Evaluation of processing methods of intermediate wheatgrass (Thinopyrum intermedium) for puffed grain & sprouted flour food applications

Abstract

Perennial grains, like intermediate wheatgrass (IWG, Thinopyrum intermedium), are being further explored for their use in human food products and offer environmental advantages. This study evaluated the ability for IWG (‘MN Clearwater’ variety) for use in puffed grain and sprouted flour applications. Two important factors for each objective were selected for study. To investigate objective one, puffed IWG, the gun puffing method was evaluated. Grain moisture content (10, 15, and 20%) and puffing pressure (100, 130, and 160 psi) were evaluated and compared to an unpuffed control. After processing, kernels were analyzed for puffed kernel ratio, bulk density, thousand kernel weight, kernel color analysis, water hydration uptake, water absorption index (WAI) and water solubility index (WSI), as well as damaged or gelatinized starch. Significant changes from puffing were induced on IWG compared to the control. IWG puffed at 160 psi and the control were both imaged using Scanning Electron Microscopy (SEM) to view internal structure. The IWG puffed at a higher pressure resulted in desired properties – a higher expansion ratio, lower bulk density, greater water solubility, lighter kernel color, and more damaged starch. While IWG puffed at a higher moisture content led to a more expanded grain, changes in moisture content had less effect than changes in pressure. Internal structure changes, including an in increase in porosity and kernel size, occurred during puffing and can be seen in the SEM images. To investigate the second objective, sprouted flour, a tray germination method was developed with changes in the germination temperature (10, 15, and 20°C) and germination time (2, 4, and 6 days) then compared to a non-germinated whole IWG flour control. After a germination method was developed and samples were produced, germinated grains were milled into flour. Protein, ash, total starch, and moisture contents were evaluated. Additionally, IWG flours were analyzed using the Micro Visco Amylo-Graph (MVAG) for cook pasting properties. Germination had a significant impact on the quality of the sprouted flours. A longer germination time and a higher germination temperature led to an expedited reduction in the quality of IWG germinated flour. This study improves our understanding of opportunities IWG as a product in the food industry and is paramount for companies looking to add a ready-to-eat puffed or sprouted flour perennial grain to the product offerings and formulations.