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The rheological properties of hydrotalcite-like compounds (HTlc)/sodium montmorillonite (MT) suspensions, which have formed gel-like structures, have been investigated. Special emphasis has been placed on the phenomenon of thixotropy. Usually, the structure recovery at rest after steady shear is considered the fundamental thixotropic process. And the recovery process was performed at the amplitude oscillatory shear measurements and the steady shear measurements. The oscillatory experiments were performed in the linear viscoelastic region so as to make the recovery process undisturbed. In the oscillatory experiments, η* increases monotonically with the time after the preshear process, and even after 3 h no equilibrium viscosity value of the suspension is reached. A single power law |η*| ∼ t n holds within the time regime from 10 s to 3 h, and the exponent n ) 0.158 ( 0.10 is not only independent of the concentration and composition of the clay and the HTlc but also independent of mechanical pretreatment of the suspension. In the oscillatory experiments, two kinds of Na-MT were used, and almost the same value of exponent n was obtained. This type of kinetics has not been reported so far for the thixotropic recovery in the mixed suspension. And the reorganization of the gel structure is interpreted as a cooperative self-delaying process similar to the aging of glassy polymers or precipitation from supersaturated solid solutions. In the steady experiments, the recovery process was monitored at the low shear rate, and η does not always increase with the time. In the recovery process, the formation of the network was disturbed by the shear rate to some extent. When the structure strength (which is indicated by the value of the viscosity) of the system is low, the disturbance of the shear rate on the recovery process is weak, which becomes distinct when the structure strength is high.

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A novel fructosyltransferase (AoFT) capable of synthesizing sucrose 6-acetate (S6A) from sucrose and glucose 6-acetate has been purified to homogeneity from Aspergillus oryzae ZZ-01. Its molecular mass was ~50 kDa by SDS-PAGE; optimal activity was at 45 °C and it was stable from pH 4.5 to 7.5 with an optimum pH of 6. Mg(2+), K(+) (5 mM), propanol, toluene (50%, v/v), Tween 20 or Triton X-100 (1%, w/v) increased the transfructosylation activity by 20, 17, 17, 10, 25 and 20%, respectively. An overall conversion of 32% was achieved under optimal conditions over 24 h. This is the first report that the purified and characterized the fructosyltransferase from Aspergillus capable of synthesis of S6A from sucrose and glucose 6-acetate.

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