dependent apparent viscosity (η$_{app}$) region. The shear rate dependence of viscosity was more clearly observed at higher chitosan concentrations. The critical coil overlap parameter (C＊〔η〕) was determined to be approximately 3.2 from a plot of zero-shear specific viscosity η$_{sp,0}$ vs coil overlap parameter (C〔η〕), which was lower than C〔η〕4.0 reported for other random coil polysaccharides. It was also found that the slope of η$_{sp,0}$ vs C〔η〕 was 3.9 at concentrated C〔η〕>C＊〔η〕domain, while 1.2 at dilute C〔η〕$_{0}$ ${\gamma}$/${\gamma}$$_{0.8}$ relation.ion.n.n.

• KSBB Journal
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• v.10 no.4
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• pp.386-392
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• 1995

The high viscous ${\gamma}$-polyglutamic acid(${\gamma}$-PGA) from alkalophilic Alcaligenes sp. was purified and its solution property was investigated. The intrinsic viscosities for Na+ form and H+ form of ${\gamma}$-PGA were 31.1 and 0.38d$\ell$/g, respectively. The viscosity of H+-PGA was not influenced by pH or salts while that of Na+-PGA was influenced. The intrinsic viscosity of Na+-PGA solution decreased remarkably at the alkaline or acidic pH and showed the sharp decrease when salts were added. ${\gamma}$-PGA exhibited the property of the polyelectrolyte showing the .sharp decrease of intrinsic viscosity by the addition of NaCl, and intrinsic viscosity of dilute solution with the low concentration of NaCl was exponentially dependent on temperature and its temperature dependency increased with increasing NaCl concentration. The chain stiffness, coil overlap parameter and critical concentration of Na+-PGA were 0.08, 5.25 and 0.07g/d$\ell$, respectively.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.39-44
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• 2000

Highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its solution properties were investigated. The intrinsic viscosities for crude biopolymer and biopolymers purified by dialysis or CPC(cetylpyridinium chloride) treatment were 58.24, 73.60 and 42.18 dL/g, respectively. The intrinsic viscosity of biopolymer showed the maximum value at the neutral pH but it was decreased remarkably at the alkaline or acidic pH. Biopolymer exhibited the property of polyelectrolyte, showing the sharp decrease of intrinsic viscosity by the addition of NaCl. Intrinsic viscosity of dilute solution at the low NaCl concentration was exponentially dependent on temperature and its temperature dependency was increased with NaCl concentrations. The chain stiffness, coil overlap parameter, and critical concentration were 0.09, 5.25 and 0.07g/dL, respectively. Temperature dependency on intrinsic viscosity of biopolymer solution was different each other at $45^{\circ}C$. Flow activation energies at temperatures above $45^{\circ}C$ were constant, while those at temperatures below $45^{\circ}C$ increased with increase of added NaCl concentration.

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.590-597
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• 2000

The rheological properties of ${\beta}-glucans$ isolated from non-waxy and waxy barley were investigated. ${\beta}-Glucan$ solutions showed pseudoplastic properties and their behaviors were explained by applying Power law model in the range of concentrations$(1{\sim}4%)$ and temperatures$(20{\sim}65^{\circ}C)$. The effects of temperature and concentration on the apparent viscosity at $700\;s^{-1}$ shear rate were examined by applying Arrhenius equation and power law equation, and their effect was more pronounced in waxy ${\beta}-glucan$ solutions. The activation energy for flow of ${\beta}-glucan$ solutions decreased with the increase of concentration, and the concentration-dependent constant A increased with the increase of temperature. The intrinsic viscosity of waxy ${\beta}-glucan$ was higher than that of non-waxy ${\beta}-glucan$. The transition from dilute to concentrate region occurred at a critical coil overlap parameter $C^*[{\eta}]=0.02.$ The slopes of non-waxy and waxy ${\beta}-glucan$ at $C[{\eta}] were similar, but the slope of waxy ${\beta}-glucan$ at $C[{\eta}]>C^*[{\eta}]$ was higher than that of non-waxy ${\beta}-glucan$. Dynamic viscoelasticity measurement showed that cross-over happened, and storage modulus was higher than loss modulus at frequency range above cross-over. ${\beta}-Glucan$ solutions formed weak gels after stored for 24 hr.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.799-806
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• 1995

The steady shear and small amplitude oscillatory dynamic rheological properties of citrus pectin $([\eta]=3.75\;dL/g)$ were characterized for a wide range of pectin concentrations $({\sim}6%)$. The typical power-law flow was observed above 2.0% concentration, and the shear rate dependence of viscosity increased with pectin concentration. The transition from dilute to concentrated regime, determined from the double logarithmic plot of ${\eta_{sp.o}}\;vs\;C[\eta]$, occurred at a critical coil overlap parameter $C^{*}[\eta]\approx4.0$, at which ${\eta_{sp.o}}$ corresponded to approximately 10.0. The slopes of ${\eta_{sp.o}}\;vs\;C[\eta]$, at $C[\eta]\;at\;C[\eta]C^{*}[\eta]$were 1.1 and 4.5, respectively. The steady viscosity $(\eta)$ displayed a good superposition at ${\eta}/{\eta}_o\;vs\;{\gamma}/{\gamma}_{0.8}$ relation with an exception of high concentration (6%), which arised from the significant deviation of flow behavior index (n values of $\eta_{a}=K\gamma^{n-1}$) at high concentration. Dynamic measurements showed that the loss modulus $(G^{\prime\prime})$ was much higher than the storage modulus $(G^\prime)$for all concentrations studied, indicating predominant viscoelastic liquid-like behavior of pectin solutions. The frequency dependence of $G^\prime$ was higher than that of $G^\prime\prime$ at the same concentration, whose trend was more pronounced with decreasing pectin concentration. The shear viscosity $(\eta)$ was almost identical to the complex viscosity $(\eta^{*})$ at low concentration, following the Cox-Merz rule, but they became increasingly different at high concentration.