ABSTRACT
Starch was isolated from three different barleys with normal, highamylose, or high-amylopectin (waxy) starch. The laboratory-scale starch isolation procedure included crushing of grains, steeping, wet milling, and sequential filtration and washing with water and alkali, respectively. Yield and content of starch, protein, and dietary fiber, including β-glucan, were analyzed in isolated starch and in the by-products obtained. Starch yield was 25–34%, and this fraction contained 96% starch, 0.2–0.3% protein, and 0.1% ash. Most of the remaining starch was found in the coarse material removed by filtration after wet milling, especially for the high-amylose barley, and in the starch tailings. Microscopy studies showed that isolated starch contained mostly A-granules and the starch tailings contained mostly B-granules. Protein concentration was highest in the alkali-soluble fraction (54%), whereas dietary fiber concentration was highest in the material removed by filtration after alkali treatment for the normal and waxy barleys (55%). The β-glucan content was especially high for the waxy barley in this fraction (26%). The study thus showed that it was possible to enrich chemical constituents in the by-products but that there were large differences between barleys. This result indicates a need for modifications in the isolation procedures for different barleys to obtain high yields of starch and different by-products. Valuable by-products enriched in β-glucan or protein, for example, may render starch production more profitable.
