Paweł Ptaszek

Dynamics of heat-integrated pseudohomogeneous tubular reactors with axial dispersion

The study concerns a theoretical analysis of pseudohomogeneous autothermal tubular reactors with axial dispersion of mass and heat. Based on analysis and simulations it is demonstrated that such a system can generate complex oscillatory profiles of temperature and concentration-periodic or chaotic. These profiles, especially those of aperiodic character, can seriously impair the performance of the system. The effect of three parameters on the reactor dynamics is studied, namely, the cooling medium temperature, the Lewis number and the Peclet number. We consider only relatively small values of the Lewis number in this paper.

The Physical and Linear Viscoelastic Properties of Fresh Wet Foams Based on Egg White Proteins and Selected Hydrocolloids

The aim of this work was to evaluate the physicochemical properties of fresh foams based on egg white proteins, xanthan gum and gum Arabic. The distributions of the size of gas bubbles suspended in liquid were determined, as well as density and volume fraction of gas phase of the generated foams. Additionally, the viscoelastic properties in the linear range were measured, and the results were analyzed with the use of the fractional Zener model. It was shown, that foam supplementation with hydrocolloids considerably decreased their volume fraction of gas phase in comparison to pure egg white protein-based foams. Application of gum Arabic did not cause an increase in the size of foam bubbles when compared to pure white egg foam, whereas application of xanthan gum significantly decreased the size of the bubbles. Application of the fractional Zener model allowed to determine the relaxation times, their intensity in analyzed suspensions and also equilibrium module (Ge). The increase in the concentration of xanthan gum resulted in the prolongation of the relaxation time and increased its intensity. Gum Arabic, when added, weakened the viscoelastic properties of the mixture as a viscoelastic solid.

The effect of structural properties on rheological behaviour of starches in binary dimethyl sulfoxide-water solutions

This research study analysed the rheological properties of potato amylose and potato amylopectin in binary solutions of the following water and dimethyl sulfoxide concentrations: 90% DMSO (1), 80% DMSO (2) and 50% DMSO (3), with preparation methodology involving the dissolution at the temperature of 98°C. The studies of dynamic light scattering on the biopolymer coils and the determination of main relaxation times of the solutions were carried out. For the amylose solutions, the fast relaxation phenomena are predominant. The results of the quality tests of the hysteresis loop showed, that the amylose solutions in the solvents (1) and (2) are rheologically stable and shear-thickened. The amylose solutions in solvents (3) reveal oscillatory alterations of viscosity in the time. Amylopectin solutions are characterized by 80% share of slow relaxation phenomena, very low diffusion coefficients and hydrodynamic radii in the range of 2000 nm. The amylopectin solutions are rheologically unstable.

The effect of temperature on the colligative properties of food-grade konjac gum in water solutions

This research paper presents the results of tests on the colligative properties of konjac gum chains in water solutions. For this purpose, the measurements of osmotic pressure and intrinsic viscosity of aqueous solutions, in the function of konjac gum concentration and temperature were carried out. The applied methods allowed for the determination of the second osmotic virial coefficients B2, which raised with the increase of temperature. It indicate that increase of temperature causes higher affinity of polysaccharides chains to water. It was determined, that the osmotic average molecular mass of the konjac gum in non-purified solutions increases with temperature (1.07×105-3.80×105g×mol-1). Values of the reduced viscosity linearly increased in range 18-29dL×g for all temperatures. Received values of the Huggins constant (0.81-1.72) lead that water is poor solvent for konjac gum. The theta (θ) conditions were extrapolated for non-purified solutions - 325K (52°C), and interpolated for purified solutions - 307K (34°C). Based on the results of tests using the dynamic light scattering, the values of two main relaxation times (fast - 0.4-1.8ms and slow components - 4300-5500ms) were determined (the Kohlrausch-Williams-Watts). The obtained autocorrelation functions were characteristic for sol type systems or these which indicate a gel-like structure.

β -Cyclodextrin as water-solubility enhancer for butylated hydroxytoluene

The phenomenon of the increase in solubility of the non-polar phenolic antioxidant — butylated hydroxytoluene (BHT) — in aqueous solutions containing β-cyclodextrin (CD) was studied. The complexation of BHT by CD was investigated using a phase solubility study. This method makes it possible to calculate the apparent formation constant for the host-guest complex. In addition, the thermodynamic properties were evaluated, revealing a spontaneous endothermic process of complex formation. Two solubility models were also used to verify their applicability to predicting the BHT concentration in solution. Those models included the modified Apelblat and Buchowski-Ksiazczak equations. In order to investigate the antioxidant properties of the BHT/CD/water ternary systems, a radical scavenging activity using a DPPH stable radical was performed. The experiments indicated that the antioxidant activity is temperature- and CD concentration-dependent. It was shown that complexation may inhibit the radical scavenging by BHT or change the scavenging stoichiometry.

Food Rheology: Scientific Development and Importance to Food Industry

The focus of food rheology has been gradually moved toward oscillatory and creep measurements from the conventional steady flow measurement. Recent evolution of tribology synchronized the measurement of food texture with the dynamic of oral processing and opened a new area of rheological study. Rheological and tribological attributes at different oral processing phases have been established to strongly impact texture perception. Several new other areas of rheological measurements and concepts including large amplitude oscillatory shear (LAOS), extensional rheology, Fourier transformation rheometry, time–temperature superposition principles (TTSP), gel rheology have been introduced, and a great impact of these measurements is anticipated in the area of product development and quality control of food products.