Adsorption of microgel aggregates formed by assembly of gliadin nanoparticles and a β-lactoglobulin fibril-peptide mixture at the air/water interface: Surface morphology and foaming behavior

Foamability, foam stability, foam rheological properties, and foam plasticity of foaming agents are key parameters in determining the quality of foamed food, but with current foaming agents these parameters are difficult to optimize simultaneously. In this study, gliadin nanoparticles (GNPs) were mixed with a β-lactoglobulin fibril-peptide mixture (β-lgFP) to determine their assembly mechanism, and foaming properties of the resulting aggregates at a pH of 3.0–7.0. Structural information of GNP-β-lgFP aggregates was obtained using CLSM, TEM, and SEM. When mixing GNPs with β-lgFP solutions, at a pH of 3.0–6.0, the GNPs with small size adhered to the surface of the fibrils. GNPs and β-lgFP then assembled into microgel network structures. GNP-β-lgFP aggregates at a pH of 3.0–6.0 had the ability to adsorb to the air/water interface and form a dense microgel surface structure. Aggregates with pH of 4.0–5.0 possessed remarkable foamability (>265%), high foam stability (t1/2>18 h), and a uniquely high viscoelastic modulus, even at very low concentration of GNP-β-lgFP (GNPs~1 mg/mL and β-lgFP~1 mg/mL). By mixing β-lgFP with GNPs, the β-lgFP prevented the fusing of GNPs at the air/water interface. Shaped foams made from aggregates (GNPs~8 mg/mL and β-lgFP~8 mg/mL) at a pH of 4.5 show better shape retention than egg white foams. These results demonstrate that GNP-β-lgFP aggregates could act as an efficient foaming agent and could be applied in the field of foamed food products.