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Se determinaron experimentalmente los tiempos de flujo de soluciones a NO3 + H2O en el intervalo de concentración molal 0,0000-0,9996 (mol/kg). Se usó un microviscosímetro automático Anton Paar®, modelo AMVn, a temperaturas desde 283,15 K hasta 318,15 K cada 5 K y presión atmosférica de 0,101 MPa. A partir de los datos obtenidos, se calcularon las viscosidades dinámicas (), los coeficientes de viscosidad,  y  de la ecuación de Jones-Dole,  y los parámetros de activación del flujo viscoso (,   y ) a dilución infinita. Los coeficientes  resultaron positivos al igual que . De acuerdo con el análisis del signo de este último, el NaNO3 actúa como un soluto formador de la estructura del agua. Por otro lado, los parámetros de activación del flujo viscoso a dilución infinita (,y) revelaron que el proceso de flujo viscoso es endotérmico con un claro predominio de las interacciones ión-solvente.

Ionic conditions affect the denaturation and gelling of whey proteins, affecting the physical properties of foods in which proteins are used as ingredients. We comprehensively investigated the effect of the presence of commonly used emulsifying salts on the denaturation and gelling properties of concentrated solutions of β-lactoglobulin (β-LG) and whey protein isolate (WPI). The denaturation temperature in water was 73.5°C [coefficient of variation (CV) 0.49%], 71.8°C (CV 0.38%), and 69.9°C (CV 0.41%) for β-LG (14% wt/wt), β-LG (30% wt/wt), and WPI (30% wt/wt), respectively. Increasing the concentration of salts, except for sodium hexametaphosphate, resulted in a linear increase in the denaturation temperature of WPI (kosmotropic behavior) and an acceleration in its gelling rate. Sodium chloride and tartrate salts exhibited the strongest effect in protecting WPI against thermal denaturation. Despite the constant initial pH of all solutions, salts having buffering capacity (e.g., phosphate and citrate salts) prevented a decrease in pH as the temperature increased above 70°C, resulting in a decline in denaturation temperature at low salt concentrations (≤0.2 mol/g). When pH was kept constant at denaturation temperature, all salts except sodium hexametaphosphate, which exhibited chaotropic behavior, exhibited similar effects on denaturation temperature. At low salt concentration, gelation was the controlling step, occurring up to 10°C above denaturation temperature. At high salt concentration (>3% wt/wt), thermal denaturation was the controlling step, with gelation occurring immediately after. These results indicate that the ionic and buffering properties of salts added to milk will determine the native versus denatured state and gelation of whey proteins in systems subjected to high temperature, short time processing (72°C for 15 s).

The apparent molar volumes and viscosity of DL-alanine in aqueous solutions of sodium sulfate, Na2SO4, at different molalities and in the temperature range (283 to 308) K at each 5K were determined from density measurements and flow times, using a vibratory tube densimeter Anton Paar DMA 5000 and an automatic viscometer AMVn, respectively. From these data, the: limiting apparent molar volumes and limiting apparent volumes of transfer, hydration numbers, viscosity coefficients of the Jones-Dole equation, and thermodynamic activation parameters of the viscous flow were calculated. The results indicate that the amino acid behaves as a structure-forming solute on the structure of the solvent, followed by an increase in the overall structure of the water. It is concluded that the formation of the transition state is accompanied by the establishment of intermolecular bonds and a more orderly structure of the species in the activated state.