Microstructure and rheology of heated foams stabilized by faba bean isolate and their comparison to egg white foams

Abstract This study investigates the microstructure and rheological properties of faba bean isolate (FBI) stabilized foams at pH 7 and 4 (addition of sugar or not), and compares with egg white (EW) under both unheated and heated foams. Unheated foams at pH 4 showed higher overrun, stability and more rigid structure, compared to those obtained at pH 7, due to the presence of larger protein aggregates surrounding the lamella structure. In contrast, EW foams displayed the highest overrun, but not stable as FBI foam at pH 4. After heating, FBI foams at pH 7 were nearly unaffected, whereas at pH 4, heating induced the formation of very large structures of aggregated proteins and caused the merging of air bubbles. For EW, heating seems to induce structural rearrangements with large protein aggregates closely attached to whole foam lamella. Sugar addition to FBI at pH 4 decreased the overrun and the stiffness, and the rate of liquid drainage. Upon heating, sugar contributed to maintaining a stable foam with higher G ′ and spherical bubbles. The toughest foams are the FBI at pH 4 after microwave heating. This study highlights the importance of studying the foaming properties of plant proteins under relevant environmental and processing condition.