Response Surface Methods to Optimise Milling Parameters for Spirit Alcohol Production from Irish Wheat Grain

To standardise research activity and determine alcohol yield from native Irish hard wheat grain, a benchmark approach that reflects Irish industry norms is required. The goal of this study was to optimise milling parameters, grain particle size, and grain to liquid ratio towards developing a standard process. Hard wheat (Triticum avestivum cv. Costello) was used in this study. Experiments utilised a response surface method approach. When both 30 and 35 g of flour were used at a particle size of 0.2 mm, alcohol yield was >350 L of alcohol per tonne of grain (LA/tonne), but with a particle size of 0.65 and 1.1 mm, alcohol yield decreased to between 250 and 300 LA/tonne. It was noted that, during response surface study, >300 LA/tonne was achieved when grain amounts were >25 g, at a particle size of 0.2 mm; therefore, a follow-up experiment was conducted to determine whether there was a significant difference in grain amounts ranging from 25 to 35 g. During this experiment, no significant difference in alcohol yield was observed between 30 and 35 g of grain. Because there were no significant differences, the ideal milling parameters for alcohol yield were determined to be 30 g of flour with a particle size of 0.2 mm, achieving 389.5 LA/tonne. This study concludes that hard wheat can successfully be used for alcohol production, achieving >380 LA/tonne, when a milling size of 0.2 mm and more than 30 g of grain are used, and as such presents an opportunity for its increased use in Irish distilleries.