The combined treatments for breaking down microstructural barriers in highly denatured soybean meal to improve soybean protein concentrate processing

Abstract

The processing of soy protein concentrate (SPC) derived from highly denatured soybean meal (HDM) remains underexplored due to the inefficient ethanol leaching and the suboptimal functionalities of final product. The objective of this study is to investigate the impact of various pre-treatment, including grinding, alkaline soaking, Viscozyme L and alcalase hydrolysis, on the processing efficiency and functionalities of SPC. Additionally, mechanism was elucidated using near-infrared spectroscopy, fluorescence spectroscopy, scanning electron microscopy, and laser confocal microscopy. The results indicated that after grinding, 88.48 % of HDM particles were over 60 mesh (G₆₀) and accounted for 91.29 % of the total protein content; HDM particles, with size below 100 mesh, exhibited potential for SPC processing and achieved a protein purity level of 65.11 ± 1.76 %. Pre-treatment with Viscozyme L resulted in a protein purity of 59.29 ± 0.84 % for SPCs when G₆₀ was used; furthermore, the SPC exhibited more pronounced microscopic degradation features in cell walls. Simultaneously, levels of free sulfhydryl groups and β-sheet structures increased, accompanied by an enhancement in gel springiness and chewiness. In contrast, the SPC subjected to alcalase pre-treatment demonstrated an enhanced protein disaggregation and elevated nitrogen solubility index of 22.85, along with increased surface hydrophobicity and improved water holding capacity. In conclusion, these pre-treatments are effective in grading or disintegrating the microstructure of HDM while enhancing processing efficiency and regulating the functionality of SPCs; thus contributing to the comprehensive utilization of highly denatured oilseed meals.