Starch and Protein Concentration of Pinto Bean Flour by Sieve Fractionation
Abstract
Dry fractionation of pulses typically relies on air-classification. However, this can be a costly investment for small-scale processors. Given this consideration, this study hypothesized that milling and sieving alone could effectively produce high-starch and high-protein fractions of pulse flours, bypassing the need for air classification. Hence, we milled dry pinto beans using a centrifugal mill and then fractionated the flour by sieving through Tyler sieves: 20 mesh (850μm), 30 mesh (600 μm), 40 mesh (425 μm), 50 mesh (300 μm), 60 mesh (250 μm), 70 mesh (212 μm), and 80 mesh (180 μm). We then evaluated the fractions for total protein, total starch, ash, water absorption index (WAI), Oil Absorption Capacity (OAC), and color. The 60-mesh fraction had the greatest starch content amounting to 53.1% and the < 80-mesh fraction had the greatest protein content with a total of 29.77% protein. The high-protein fraction was associated with significantly elevated ash content (4.41%), greater WAI (2.31) and increased OAI (1.75) compared to the whole pinto flour (WPF). The starch fraction had lower ash content (3.54), WAI (1.33), and OAI (1.06). Whiteness (L) of pinto bean fractions increased significantly with fineness, while hue angle and chroma decreased. These results demonstrate that milling and sieving effectively separated pinto bean flour into distinct high-protein and high-starch fractions without the need for air-classification. Such fractions offer potential as pulse flour ingredients with value-added nutritional and functional properties.
Keywords: sieving, milling, fractionation, air-classification, pinto beans
How to Cite:
Simons, C. W., Simsek, S., Young, H. D. & Ciampaglio, C., (2026) “Starch and Protein Concentration of Pinto Bean Flour by Sieve Fractionation”, The Ohio Journal of Science 125(2), 12-19. doi: https://doi.org/10.18061/ojs.6497
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