Characterization of beta-lactoglobulin A gelation in the presence of sodium caprate by ultrasound spectroscopy and electron microscopy

The effect of sodium caprate (a fatty acid salt) on the formation of beta-lactoglobulin A gels was studied at constant temperature (30 or 35 degrees C) using ultrasonic spectroscopy. During incubation at these temperatures, ultrasonic attenuation increased with the addition of sodium caprate, and reached a plateau after 5-7 h of incubation. Comparing beta-lactoglobulin A with and without sodium caprate, a decrease in net ultrasonic velocity was observed. These results suggested that aggregation occurred during incubation with sodium caprate, and the sample showed an increase in compressibility. Transmission electron microscopy with negative staining showed the formation of filamentous aggregates of beta-lactoglobulin A at around 3-4.5 h of incubation with sodium caprate. These results demonstrated that sodium caprate induced the formation of structures with unique gel properties compared to those formed by heating beta-lactoglobulin in the presence of NaCl alone.