Comparison of properties of raw pulse flours with those of jet-cooked, drum-dried flours

Authors: Felker, Frederick; Kenar, James - Jim; Byars, Jeffrey; Singh, Mukti; Liu, Sean

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2018
Publication Date: 6/11/2018
Citation: Felker, F.C., Kenar, J.A., Byars, J.A., Singh, M., Liu, S.X. 2018. Comparison of properties of raw pulse flours with those of jet-cooked, drum-dried flours. LWT - Food Science and Technology. 96:648-656. https://doi.org/10.1016/j.lwt.2018.06.022.
DOI: https://doi.org/10.1016/j.lwt.2018.06.022

Interpretive Summary: The health benefits of pulses in the diet are well-known, as they are rich in protein, fiber, antioxidants, and many other nutrients. In order to increase the consumption of pulses by a broader range of consumers, methods for modifying the properties of pulse flours are needed to reduce some negative properties and make it easier to incorporate into food applications. Steam jet cooking is a feasible technology for processing starch, and previous studies have identified useful changes in pulse flour properties after steam jet cooking and drum drying. This study was made to investigate whether adjusting the pH of black bean flour slurries before jet cooking could enable further improvements. The results indicate that different flour colors, including pink and violet, could be obtained, as well as specific differences in protein solubility, insoluble fiber content, viscosity, and microstructure. Jet-cooking at low pH levels (3 and 4.5) did not affect antioxidant activity, and at pH 3, some degradation of raffinose family sugars was observed. Steam jet cooking technology can therefore be developed in combination with simple pretreatments to expand the opportunities for creating new food ingredients for different types of foods.

Technical Abstract: Pulse consumption is rapidly increasing due to the growing recognition of the many health benefits that their inclusion in the diet can confer. Pulse flours are becoming more available as they are a convenient starting point for many food applications. One approach for improving pulse flour properties is pretreatment by excess steam jet-cooking, and since black beans are of particular interest due to their conspicuous anthocyanin content and high antioxidant levels, the effect jet-cooking black bean flour at different pH levels from 3.0 to 8.0 was examined. As the pH of jet-cooking increased, water absorption, protein solubility, initial viscosity on pasting, and degradation of phenolics increased. Antioxidant levels were not affected by jet-cooking at pH levels of 3 and 4.5, but decreased 34% and 55% by jet-cooking at pH 6 and pH 8, respectively. At pH 3, raffinose family oligosaccharides were partially degraded and insoluble fiber was reduced. Starch granules were completely dispersed by all treatments and the microstructure of freeze-dried flours when placed in water varied consistently with differences in water absorption and protein solubility. Flours exhibited characteristic bright pink and violet colors when jet-cooked at pH 3 and 4.5, respectively. These results indicate that flours with specific, useful characteristics can be obtained by modifying the pH of flour slurries before steam jet cooking. The results of jet cooking at two different temperatures suggest that further processing modifications and combinations would enable further flour improvement leading to increased utilization in food applications.