The objective of this paper was to determine the effect of sodium chloride addition on rheological properties of foams obtained from powdered high whip albumin. Solutions were made from albumin preparation used in the investigation; their albumin concentration rates were: 2, 6, and 10 %. The following molar concentration rates of NaCl solutions were applied [mM]: 60, 120, 240, and 480. The foams were produced by whipping 50 ml of the solution in lab high-wall beakers of 600 ml volume using a Philips Essence mixer. The whipping time for each solution sample was 2 minutes. The rheological properties of foams were analyzed using an oscillatory ThermoHaake RS 300 rheometer (ThermoHaake, Karlsruhe, Germany). The yield stress (τo) measurements were performed at a constant shear velocity of 0.01 s-1 using a vane tool and a system of two plates that were parallel to each other. In the oscillation test, a linear range of viscoelasticity of foams analyzed was determined at a frequency of 1 Hz and for the deformation range between 0.002 and 0.05 %. Furthermore, the storage (G’) and loss (G”) moduli were determined as was the phase angle (δ) value for the oscillation frequency ranging from 0.1 to 10.00 Hz and for the deformation rate of 0.003 %. The measurements were three times repeated. Also, for all the solutions investigated, the values of foam overrun (Φ) were calculated. The rheological properties of the foams produced depended on the concentration rates of the preparation applied and NaCl. The foams produced from the solutions with the highest albumin concentration were characterized by the best rheological properties. The increase in the molar concentration of NaCl to a value of 120 mM in the solutions analyzed caused the yield stress and overrun increase to systematically increase. However, when the sodium chloride concentration continued to increase, the values of the above indicated parameters decreased, thus, proving the deterioration of the rheological properties of foams under analysis.
albumin, NaCl, foams, rheological properties