Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2007
Publication Date: July 20, 2007
Citation: Liu, K. A modified Laboratory Method to Remove Outer Layers from Cereal Grains Using a Barley Pearlier. 2007 Cereal Chemistry. 84(4):407-414. Interpretive Summary: A variety of nutrients, including protein, lipids, vitamins and minerals, and some undesirable components, such as phytic acid, are concentrated in outer layers of cereal grains. For nutritional characterization and end-use exploration, there is a need to develop simple, efficient, and inexpensive laboratory methods in decorticating cereal grains. This would also facilitate experimental production of value-added products, such as concentrated protein ingredients from cereal grains for fish feed. Although equipment such as Japanese Satake rice test mill and Canadian tangential abrasive dehulling device (TADD) have been used for abrading grains in the laboratory, they are relatively expensive and not readily available. This paper describes a comprehensive study on using a Strong-Scott barley pearler, an inexpensive lab equipment, to remove outer layers of cereal grains. After investigation of many factors affecting performance of the equipment and quality of pearled bran and remaining kernel fractions, such as uniformity of pearling and kernel breakage, modifications of the equipment itself as well as the pearling procedure are proposed. The significance of this study is that when the proposed modifications are made, the barley pearler can be used as effective yet inexpensive alternative to Satake rice mill and TADD for abrading various species of cereal grains. The modified method is valuable to cereal chemists, and in particular valuable for our own laboratory to dry fractionate barley and oats in making protein-enriched ingredients for fish feed.
Technical Abstract: A variety of nutrients and some undesirable components are found and possibly concentrated in outer layers of cereal grains. There is a need to develop simple, efficient, and inexpensive laboratory methods in decorticating cereal grains for physicochemical and nutritional characterization and end-use exploration. This study focused on using a Strong-Scott barley pearler (BP) to abrade barleys and investigated factors that could affect kernel breakage, uniformity of abrading, repeatability, and quality of resulting fractions. Results show that the smaller the sample size, the higher the rate of surface removal. The difference in % removal among pearling times decreased as the sample size increased. Screens with smaller holes (larger No. of mesh per inch) decreased abrading efficiency, but reduced kernel breakage significantly. The successive pearling mode (several pearling cycles per sample) not only provided a means to collect different fractions of outer layers and remaining kernels, but also minimized kernel breakage and gave more uniform removal of outer layers among seeds, as compared with the continuous pearling mode (only one pearling cycle per sample). As pearling progressed, the surface color of both outer layer and abraded kernel fractions became whiter. Subsequent trials with several other cereal grains (wheat, rice, sorghum and oats) confirmed above findings. It is concluded that when modifications of equipment and procedures are made, the BP can be used as an efficient and inexpensive alternative for abrading various species of cereal grains.