Progressive Hull Removal from Barley using the Fitzpatrick Comminuting Mill

Abstract

The objective of the study was to explore the use of the Fitzpatrick Comminuting Machine (FitzMill®) to remove the hull from hulled barley while keeping the barley kernel intact, thereby avoiding starch loss. Traditionally, this mill is used to grind material, but we have discovered that it can precisely shear the hull from the kernels using the sharp end of the blades. Different residence times in the mill were compared, and chemical analysis of hull and de-hulled kernel fractions, as well as rates of progressive hull removal, were studied to determine optimal settings. While whole kernels had only about 60% starch content, de-hulled barley kernel fractions had starch contents of over 71%, which are comparable to high-starch grains, such as corn, which are more efficient for fuel ethanol production. Furthermore, corresponding hull fractions contained less than 6% starch which translates to less than 1.5% starch loss from the original kernel. De-hulling will make a significant improvement to the barley's value as a feedstock for fuel ethanol production, increasing the starch content by 11 percentage points, and simultaneously decreasing non-fermentable fractions by a similar level. With a method to fractionate hulled barley into high-starch fractions (de-hulled kernels) and fiber rich hulls, hulled barley becomes a more desirable feedstock for fuel ethanol production. Also, since hulls would be removed prior to ethanol production they would be available for conversion into other valuable coproducts.