Predicting Alcohol Yield from UK Soft Winter Wheat for Grain Distilling: Combined Influence of Hardness and Nitrogen Measurements

ABSTRACT The work reported in this paper showed that whilst grain nitrogen is a key player in determining the alcohol yield obtained from soft winter wheat, other parameters such as grain hardness may also be important. A strong positive correlation was found between grain hardness and grain nitrogen and both parameters affected alcohol yield of processed wheat in a similar way. Although an inverse relationship between alcohol yield and grain nitrogen was observed at each of four growing sites, this relationship was stronger for wheat grown at moderate nitrogen sites than at higher or lower nitrogen sites. A similar inverse relationship, comparable to that obtained for nitrogen, was also found between alcohol yield and grain hardness. Further statistical analysis showed that an improved prediction of alcohol yield can be obtained based on measures of both hardness and total nitrogen, as opposed to total nitrogen alone. Residue viscosity did not appear to directly influence alcohol yield. However, some correlation was observed between both grain nitrogen and hardness and residue viscosity at certain sites. While correlation between nitrogen and residue viscosity was observed at the site with the highest nitrogen content, correlation between hardness and residue viscosity was observed at the two sites where nitrogen content was highest. Finally, scanning electron microscopy revealed that very high protein content was found to result in deformation of the starch structure, limiting access of starch during processing and lowering alcohol yield.