Optimised dry processing of protein concentrates from Australian pulses: A comparative study of faba bean, yellow pea and red lentil seed material

Milling and air classification settings were optimised for production of protein concentrates from Australian faba bean, yellow pea and red lentil seed material. Pulses were milled to flour of three progressively finer particle size distributions (D₅₀ of 23–25, 16–18 and 13–14 μm) and air classified at classifier wheel speeds of 7080, 9600 and 10,200 rpm. Maximum protein concentration was reported for pulse flours (D₅₀ of 13–14 μm) at 9600 rpm. Protein concentrations of 61.4, 58.1 and 61.0 g/100 g (db.), reflecting a fold increase in protein content of 1.9, 2.3 and 2.1, were reported for faba bean, yellow pea and red lentil, respectively. Protein, ash, fat and total dietary fibre contents were significantly higher in fine fractions (p < 0.05), compared with coarse fractions, resulting in protein concentrates with enhanced nutritional properties. Amino acid score (AAS) of protein concentrates highlighted deficiencies in sulphur-containing amino acids, methionine and cysteine (MET + CYS), and tryptophan. Based on the lowest AAS (MET + CYS), protein concentrates were ranked highest for yellow pea (0.75), followed by faba bean (0.58) and red lentil (0.51). Phytochemical analysis demonstrated that bioactive constituents also co-concentrated with protein (fine fraction), potentially leading to protein concentrates with enhanced health benefits. Shelf-life assessment for the original flours and protein concentrates indicated the onset of rancidity after 3 months of storage. As fat content co-concentrated with protein, the rancidity (%) scores were higher for protein concentrates compared with the original flours. This demonstrates the importance of developing effective treatments, suitable for dry processing, which can extend shelf-life and stability of protein concentrate ingredients for domestic and export markets. The objective of this study was to increase the knowledge available on dry processing of protein concentrates from Australian pulses. The information generated from this study will look to inform future commercial scale processing operations.