Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2008
Publication Date: 11/2/2008
Citation: Doehlert, D.C., Ohm, J., Mcmullen, M.S., Riverland, N.R. 2008. Theoretical and Empirical Relationships between Oat Test Weight and Groat Proportion. Cereal Chemistry. Vol 86 (2) 239:246
Interpretive Summary: Value of oats as a commodity is strongly affected by their test weight and groat percentage. The test weight is the weight of a given volume of grain and is controlled by the density of the individual grains of oat and the efficiency with which they pack into the volume. The oat grain is composed of the groat, which is the meaty part that is used for food, and the hull, which is discarded during food production. The groat proportion is the weight of the groat relative to the kernel with the hull. This represents the proportion of the oat grain that can be used for human food. Frequently the test weight and the groat proportion appear to be related to each other, but occasionally they behave quite differently. We have constructed a model that uses oat groat percentage, oat groat density, their hull density, and the packing efficiency of the grain to predict test weight. Over 80% of the variation in test weight could be predicted this model. Our results show why usually test weight varies with groat percentage, and how they can diverge.
Technical Abstract: Test weight and groat proportion are two very important quality characteristics of oat grain. In this study we pose the hypothesis that these two characteristics are related through characteristics of grain density. Test weight is defined as the product of kernel density and packing proportion. Groat proportion, in theory, is the ratio of the groat mass to the kernel mass. We present two theoretical constructions expressing test weight in terms of groat proportion, packing proportion and kernel density components. To test these, we have applied measurements of test weight, groat proportion, kernel density components, and packing proportion of eighteen oat cultivars grown at six environments. Whereas groat proportion alone accounted for only 34% of the variation in test weight, our theoretical constructions that included groat proportion could account for up to 82% of the variation in test weight. Also, we present previously undescribed variation in oat kernel density components across genotypes and environments. Although kernel density alone could account for most of the variation in test weight across genotypes, packing proportion appeared to be more important in describing variation in test weight of a genotype across different environments. We observed significant variation in both groat and hull density, which together with groat proportion, described most of the variation in kernel density.