Effects of Direct Steam Injection and Spray‐Drying on the Physicochemical, Nutritional, and Functional Properties of Black Bean Protein Concentrates

ABSTRACT Direct steam injection (DSI) and spray‐drying are key unit operations in the industrial production of pulse protein ingredients that are often overlooked in laboratory‐scale studies. In this study, black bean protein concentrates were treated with DSI (130°C/15 s or 145°C/4 s), then freeze‐dried or spray‐dried to understand how these processing methods impact the physicochemical, nutritional, and functional properties of the proteins compared to a typical laboratory control (non‐thermally treated, freeze‐dried). DSI extensively denatured the bean proteins, as the denaturation enthalpy of the proteins decreased from 12.1 J/g protein (control) to 1.2–1.4 J/g protein (all DSI treatments). DSI‐induced denaturation led to a significant increase in surface hydrophobicity and a decrease in surface charge. However, a decrease in particle size was observed for all DSI‐treated samples, which could be attributed to the high cavitation and shear of the DSI process. Trypsin inhibitor activity remained unchanged (35–39 TIU/mg powder), while in vitro protein digestibility was significantly enhanced by DSI (74%–76%) compared to the control (43%), indicating that DSI‐induced structural modifications were the main driver for improved protein digestibility. All DSI‐treated samples exhibited lower solubility at pH 4 and decreased emulsifying capacity, but they generally displayed similar foaming properties as the non‐treated control. Protein gels produced with the DSI‐treated samples also had higher gel hardness but lower springiness compared to the control. Overall, the results in this study demonstrate that DSI was responsible for most of the changes observed in protein properties, while minimal differences were observed between spray‐dried and freeze‐dried protein concentrates.