Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2007
Publication Date: 7/20/2007
Citation: Liu, K. 2007. Laboratory Methods to Remove Surface Layers from Cereal Grains Using a Seed Scarifier and comparison with a barley pearler.. Cereal Chemistry.84(4):407-414
Interpretive Summary: Distribution of a variety of nutrients, including protein, lipids, vitamins and minerals, and some undesirable components, such as phytic acid, within a cereal grain are heterogeneous, and many of the valuable nutrients are located in the outer layers. Efficient and reliable laboratory methods to remove these layers will allow for the 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. In a separate report, a Strong-Scott barley pearler (BP) was investigated in our lab for abrading cereal grains and obtaining outer layer fractions and abraded kernels. This study was the first one to comprehensively investigate electrical seed scarifier (SS), another very inexpensive table-top abrasive dehulling device, for removing layers from cereal grains. After examining many factors that affected abrading performance and quality of abraded products, and comparing with the barley pearler, a new procedure, along with suggested modification of the equipment, is proposed. The significance of this study is two-fold. First, it showed that the SS can be an inexpensive, versatile, yet efficient and reliable alternative for abrading various species of cereal grains. Second, it also showed that the SS is easier to operate, produces more repeatable data, and gives more uniform removal within a seed compared to the barley pearler. The new method, in combination of equipment modification, 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: The distribution of nutrients and undesirable components within a cereal seed is heterogeneous, and many of the valuable nutrients are located in the outer layers. Efficient laboratory methods to remove these layers will allow for the experimental production of value-added products. A seed scarifer (SS) was used to abrade barleys and factors affecting abrading performance and the quality of end fractions, including sample charge size, mode of operation, motor speed and cereal species, were investigated. Results showed that the level of surface removal decreased as the sample charge size increased. Compared to a continuous abrading mode (only one abrading cycle per sample), a successive abrading mode (multiple abrading 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. Reduction in motor speeds tended to decrease removal efficiency, but significantly prevented kernels from breakage. Subsequent trials with other grain species (wheat, rice, sorghum and oat) confirmed above findings. Compared to a barley pearler, the SS was easier to operate, produced more repeatable data, and gave more uniform removal from a seed. The SS is an inexpensive and reliable alternative for abrading various species of cereal grains.