Comparison of composition and physical properties of soluble and insoluble navy bean flour components after jet-cooking, soaking, and cooking

Authors: Kenar, James - Jim; Felker, Frederick; Singh, Mukti; Byars, Jeffrey; Berhow, Mark; Bowman, Michael; Moser, Jill

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2020
Publication Date: 6/20/2020
Publication URL: https://handle.nal.usda.gov/10113/6996295
Citation: Kenar, J.A., Felker, F.C., Singh, M., Byars, J.A., Berhow, M.A., Bowman, M.J., Moser, J.K. 2020. Comparison of composition and physical properties of soluble and insoluble navy bean flour components after jet-cooking, soaking, and cooking. LWT - Food Science and Technology. 130. Article 109765. https://doi.org/10.1016/j.lwt.2020.109765.
DOI: https://doi.org/10.1016/j.lwt.2020.109765

Interpretive Summary: There is increasing interest and market demand for plant-based protein and dietary fiber, and the nutritional value of pulses (dry beans, peas and lentils) provides a valuable and sustainable source of protein, fiber, and many other functional food components such as antioxidants, phenolics, and prebiotics. Pulse flours are available in the marketplace, but the levels of incorporation into traditional foods is limited by the functional properties of the flours. This study was undertaken to determine how separating navy bean flour into soluble and insoluble components after water extraction at room temperature (23 °C), at standard cooking temperatures (95 °C), or steam jet-cooking (140 °C) would affect the composition and physical properties of the resulting fractions. The distribution of starch, protein, sugar, and many other components was found to vary with treatment temperature, and some of the fractions exhibited enhanced foaming properties and potentially useful levels of soluble protein and prebiotic oligosaccharides. Food processors and consumers will benefit from new ways to utilize pulse flours enabled by readily obtained soluble and insoluble fractions enriched in specific nutritional components.

Technical Abstract: Pulses and their flours represent a valuable source of nutrients such as protein, fiber, and phenolics, among others. However, there are limits to the level of incorporation of pulse flours as replacement for cereal flours in many foods. To enable development of alternative pulse-based food ingredients, this study was undertaken to determine the composition and properties of readily obtained soluble and insoluble fractions of navy bean flour after water extraction at 23 °C, 95 °C, and by excess steam jet-cooking at 140 °C, followed by a single centrifugation. Jet-cooking released nearly half of the flour weight into the soluble fraction as starch was completely dissolved, although some of the protein was apparently denatured and precipitated. Of the three treatments, jet-cooking solubilized the highest proportions of total phenolics (69.2%) and total saponins (58.7 %). The soluble fraction from soaking flour at 23 °C contained no detectable starch, the most soluble protein (42.8 g/100g), and the highest level of raffinose family oligosaccharides (12.4 g/100g). While cooking flour at 95 °C resulted in fractions with mostly intermediate component levels, this may reflect the abundance of swollen starch granules with entrained water recovered in the insoluble fraction. Functional properties (color, water activity, water absorption and solubility, viscosity, and foam capacity and stability) corresponded to the distribution of starch, protein, sugars, and saponins in each fraction. Pasting curves of the soluble fractions and the jet-cooked insoluble fraction were relatively flat, while the insoluble fractions of 23 °C and 95 °C treatments reflected the presence of unswollen and swollen starch granules, respectively. Foam capacity of freeze-dried soluble fractions reconstituted at 3% increased from 289% to 347% with decreasing temperature treatments, however foam stability at 6 h remained high (96.2% and 93.6 % for 140 °C and 95 °C treatments) when soluble starch was present while decreasing to 67.4% for the 23 °C treatment with no soluble starch. These results provide a basis for the development of novel pulse-based food additives with pulse flour fractions differing substantially from raw flour in composition and functional properties.