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

Abstract

Fuel ethanol production from barley is increasing and there is a need to develop more efficient production processes. In the conventional ethanol production process, the hulls (fiber) in barley do not get fermented. The objective of this study is to evaluate a wet fractionation method, similar to the one used in corn wet milling in the endosperm fiber separation step, on the flour remaining after hull separation from barley in order to increase the starch content of barley flour. Hulls were separated from hammer milled barley flour using a combination of sieving and air classification. The remaining flour was soaked in water and the slurry was ground using an attrition mill. The cell wall material was screened out from the fine slurry. The fermentation material produced by hull separation followed by wet fractionation comprised 80.9% by weight of the original flour and contained 10.1% higher starch and 7.9% lower fiber (neutral detergent fiber; NDF) contents than the original flour. The cell wall coproduct has potential as a functional food ingredient because it has high fiber (NDF of 42.7%), high beta-glucan (4.5%) and high protein (20.2%) contents. The increase in starch content may be beneficial in fuel ethanol production.