Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/1997
Publication Date: N/A
Interpretive Summary: Oat bran is a product produced from oat groats by any of a variety of dry milling processes. By definition, oat bran is enriched in the soluble fiber component, beta-glucan, which is responsible for cholesterol lowering effects associated with oat bran products. In order to develop new oat cultivars with improved bran characteristics, we have developed a laboratory scale procedure for milling oats to produce bran comparable to commercially available products. We found that either hammer-milling or roller milling, followed by sieving, produced oat brans highly enriched in beta-glucan, protein and ash. Tempering the groats, by adding defined amounts of water 20 minutes before milling, significantly improves bran yields. Further processing of our oat brans with a laboratory bran finisher significantly increased the beta-glucan and protein concentrations in the bran to levels significantly greater than those customarily found in commercial oat brans. Because wheat bran is primarily derived from the outermost layers of the wheat kernel, we tested the utility of a pearling mill, which abrades off the outside of grains, to produce an oat bran. The oat bran produced from a pearling mill contained much less beta-glucan and protein than did roller mill or hammer mill derived brans, indicating that these oat brans are not derived from the outermost layers of the oat groat. Instead, they appear to be a concentration of the cell from throughout the oat groat, to which much of the protein in the groat adheres. The pearling isolated the outer layers directly, but because it was low beta-glucan concentration, it did not meet the official definition of oat bran.
Technical Abstract: Three mechanisms of oat milling were tested for laboratory scale oat bran production. Oat bran consistent with commercially obtained product was generated with either roller milling or impact milling of groats, followed by sieving to retain larger particles. These bran preparations were enriched about 1.7-fold in beta-glucan and ash, 1.4-fold enriched in protein, and 1.1-fold enriched in lipid. Bran finishing made further enrichments in protein, beta-glucan, and ash. Tempering oat (to 12% moisture for 20 min) improved bran yield from roller-milling nearly two-fold, but had little effect on bran composition. Bran yield from the impact-type mill was significantly affected by grinding screen size. Oat bran obtained from a pearling mill was only slightly enriched in beta-glucan and protein, but more heavily enriched in ash and oil than brans from roller or impact mills. We concluded that sieving after roller and impact milling does not isolate the outer layers of the oat groat, as is the case for wheat milling, but concentrates a cell wall fraction, to which protein and ash will adhere. The pearling mill isolated the outer layers of the kernels directly, but because of its low beta-glucan composition, did not meet the AACC definition of oat bran.