Determining the spirit yield of wheat varieties and variety mixtures

Four winter wheat varieties and the four possible three-component mixtures derived from them were included in a trial in Scotland. The site produced low grain protein levels and there were significant yield and specific weight differences between varieties. The variety Deben significantly out-yielded the varieties Claire and Riband, both with and without fungicide treatment, but produced grain with significantly lower spirit yield than Claire. Protein contents and thousand corn weights were good predictors of spirit yield in a reference population of wheat samples, but thousand corn weights did not correlate with spirit yield in the trial, as Claire combined small grain with high spirit yield. The relationship between protein and spirit yield was shown to change at lower protein levels and to differ between varieties. Reduction in spirit yield as protein increased was greater in Deben than in a better distilling variety like Consort. A rapid means of predicting spirit yield, based on small-scale measurement of hot water extract and protein content, was devised and a good association between predicted and measured spirit yield was observed in both the reference population and the trial. Mixtures containing cvs. Claire and Deben did not demonstrate the adverse effects on yield and spirit yield observed, respectively, for these varieties, and a mixture comprising cvs. Claire, Consort and Deben significantly out-yielded Claire and gave higher spirit yields than Deben. These benefits, together with the potential yield stability and disease reduction characteristics of wheat mixtures, make them a viable commercial option for distilling.