Impact of high-power sonication on yield, molecular structure, and functional properties of soy protein isolate

Authors: RAHMAN, MD MAHFUZUR - Iowa State University; Hojilla-Evangelista, Milagros - Mila; LAMSAL, BUDDHI - Iowa State University

Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2022
Publication Date: 5/20/2022
Citation: Rahman, M., Hojilla-Evangelista, M.P., Lamsal, B.P. 2022. Impact of high-power sonication on yield, molecular structure, and functional properties of soy protein isolate. Innovative Food Science and Emerging Technologies. 79. Article 103034. https://doi.org/10.1016/j.ifset.2022.103034.
DOI: https://doi.org/10.1016/j.ifset.2022.103034

Interpretive Summary: Plant-based proteins are in high demand in the alternative proteins market; however, poor extractability and limited functionality are challenges in their commercial production. High-power sonication (HPS, using sound wave energy to enhance chemical and physical transformations) is a green technology that is generating high interest for use in extraction of plant-based proteins to maximize the amount of recovered protein and modify their functional properties. In this research, HPS was applied at different energy levels and duration to aqueous slurries of defatted soy flakes or flour before extracting the protein using the conventional method. Researchers at ARS in Peoria, Illinois, and Iowa State University found that HPS shortened the soy protein extraction time and increased the yield of protein isolate, with the yield improvement more notable from flakes as starting material than when using flour. HPS also enhanced the emulsification (combining water and oil into one phase) and foaming properties of the soy protein isolates. However, HPS caused more notable changes in the structure of protein isolated from flour, particularly when longer extraction times were used. These research findings will benefit food or ingredient processors and academic and industry researchers in designing efficient protein isolation methods that also improve protein properties, which then broadens the uses of plant-based proteins thereby adding revenue to all participants in the value-chain.

Technical Abstract: This study reports the influence of high-power sonication (HPS) pre-treatment on protein yield, molecular structure, and functional properties. HPS energy densities (0–720 J/mL) were applied to soybean flour and flakes prior to protein extraction at pH 8.5 for 15 or 30 min at 600C, and 5 min at room temperature. The isolates were prepared by precipitating at pH 4.5 and had >90% protein. HPS of 720 J/mL to flakes substrates extracted 80% protein without any incubation and 85% with 15 min incubation when no-sonication control showed an extraction of 71%. FTIR showed some aggregation and intrinsic fluorescence and free SH content showed pronounced effects on isolates from flour. HPS increased the surface hydrophobicity, reduced solubility, and enhanced the emulsification and foaming properties for a few treatments. Therefore, incubation duration changed structural and functional properties more prominently than did HPS in the isolates from flour than flakes.