Heat treatment induced structural change and aggregation behavior of Moringa Oleifera seed salt-soluble protein

This study aimed to investigate effects of heat treatment temperatures (60degree celsius, 70degree celsius, 80degree celsius, 90degree celsius, 100degree celsius) and times (10 min, 30 min, 60 min) on the aggregation behavior of Moringa Oleifera seed salt-soluble protein (MOSP). With the increase of heating temperature and time, the MOSP solutions were changed from a more transparent state to a cloudy and opaque state, the absorbance value of the MOSP solution increased significantly, and the particle size gradually increased to a maximum of 1220.33 nm (100degree celsius, 30 min). The polymer dispersion index (PDI) also increased and the maximum PDI of MOSP (100degree celsius, 10 min) was 0.53, but the absolute value of the zeta-potential was gradually decreased. With the increase of heating temperature and heating time, the beta-sheet content of MOSP was increased to 30.8%, while the alpha-helix content of MOSP decreased. There was no obvious change in the subunit distribution of the heat-induced MOSP. The spectrum analysis displayed that heat treatment led to the exposure of the hydrophobic residues in MOSP, but as the heating temperature was further increased to 90degree celsius, re-embedding of the hydrophobic groups was observed due to the formation of aggregates. The total sulfhydryl group (-SHT) increased with the increase of temperature, while the free sulfhydryl group (-SHF)first decreased and then increased during short-term heating (10 and 30 min). The maximum content of -SHF reached 4.40% and the content of disulfide bonds was 11.97% (90degree celsius, 30 min). These changes could have a significant impact on protein products and might spur innovation in new protein applications.