Increased grain density of spring barley (Hordeum vulgare L.) is associated with an increase in grain nitrogen

Barley for malting is evaluated by different grain quality measures, one of these measures is specific weight. An increased specific weight is assumed to lead to higher malt output, however this has not yet been proven. Specific weight is a measure of bulk density, a combination of both individual grain density and the packing efficiency of the grain. Links between specific weight or its components to aspects which may affect malt output have not been investigated. Here we examined correlations between barley grain density and nitrogen content, carbon content, starch content, amylose/amylopectin ratio and starch granule metrics. We show that nitrogen content and the proportional volume, number and surface area of starch B-granules positively correlated with grain
density. An equation was built to predict grain density from grain nitrogen and the proportional volume of starch B-granules; this described 47% of observed variation in grain density. An independent validation of the equation indicated that nitrogen content alone was sufficient to successfully estimate grain density. As nitrogen content is consistently positively correlated with grain density and hence specific weight, a high specific weight could be unfavourable for some malting end-uses which require low grain nitrogen. Achievement of high specific weight must therefore carefully consider end-user requirements.