Effect of Protein Content and Particle Size on Functional Properties of Air-Classified Fava Bean Flour Fractions

Abstract

The objective of the study was to evaluate the effects of air classification speed on the physicochemical and functional properties of fava bean flour fractions. Fava bean flour (CTL) was air classified and separated into fine (protein-rich) and coarse (starch-rich) fractions at varying wheel speeds of 20 Hz, 25 Hz, 30 Hz, and 35 Hz. The crude protein and fiber contents of the flour fractions increased (55.27–65.92% and 3.21–3.98%, respectively) with increase in wheel speed from 20 to 35 Hz. Furthermore, the protein solubility increased with increases in wheel speed and all the flour fractions had significantly (p < 0.05) higher values (57–81%) than the CTL (42%) at pH 7. The oil droplet sizes of emulsions made with fine flour fractions were significantly (p < 0.05) lower when compared with equivalent coarse fractions and the CTL across all pH values. For each wheel speed, water holding capacity values of the coarse fractions (1.69 g/g) and CTL (1.65 g/g) were significantly (p < 0.05) higher than those of the fine fractions (0.62–0.71 g/g). In contrast, the fine flour fractions had significantly (p < 0.05) higher oil holding capacity (0.99–1.09 g/g) and protein digestibility values (77.61–79.33%) than the coarse flours (0.49–0.56 g/g and 76.16–77.88%, respectively) and CTL (0.69 g/g and 73.63%, respectively). Least gelation concentration of the coarse flour fractions decreased from 9% for the 20 Hz air classier wheel speed to 5% for 30 Hz while those of the fine flours did not change (7%). The starch digestibility profile, trypsin-chymotrypsin inhibitors, total phenolic, and total flavonoid showed significant differences with the fine fraction exhibiting superiority when compared to the coarse fraction. We conclude that air classification could be used to obtain fava bean protein fractions with specific properties for use as ingredients for the formulation of various food products.