This paper introduces a novel strategy for the fabrication of ultra-stable protein foams mediated by transition metal ions. Specifically, the transition metal ion Fe(II) was utilized as the foam stabilizer for hydrolyzed pumpkin seed protein (HPSP) in this study. To maximize foaming performance, response surface methodology (RSM) was utilized to optimize key process parameters in hot-alkali experimental setups. The experimental findings indicated that the optimal reaction conditions were identified as a pH of 11.5, a temperature of 55 ℃, and a reaction time of 1.5 h; under these conditions, the HPSP foaming agent exhibited the highest foaming volume of 488 mL. The interaction and the mechanism of foam stabilization between transition metal ions Fe(II) and HPSP were studied. The results of high performance liquid chromatography (HPLC) showed that the HPSP solution contained a large amount of isoleucine which was beneficial to the stability of foam. Low temperature transmission electron microscopy (Cryo TEM) and small angle X-ray scattering (SAXS) experiments have confirmed that the addition of Fe(II) promotes the exposure of hydrophobic groups in proteins and increases the size of aggregates. Meanwhile, the properties of foam and foamed concrete prepared using self-made foaming agent (Fe-HPSP) and plant protein foaming agents readily available on the market (PS) were studied. Experimental findings reveal that HPSP foams incorporating Fe(II) exhibit enhanced density, stability and viscosity. Furthermore, the resistance to shrinkage and homogeneity of the resultant foamed concrete are also improved. This research offers a novel strategy for the advancement of protein-based foaming agents.
Song et al. (Tue,) studied this question.