AGGREGATION AND GELATION PROPERTIES OF EGG WHITE PROTEINS, AS AFFECTED BY HIGH INTENSITY ULTRASOUND

ARZENI, CAROLINA; PÉREZ, OSCAR E.; PILOSOF, ANA MR

Atenas

Congreso; 11th International Congress on Engineering and Food.; 2011

International Association for Engineering and Food IAEF

Among as many as 40 different proteins contained in the egg white (EW), the major proteins involved in the heat induced gelation are ovalbumin (54%), conalbumin (12%), ovomucoide (11%) and lysozyme (3.5%) . On the other hand, high-intensity ultrasound (HIUS), with a frequency range oscillating in between 16–100 kHz, and 10–1000Wcm2 of power, has immense potential for a wide variety of applications in the food industry. The goal of this contribution was determined the impact of HIUS application on the thermal aggregation and gelation of EW proteins solutions.EW solutions were sonicated for 20 min using an ultrasonic processor Vibra Cell Sonics, model VCX 750 (frequency: 20 kHz; amplitude: 20%). Before and after HIUS treatment, samples were heated and the aggregate size distribution was measured by light scattering using a Mastersizer 2000 with a Hydro 2000MU dispersion unit from Malvern Instruments Ltd, UK. The dynamics of gelation was registered upon time and temperature (70, 75, 80 and 85ºC) by a Phaar Physica MCR 300 rheometer, with controlled stress. The temperature was controlled by a Peltier system and a bath (Viscotherm VT2, Phaar Physica). Frequency sweeps were performed to characterize the generated structure of the gels. Surface hydrophobicity (Ho) of protein dispersions was determined according to the method of Kato & Nakai, (1980).The gelation temperature of HIUS-treated and control samples did not vary substantially when being isothermally heated at 70, 75, 80 and 85ºC. The equilibrium storage modulus (G´) increased with rising temperatures and after sonication. A structured network formation was not observed at 70ºC, since conalbumin is the only protein being denatured at this temperature. Structured network formation could only be seen at higher temperatures with the important ovalbumin contribution. Gelation rate was increased after applying ultrasound treatment. The formation of aggregates from protein solutions was accelerated by increasing heating temperatures. HIUS- treated samples generated aggregates with higher sizes at lower times.HIUS treatment impacted on the EW gelation properties studied here, since after its application gels were constituted more rapidly and presented higher G´ than the controls. This fact could be attributed to the increase in the hydrophobicity of the protein. With respect to the practical significance of ultrasonication, it could give improved functional properties with application to the design of new structures and textures.