Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2010
Publication Date: 6/30/2010
Citation: Srinivasan, R., Hicks, K.B., Challa, R.K., Wilson, J., Kurantz, M.J., Moreau, R.A. 2010. Fractionation of barley flour using a combination of sieving and air classification. American Society of Agricultural and Biological Engineers. 53(2):503-508. Interpretive Summary: Our laboratory has been developing winter barley as an energy crop for the Mid Atlantic States. In this region, winter barley can be grown on winter fallow ground in between rotations of corn and soybeans. This allows farmers to produce 3 crops every 2 years without interrupting the production of food or feed crops. In addition to providing much needed revenue to farmers, winter barley acts as a "cover crop" that prevents excess nutrients and soil sediments from leaching from soils and causing pollution in sensitive waterways, such as the Delaware and Chesapeake Bays. We have worked with breeders to develop superior "energy" cultivars of winter barley that contain desirable characteristics for fuel ethanol production: high starch and protein levels and low levels of non-fermentable carbohydrates. The current phase of our work is to solve remaining technical challenges of converting winter barley grain to fuel ethanol. To do this we have developed new processing technology that aids in conversion of the starch and a similar polysaccharide, beta-glucans into ethanol. In this study, we have used a relatively new process called the Elusieve process to separate our non-fermentable kernel components, like hulls, from the fermentable components, like starchy endosperm. By optimizing the Elusieve process, we have been able to fractionate whole barley kernels into fractions containing higher starch and beta-glucan and lower levels of hulls. The fractions from this process will now be fermented to see if they can be converted to ethanol more efficiently. If ethanol production is improved, the process can be implemented in a new barley ethanol plant that is being built currently in Hopewell Virginia. The successful implementation of the process would help ethanol processors in Virginia and elsewhere to produce ethanol more efficiently and to produce ethanol byproducts such as pelletized hulls for home heating and distillers dried grains with solubles (DDGS) for the regional dairy, swine, and poultry markets.
Technical Abstract: The availability of winter barley in areas of the US that are not well suited to grow corn (such as the Mid Atlantic states), makes it a feedstock of choice for fuel ethanol production in those regions. Recently, it was found that the Elusieve process, the combination of sieving and elutriation (air flow), was effective in fiber separation from corn flour prior to fermentation. The objective of this study was to determine the effect of the Elusieve process on the compositions of fractions from barley flour of hulled as well as hulless barley varieties. The barley grains were milled using a hammer mill and sieved into four size fractions. Air classification of the two largest size fractions using a commercial aspirator resulted in heavier fractions with higher starch, higher beta-glucan and lower neutral detergent fiber (NDF) contents. Elusieve processing was more effective (higher separation factors) for the hulled variety than the hulless variety because higher hull presence caused increased carry over of hull (fiber) into the lighter fractions for the hulled variety. Recently, a new EDGE (enhanced dry grind enzymatic) ethanol process was developed to mitigate the high viscosity problems caused by beta-glucans when barley is used as a fuel ethanol feedstock. In the EDGE process, the enzyme beta-glucosidase is added to liquefied mash to convert the non-fermentable beta-oligosaccharides, which are formed upon partial enzymatic hydrolysis of beta-glucans, to glucose. Glucose is subsequently fermented to ethanol. Elusieve fractionation of barley flour, especially the hulled varieties, could be beneficial in conjunction with the EDGE process, wherein beta-glucans along with starch are converted to ethanol. The increase in beta-glucan and starch contents in barley flour, by hull separation using the combination of sieving and air classification, could increase ethanol productivity.