Germination-Assisted Solid-State Fermentation as a Strategy to Enhance the Nutritional and Functional Quality of Pulse Protein Concentrates

Fermentation is increasingly applied to enhance and modify food ingredients. In this study, we investigated the impact of solid-state fermentation on the physical, nutritional, functional, and volatile properties of non-germinated and germinated faba bean and mung bean protein concentrates. Solid-state fermentation substantially reduced certain antinutritional factors, more pronounced in germinated faba bean (trypsin inhibitor activity: 3.70 to 2.19 TIU/mg; phytic acid: 2.94 to 1.52 μ g/g) and mung bean (trypsin inhibitor activity: 4.09 to 3.46 TIU/mg; phytic acid: 1.65 to 0.29 μ g/g) protein concentrates, while also leading to a decrease in protein digestibility. Fermentation significantly improved functional attributes, particularly water-holding capacity and foaming properties, across all samples. Short chain fatty acids, including acetic, isobutyric, and isovaleric acids, were markedly increased in the germinated faba bean (acetic acid: 2.65 to 6.68 mg/g; isobutyric acid: 0.00 to 0.71 mg/g; isovaleric acid: 0.00 to 0.78 mg/g) and mung bean (acetic acid: 3.49 to 8.61 mg/g; isobutyric acid: 0.23 to 0.79 mg/g; isovaleric acid: 0.05 to 0.91 mg/g) protein concentrates following fermentation. Pyrazine compounds originally presented in the protein concentrates was also greatly enhanced by fermentation, and a new volatile compound, 2,3-butanediol, was detected post-fermentation. Overall, the findings indicate that solid-state fermentation using Bacillus. subtilis improved the nutritional, functional, and volatile profiles of both germinated and non-germinated faba bean and mung bean protein concentrates. This work provides new insights into the application of fermentation for high-protein substrates and offers a promising route to enhance the value and sensory quality of pulse protein ingredients.