EFFECTS OF HIGH ULTRASOUND INTENSITY ON FOAM STABILITY AND INTERFACIAL RELATIONSHIP OF SOLUBLE SOY PROTEIN ISOLATE

K. D. MARTÍNEZ; CARRERA SANCHEZ CECILIO

Rosario

Congreso; XIV Congreso Argentino de Ciencia y Tecnología de los Alimentos.?Hacia nuevos desafios en la innovación de alimentos, desarrollo sustentable y bienestar nutricional?; 2013

Asociación Argentina de Tecnólogos Alimentarios

The objective of this work was to determine the effect of ultrasound application on the stability of foams and interfacial properties at equilibrium conditions at pH 7 and 3 of soluble fraction of soy protein isolate (SSPI). In these conditions 1,73 and 0,43% of soluble protein were present respectively. The samples were sonicated for 20 min using an ultrasonic processor Vibra Cell Sonics, model VCX 750 at a frequency of 20 kHz and an amplitude of 20%. The foams were produced using a foaming commercial instrument (FoamScan, IT Concept, Longessaigne, France). Foam formation and stability were measured by conductimetric and optical methods. Moreover, the evolution of the bubble size change in the foam was determined by a second CCD camera. Measurements of the variations of surface pressure (π) with the molecular area (A) of films were analyzed at the air-water interface with an automated KSV Langmuir mini-trough (KSV Instruments Ltd., Helsinki, Finland). In spite of the better foam obtained after ultrasound treatment, trough the relative foam conductance ? Cf %-, the stabilizing parameters in the foam (characterized through three complementary parameters: (i) half-life time -t½-, (ii) relaxation time corresponding to the kinetics of liquid drainage from the foam ?td- and (iii) relaxation time corresponding to the kinetics of disproportionation and foam collapse ?tdc-) depended of pH studied which would be relating with the protein state and quantity of SSPI in each case. There are exist a shift of the -A isotherm to higher values of area when ultrasound were applied at pH 7, which could be related to solubilization of micro-aggregates in the sonication process. However, when ultrasound was applied at solution at pH 3 the resulting isotherm presented a similar behavior than the obtained from the untreated one. This, can be explain by the denaturing effect produced by the acidic solution.