Effects of the addition of sucrose and cellulose on the compression behaviour of ϰ-carrageenan gels

Influence of the concentration of sucrose and cellulose pulp on the compression behaviour of ϰ-carrageenan-based gels is studied. Composition of samples was established by using a second-order central composite design. Carrageenan concentrations used were between 0.5 and 1.25%, sucrose concentrations between 0 and 30% and cellulose fibre contents between 0 and 0.5%. Uniaxial compression behaviour was analysed by evaluating two parameters: maximum rupture strength (F_max) and apparent Young's modulus (E_ap). Results obtained showed that addition of sucrose increased both F_max and E_ap values while the effect of cellulose depended on the concentration of the other components.     

Adiabatic compression heating coefficients for high-pressure processing of water,propylene-glycol and mixtures – A combined experimental and numerical approach

The compression heating of water and water/propylene-glycol mixtures during high-pressure processing was studied using a purpose-designed experimental setup allowing for near-adiabatic conditions. The fluids were pressurised in a Stansted ISO-LAB FPG11501 HPP 3 L unit up to 750 MPa. Pressure/temperature profiles at varying initial temperatures (5–90 °C) were recorded and numerically evaluated to obtain pressure and temperature dependent compression heating properties of water/glycol mixtures at 0%, 25%, 50%, 75% and 100% glycol concentration. A further step was implemented in the numerical routine to derive the compression heating properties as function of pressure, temperature and glycol concentration.     

Brewster angle microscopy of adsorbed protein films at air–water and oil–water interfaces after compression,expansion and heat processing

Recent Brewster angle microscopy (BAM) observations of adsorbed films of proteins at the air-water (A–W) and oil–water (O–W) interfaces are reviewed and compared. At the A–W interface β-lactoglobulin (β-L) and ovalbumin (OA) were studied at pH 7 and 5. At the O–W interface β-L, α_s1-, β- and κ-caseins were studied at pH 7. The adsorbed films were periodically subjected to compression and expansion cycles such that the film area was typically varied between 125% and 50% of the original film area. At the A–W interface, little structure was observable on compression or expansion or aging, especially at pH 7. For ovalbumin at pH 5, some cracks and ridges in the films appeared. But, for both β-L and OA, such features became much more obvious on addition to the interface of a low area fraction (<0.01%) of 20 μm polystyrene latex (PS) particles. With particles present the structuring was also more obvious at pH 5 (closer to the protein isoelectric point) than at pH 7, and for greater adsorption times and/or higher bulk protein concentration (C_b). Particle addition was not necessary to highlight folding and ridges that occurred at the O–W interface for β-L. After heating to 80 and 90 °C, β-L films adsorbed from low C_b (0.005 wt%) even greater film structuring was evident. However, β-L films adsorbed from higher C_b (≥0.05 wt%) showed fewer, but more pronounced ridges and cracks. The caseins at the O–W interface showed comparatively little evidence of structuring, either before or after heating. A measure of the dilatational elastic modulus of the films correlated with the observed variations in the structural integrity of the films. Clearly, protein films subjected to these types of thermal and mechanical perturbations can become highly inhomogeneous, depending on the type of protein and the bulk solution conditions, with implications for the stability of the corresponding foams and emulsions. This is in agreement with earlier computer simulations. Protein films at the O–W interface (particularly after heating) appear to be more resilient and less aggregated than films at the A–W interface.     

Comparison of moisture-dependent orthotropic Young’s moduli of Chinese fir wood determined by ultrasonic wave method and static compression or tension tests

Wood with distinctively different properties in the longitudinal, radial and tangential directions exhibits a strong moisture-dependent material characteristic in the elastic range. The purpose of this study was to analyze the orthotropic elastic properties of Chinese fir wood [Cunninghamia lanceolata (Lamb.) Hook] determined at different moisture conditions using an ultrasonic wave propagation method. The results were compared with those obtained by the traditional static compression or tension tests. The results confirm that the stiffness coefficients obtained by the ultrasound without considering the complete stiffness matrix show significantly higher values than the compression or tension Young’s moduli in all the three anatomical directions at each specific MC. The differences between stiffness coefficients and Young’s moduli were significantly reduced by corrections with Poisson ratio. Only in tangential direction, the Young’s moduli with Poisson ratio correction are statistically equivalent to the Young’s moduli obtained by compression and tension.