Heat induced structural transitions of PA1 and PA2 albumins from pea

Pea albumins are the soluble fraction of pea proteins, recovered as a side stream of the isoelectric precipitation. The time-resolved heat-induced structural transitions of the whole fraction of pea albumin (PA) were studied by evaluating the structure of the two main fractions, PA1 and PA2. Synchrotron radiation circular dichroism (SR-CD) spectroscopy showed that the secondary structure signature for PA1 remained unchanged at temperatures up to 85°C. In contrast, PA2 underwent a change in secondary structure between 45 and 70°C. These thermal transitions were also confirmed by Nano Differential Scanning Calorimetry (Nano-DSC). Small-angle X-ray scattering (SAXS) in situ experiments were also carried out, and high-resolution structural models of PA1 and PA2, derived from the AlphaFold Protein Structure Database, were used for data analysis. PA1 maintained a consistent local structure with a radius of gyration ∼17 Å across all temperatures, but formed small soluble aggregates above 60°C, as evidenced by an upturn at low q . PA2 scattering resulted from its dimeric structures and transitioned to unfolded structures after 60°C. The unfractionated PA scattering showed good agreement with a linear combination of PA1 and PA2 scattering. This was also confirmed by the structural behavior of the purified PA1+PA2 mixture, which closely resembled that of PA2, though the PA2 component remained partially folded even after heating above 70°C. This study brings new knowledge on the contribution of the two main components of pea albumins in the thermal behavior of this novel extract, with great potential to be used as a functional food ingredient. • PA1 and PA2 contains higher β-sheet compared to α-helix; • Heat induced aggregation of PA can be modeled after a combination of PA1 and PA2; • PA1 maintains a consistent local structure, but forms soluble aggregates above 60°C; • PA2 transitions from dimer to unfolded structure above 60°C.