Structural, functional properties of protein and characteristics of tofu from small-seeded soybeans grown in the Loess Plateau of China

The structural, functional properties of protein isolated from small-seeded soybeans were investigated and characteristics of tofu were studied. Small-seeded soybean protein had obvious α', α, β, acidic and basic subunits bands and two endothermic peaks (76.02–76.63℃ and 91.94–94.25℃). Small-seeded black soybean protein isolates (SBSPI) had more β-sheet (31.90–33.54%) structure, while small-seeded yellow soybean protein isolates (SYSPI) had more α-helix (18.89–20.72%) structure. SYSPI had higher fluorescence intensity (839.10–847.80) than SBSPI (482.70–565.10). SBSPI exhibited higher surface hydrophobicity (939.51–1252.75) and water absorption capacity (8.07–8.50 g/g). Tofu made from small-seeded yellow soybeans had higher yield (549.46–560.23 g/100 g soybean) and was brighter (L*, 74.61–77.48) and more yellowish (b*, 14.83–14.95) in color. Tofu made from Fugu small-seeded black soybean (FGSBS) had the highest hardness (178.52 g), adhesiveness (-25.77 g.sec), chewiness (87.45 g) and resilience (0.26), signifying a more compact structure.