Structure and Functionality of Fermented Faba Bean: Influence of Particle Size and Rhizopus spp.

This study investigated the influence of particle size and Rhizopus species on the fermentability, structure, and functionality of faba bean (Vicia faba L.) during controlled solid-state fermentation. Split seeds, coarse particles, and 1000–2000 µm fractions were fermented with either R. oryzae or R. oligosporus. Analyses included compositional profiling, SDS-PAGE, FTIR, DPPH antioxidant activity, phytic acid quantification, and rheological yield stress measurements. Particle size strongly affected mycelial growth and matrix structure: coarse particles supported more uniform mycelial networks, particularly with R. oryzae. After 48 h of fermentation, total protein and phytic acid contents remained largely unchanged; however, SDS-PAGE and FTIR results indicated proteolysis and alterations in secondary structure, accompanied by higher antioxidant activity. Rheological data showed significant species–particle size interactions influencing yield stress, with R. oligosporus-fermented samples exhibiting higher yield stress than those fermented with R. oryzae. Overall, these findings demonstrate that optimising particle size and fungal strain combinations can enhance the structural and functional characteristics of fermented faba bean.