Effect of high-power sonication pretreatment on extraction and some physicochemical properties of proteins from chickpea, kidney bean, and soybean

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

Submitted to: International Journal of Biological Macromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2019
Publication Date: 12/17/2019
Citation: Byanju, B., Rahman, M., Hojillaevangelist, M.P., Lamsal, B.P. 2019. Effect of high-power sonication pretreatment on extraction and some physicochemical properties of proteins from chickpea, kidney bean, and soybean. International Journal of Biological Macromolecules. 145:712-721. https://doi.org/10.1016/j.ijbiomac.2019.12.118.
DOI: https://doi.org/10.1016/j.ijbiomac.2019.12.118

Interpretive Summary: In this research, we found that using sound wave energy (high-power sonication) improved protein extraction yields in soybean flakes/flour, and chickpea or kidney bean flours and altered some protein properties that are beneficial for ingredient uses. Plant-based proteins are in high demand in the alternative proteins market; however, poor extractability and limited functionality are challenges in their commercial production. A physical technique being considered to aid plant protein processing is high-power sonication, which changes cellular and molecular structures in such a way that extractability and product quality could be enhanced. In the current work, we sonicated soy flakes and soy, chickpea or kidney bean flour at low or high power and then extracted the protein using conventional methods. We found that sonication resulted in a notable increase in extraction yield (almost 50%) of soy flakes protein. We also found that sonication caused changes to the protein native structure, such as breakage of certain bonds and unfolding, that helped improve extractability. Our results demonstrated that sonication is an effective technique for improving protein extraction yields and properties and a viable pre-extraction step for protein isolation. This research is useful to food ingredient processors and academic and industry researchers for designing efficient protein isolation methods that broadens the uses of plant-based proteins.

Technical Abstract: Impact of high-power sonication (HPS) as pretreatment in extraction and some physicochemical properties of proteins from soybean flakes, flour of soybean, chickpea, and kidney bean was evaluated. Soybean flakes and flours from soybean, chickpea, and kidney bean were dispersed in distilled water (1.10 w/v) and sonicated at two power densities (PD) of 2.5 and 4.5 W/cm3 for 5 min continuously. Proteins were extracted at pH range 8–8.5. PD 2.5 and 4.5 W/cm3 significantly increased protein extraction yields from soy flakes to 29.03% and 25.87%, respectively, compared to 15.28% for unsonicated controls, but did not increase for flours. Freeze-dried spent substrates at higher PD sonication aggregated in size. Free sulfhydryl content for both sonicated and unsonicated soy flakes and flour were similar but increased in chickpea and kidney bean when HPS of 4.5 W/cm3 was applied, indicating the unfolding of protein structure. The protein band patterns for sonicated and unsonicated legumes proteins were found to be similar, indicating no peptide profile alterations by HPS. However, circular dichroism analysis showed changes in secondary structure composition in extracted kidney bean protein causing unfolding and destabilizing the native structure. The secondary structure composition for soy flakes and flour protein and chickpea protein remained unchanged.