Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2011
Publication Date: 4/25/2012
Citation: Srinivasan, R., Hicks, K.B., Wilson, J., Challa, R.K. 2012. Effect of barley roller milling on fractionation of flour using sieving and air classification. Applied Engineering in Agriculture. 28(2):225-230. Interpretive Summary: Barley is a grain that is currently being considered as a new feedstock for making new advanced biofuels, such as fuel ethanol. Most varieties of barley contain a hull made up of non-fermentable lignocellulosic biomass that covers and protects the starch-rich endosperm part of the kernel. If ethanol producers use the entire kernel, hull and endosperm to make ethanol, the presence of the hull does nothing to produce ethanol, but it decreases the efficiency of the system by taking up fermentor space and increasing the energy needed to stir and transport the “mash”. We have developed a new two step method to remove the hull from barley before it is used to make fuel ethanol. In this new process, barley kernels are passed through the same type of “roller mills” that are used to convert wheat into flour. The barley flour so produced is then treated with a new Elusieve process, which separates out the unwanted barley hull using a combined sieving and air-classification (density) process. The process resulted in a barley flour much improved for ethanol feedstock over traditionally ground barley. The study also revealed a roller milling process that produced improved barley flour without having to use the Elusieve process. This information will be useful to future barley ethanol plants operators who will use the process to improve plant efficiency and profitability.
Technical Abstract: Separation of hulls prior to fermentation of barley flour could increase fuel ethanol productivity and the hulls would be an additional coproduct. In a recent study, it was found that the Elusieve process, a combination of sieving and elutriation (air classification) was effective in separating hulls from flour produced by hammer milling of a hulled barley variety “Thoroughbred”. Roller milling is another common method used for producing flour from grains. The objectives of this work were: 1) to study the effect of roller milling on the efficacy of sieving and air classification for fractionation of Thoroughbred barley flour, and 2) to study the effect of roller milling parameters such as the gap between rollers and number of corrugations per inch in rollers on fractionation. Sieving and air classification were effective for hull separation from roller milled flours. The increase in starch content from 59.6% in the original flour to 62.1 - 65.4% in the enhanced flour would increase productivity of fuel ethanol from barley. Loss of starch into the fiber product was low: 0.8% to 1.1%. In the cases where barley was milled using an additional set of rolls that had high number of corrugations per inch, air classification was not needed (sieving alone was sufficient) for producing the enhanced flour. In the cases where either only one set of rolls were used or where the additional set of rolls had low number of corrugations per inch, air classification was needed for producing the enhanced flour.