FOAMING PROPERTIES OF MODIFIED FABA BEAN PROTEIN ISOLATES

The foaming properties of native and modified faba bean (Vicia faba) protein isolates were investigated. Foam stability was studied using both a micro-conductimetric/sparging and a whipping method. Samples were defatted by either supercritical carbon dioxide or isopropanol extraction, both of which produced an increase in the foam stability. Increases in form stability were also observed for acetylated and mechanolyzed (ball milled) samples. The latter produced the more marked effect. Samples with differing degrees of mechanolyzation were examined, the most highly mechanolyzed samples displaying the greatest foam stability. Studies using circular dichroism spectroscopy showed a correlation between the observed change in functional properties and the secondary structure of the faba bean protein. The robustness of foams formed from several of the treated samples was investigated by assessment of the stability of the foams against destabilization by competitive adsorption of the lipid analogue lysophosphatidylcholine. Again the mechanolyzed sample possessed the best foaming properties in the presence of this competitive surfactant.