Effects of microwave-vacuum pre-treatment with different power levels on the structural and emulsifying properties of lotus seed protein isolates

The present study investigated the changes in structural and emulsifying properties of lotus seed protein isolates (LSPIs) under different microwave-vacuum (MV) treatments. A decrease of fluorescence peak intensity with blue-shift of the fluorescence emission maximum indicated that MV treatment induced unfolding of LSPIs so that more hydrophobic residues were exposed. Raman spectra showed that the ordered secondary structures (α-helix, β-sheet) gradually converted into β-turns and random coils during 50-150 W MV treatment. Particle size distribution and atomic force microscope revealed that the amounts of small subunits increased when the LSPIs were modified by 50-100 W MV treatment. Emulsions prepared by 100-W-MV-LSPIs exhibited the optimal emulsifying ability with the smallest oil droplet sizes. Confocal laser scanning microscopy and analytical centrifugal analyzer further proved 50-100 W MV-treatment enhanced the flocculation and creaming stability. Our findings provide a certain theoretical foundation to apply MV technology for developing desirable LSPIs-stabilized emulsions.