Physicochemical characteristics and structural changes of fermented faba bean extrudates prepared by twin-screw extrusion

• Addition of LBG in the blends influenced the expansion and density of extrudates. • Changes in secondary structure of protein were correlated with physical properties. • CLSM allowed visualization of changes in the protein and starch during processing. • Microstructure of expanded extrudates showed open cell structure with thin cell walls. In this study, fermented faba bean blends with different locust bean gum (LBG) contents were processed in a co-rotating twin-screw extruder. The effects of extrusion process variables and the LBG level on physicochemical, sensory and structural characteristics of expanded extrudates were investigated. The results showed that physical characteristics of extrudates including expansion, apparent density and texture were significantly affected by variation of screw speed and die temperature, but the effect of LBG level was only significant for expansion and density. FTIR-ATR analysis revealed that a significant change occurred in the protein secondary structure as well as in the short-range ordered molecular structure of starch during fermentation and extrusion. The X-ray diffraction patterns of extrudates exhibited V-type pattern. Microstructure of the extrudates analyzed by FE-SEM exhibited variations in cell size and wall thickness depending on extrusion processing conditions and LBG level, which in turn lead to different textural perceptions.