A comprehensive study on structures and characterizations of 7S protein treated by high intensity ultrasound at different pH and ionic strengths.

ABSTRACT

High intensity ultrasound (HIU) effects on soy 7S proteins in various pH (pH = 3.0 and 7.0) and ionic strengths (I = 0.1, 0.3 and 0.5) were investigated. When dissolved in pH = 7.0, the 7S proteins formed aggregates at the low ionic strength (I = 0.1), while large aggregates were dissociated as the ionic strengths increased (I = 0.3 or 0.5) after HIU treatments. Moreover, the 7S proteins were unfolded at I = 0.3 and I = 0.5 through HIU. When dissolved in pH = 3.0, the 7S proteins were extensively positively charged, which favored the HIU-induced denaturation of the proteins. When the ionic strengths were increased, the larger aggregates of the proteins were found after HIU. The electrostatic screening from the ions was essential for the unfolding/refolding and aggregating behavior of the HIU proteins, which was also proved from the structural measurements. The current study illustrated that environmental factors were of great importance for the HIU effects on food protein functionalities.