Properties of protein isolates extracted by ultrasonication from soybean residue (okara)

Soybean protein extraction was evaluated using conventional (alkaline phosphate buffer) and ultrasonication assisted methods. The impact of the extraction method on protein yield, chemical composition, and structural properties of the protein isolates was assessed. In conventional alkaline extraction, increasing pH values (from 9 to 12) led to an increase in the protein yield, with pH 12 favouring protein extraction, with yields up to 36 % (w/ w). Ultrasonication process at the same pH, led to maximum protein extraction yield of 84 % (w/w). Secondary structural changes in ultrasonicated OPI samples were linked to cavitation effects and the duration of the extraction, rather than the intensity of ultrasonication process. Extracted proteins exhibited increased beta-sheet content, improved zeta-potential and smaller particle size of ultrasonicated proteins, rendering them suitable ingredients for tailored food applications.

Automated summary

The study compared the conventional and ultrasonication assisted methods for soybean protein extraction. Results indicated that ultrasonication assisted extraction could achieve higher protein yield and improve the structural properties of the proteins extracted.