Enzymatic production and physicochemical and functional properties of sorghum protein isolates

Grain sorghum has emerged as a promising source for producing alternative proteins, yet current extraction methods lack efficiency. In this study, a novel enzymatic approach using α-amylase and cellulase on sorghum materials was developed to address this challenge. Comparisons were made among the proteins isolated from dry-milled sorghum flours, wet-milled sorghum gluten meals, and sorghum dried distiller's grains (DDG). Remarkably, proteins obtained from sorghum gluten meals demonstrated the highest protein purity (83-85 %) and recovery rate (92-93 %), followed by those from sorghum flour (purity 75-76 %) and DDG (purity 45-50 %). Physicochemical properties and functionalities of the isolated sorghum proteins were analyzed and compared with common commercial plant proteins (e.g., soy protein isolate, pea protein isolate, and wheat gluten). Sorghum proteins exhibited higher levels of crude fat content, α-helix, and random coil structures, along with higher surface hydrophobicity and oil holding capacity (OHC) compared to the commercial plant protein isolates. Notably, proteins extracted from sorghum flours displayed slightly higher α-helix and random coil structures, total sulfhydryl content, water holding capacity (WHC), OHC, and protein digestibility compared to proteins isolated from sorghum gluten meals. Overall, this study demonstrates that enzymatic processing is feasible in producing sorghum proteins and provides insights into their basic properties and functionalities.