Segregation of soft white wheat by density for improved quality

Development of a cost-effective way to segregate soft white wheat (Triticum aestivum L.) by quality would add value to a product that is currently marketed as a low-value commodity. Segregating grain by kernel density for improved quality is a technique that holds promise, but further research is needed. To address this, a study was initiated to determine the relationship of kernel density and soft white wheat quality in terms of test weight, protein content, milling performance, and end-use characteristics. The study was conducted in northeastern Oregon using Stephens soft white winter wheat samples collected from fields representing three different cropping systems over two crop years. Non-separated samples, samples that had been passed over a gravity table once and separated into four density fractions, and samples that had been passed over a gravity table twice and segregated into seven density fractions were analyzed for kernel density and quality characteristics. Correlations between quality characteristics and kernel density ranged from poor to high (r ² = 0.00 to 0.82) for non-segregated samples, but improved as the sample became more homogenous through segregation by density using a gravity table. For the samples that had been passed over a gravity table twice, wheat quality characteristics of test weight, protein content, milling score, mixograph absorption, and cookie diameter were highly correlated with kernel density (r ² = 0.94 to 0.95). Break flour yield was also highly correlated with kernel density (r ² = 0.89). When sets of data for samples that had been passed over the gravity table once and twice were analyzed collectively, correlations between quality characteristics and kernel density were similar, but slightly lower (r ² = 0.88 to 0.94). Quality scores calculated from these data and used to evaluate overall grain, milling, end-use, and overall wheat quality were also highly correlated with kernel density (r ² = 0.91 to 0.96). It was concluded that for homogeneous samples of one variety of soft white wheat, kernel density is an excellent indicator of wheat quality. Additional research is needed to determine if this result extends across multiple cultivars of wheat and additional crop years. Analysis of grain segregated into four density fractions showed that there were significant differences in wheat quality between the lowest density fraction, the highest density fraction, and the non-separated sample. These results further indicate that density segregation is effective for separating wheat by quality and were the impetus for the proposal of a new wheat classification system that uses overall wheat quality as the basis for determining grade. Such a system would provide a marketing advantage since wheat grade would better reflect grain value.