Effect of Storage and Its Impact on Some Parameters Used in Assessing Distilling Wheat Cultivars

Abstract

Wheat varieties of distilling quality were grown at two locations where different nitrogen fertilizer treatments were administered. Relationships between parameters used to assess wheat quality for Scotch whisky grain distilling such as moisture, nitrogen, hardness, and alcohol yield were assessed after harvest and reassessed after one year to determine the effect storage had on wheat quality. Changes observed in these parameters affected wheat quality in different ways. An increase in average wheat alcohol yield (dry weight basis [dwb]) of 1.6% was found for wheat grown at the lower nitrogen site. These samples had a higher average moisture level at harvest, and showed greater moisture loss (average = 8.7%) during storage. In contrast, a decrease in average wheat alcohol yield (dwb) of 0.6% was observed for wheat grown at the higher nitrogen site. This set of wheat samples had lower moisture levels at harvest, and lower moisture loss (4.1%) after storage. Both sets of wheat showed marginal increases in total nitrogen content which ranged from 0.01�0.12% for lower and 0.01�0.08% higher nitrogen wheat. When the harvest and stored data was compared, weak correlations for oven moisture (R = 0.2766) and grain hardness (R = 0.1789) were found for wheat varieties grown at the lower nitrogen site, while stronger correlations were observed for moisture (R = 0.6573) and hardness (R = 0.8403) for wheat grown at the higher nitrogen site over the same period. The lower nitrogen wheat, which showed a greater loss of moisture during storage, showed a strong correlation for NIR nitrogen (R = 0.9269) compared to wheat grown at the higher nitrogen site (R = 0.7652). Changes observed for moisture, nitrogen, and hardness of stored wheat appeared to have little effect on alcohol yield. Correlation results for alcohol yield assessed before and after storage for lower nitrogen (R = 0.8616) and higher nitrogen wheat (R = 0.8814) were similar and shows that storage did not have a dramatic effect on wheat alcohol yield. This observation has important commercial value because it demonstrates that storage of wheat does not have a detrimental effect on alcohol yield when such wheat is processed for alcohol production.