In-depth exploration of the structure of pea albumin, its fractions and their heating and foaming properties

The structure and functionality of pea albumin can be described in detail as a combination of its main fractions, PA1 and PA2. PA1 and PA2 were purified from a Pea Albumin extract (PA) using size exclusion chromatography, and characterized by two-dimensional gel electrophoresis. Their secondary structure was analyzed using Fourier-Transform Infrared Spectroscopy (FTIR). The structures before and after heat treatment (90 °C, 1 & 5 min) were investigated by Small-Angle X-ray Scattering (SAXS). SAXS intensities were evaluated using high-resolution models obtained as predictions from the AlphaFold Protein Structure Database. Interfacial and foaming properties were also evaluated. Both PA1 and PA2 contained various isoforms, and PA2 displayed a high β-sheet/α-helix ratio. In solution, SAXS intensities of PA1 could be predicted by its native structure, and after heating PA1 showed limited aggregation. PA2 could be presented as a dimer, which unfolded and formed large aggregates during heating. The high-resolution models could also explain well the SAXS signal of the unfractionated PA, combining PA1 and PA2. After heating, PA2 dominated the properties of the PA mixtures. PA2 predominantly contributed to the interfacial and foaming properties of PA, in spite of both PA1 and PA2 showing adsorption at the air/water interface. Indeed, PA1 in isolation could not form a stable foam. SAXS data analyzed with high-resolution structure models allowed for an in depth understanding of the structural changes of PA1 and PA2, and provided a mechanistic understanding of the relationships between structure, composition, and technological functionality of the albumin fractions from pea.