EFFECTS OF ULTRASOUND TECHNOLOGY ON FOAM STABILITY OF SOY PROTEIN ISOLATE AND HYDROXYPROPYLMETHYLCELLULOSE MIXED SYSTEM AT DIFFERENT PHS

K. D. MARTÍNEZ; CARRERA SANCHEZ CECILIO

Rosario

Congreso; 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 of mixed systems of soy protein isolate and a hydroxypropylmethylcellulose called E4M at pH 7 and 3. In these conditions 1,73 and 0,43% of soluble protein were present respectively. 0.25% of polysaccharide were added and finally treated. 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. From these equipment, the relative foam conductance (Cf%) and complementary parameters: half-life time t½, relaxation times corresponding to the kinetics of liquid drainage, td, disproportionation and collapse, tdc were obtained. The ultrasound application provoked a decrease of the foamed system of the relative conductance at pH 7 showing a more air incorporation in the foam with the treatment. However at pH 3 no differences were found. Regarding the half-life time, no changes were observed as same way at both pH studied. In the other hand, very significant differences were found for the relaxation times td and tdc at pH 7 as a consequence of the ultrasound treatment. It could be seen that ultrasound promoted a great increment of these relaxation times in these conditions, meaning a decisive beneficial effect of the treatment improving the parameters related to stability of foams. However, at pH 3 no changes were observed on soy protein isolate-polysaccharides systems. In conclusion, the modifications produced by ultrasound technique are sensibly influenced by the pH studied, showing that pH 7 are better conditions to improve foamed mixed systems stability by high power ultrasound.