Fractionation of Barley Flour Using Elusieve Processing: A Combination of Sieving and Air Classification

Abstract

The availability of winter barley in areas of the U.S. 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 air classification (elutriation or aspiration), 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 a hulled (Thoroughbred) and a hulless (Doyce) barley variety. 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. Hulls were preferentially carried into the lighter fractions, as signified by higher NDF contents of lighter fractions. Elusieve processing was more effective (higher separation factors) for the hulled variety than the hulless variety because higher hull presence caused increased carryover of hull into the lighter fractions for the hulled variety. The increase in beta-glucan and starch contents in barley flour, by hull separation using the combination of sieving and air classification, may increase ethanol productivity and may be beneficial in fuel ethanol production from barley when using a process that converts both starch and beta-glucans into fuel ethanol. Since the Elusieve process was most effective only when hulls were present, any dehulling operation prior to grinding would make Elusieve processing needless.

Additional wet milling step for fractionation of barley flour after hull separation

“…A similar trend was also observed by Srinivasan et al (2010). The lighter fractions had higher fiber contents because of preferential carry over of hulls by air.…”

“…lighter fraction yields (higher air velocities) had to be used for smaller sizes because it was visually observed that there were hulls remaining in the heavier fractions when low yields (low air velocities) were used. At higher air velocities, non-hull components also get carried along with hull components (Srinivasan et al, 2010). A similar phenomenon of carry over of non-fiber components at higher air velocities was also observed for distillers dried grains with solubles (DDGS) (Srinivasan et al 2008).…”

“…Each of the four largest sizes, S1 to S4, was air classified using a multi-aspirator (Model VJ8X6, Kice, Wichita, KS) using the procedure described in Srinivasan et al (2010). The multi-aspirator consists of three main componentsda material feeding section, air inlet section, and cyclone section.…”

“…In a recent study, it was found that the Elusieve process, a combination of sieving and elutriation (air classification) can be used to separate hulls from flour prior to fermentation (Srinivasan et al, 2010). Flour produced by hammer milling of barley kernels was sieved into size fractions which were air classified.…”

Pre- and post-treatment enhance the protein enrichment from milling and air classification of legumes

“…For example, the hulls can be removed by air classification (Wu and Nichols, 2005) or by elusieve processing, which is a combination of air classification and sieving (Srinivasan et al, 2010). Hulls are rich in fibre, 91 g/100 g dry matter (Ralet et al, 1993).…”