Roasted Malt for Distilling: Impact on Malt Whisky New Make Spirit Production and Aroma Volatile Development

Abstract

Scotch malt whisky is typically produced using lightly kilned malted barley that imparts a relatively subtle aroma to the final product. Recently, there has been increased interest in exploring the feasibility of using roasted malts during whisky production to control congener profile. Although roasted malts are used widely within the brewing industry to develop product color and aroma in beer, applications and challenges have not yet been established for whisky production. This study investigated a role for roasted malt as a tool to impact whisky volatile composition and the consequences of such use for production efficiency of whisky new make spirit. Pot still malt was roasted at laboratory scale (0–60 min at 80–220 °C) and incorporated into a grist (≤50% w/w) for production of new make spirit. The influence of roasting conditions on malt processing characteristics and the impact on the concentration of key roasted malt volatile compounds in distillate were assessed using response surface modelling. Concentration of aroma active pyrazines and furans increased in the distillate produced using roasted malts (particularly when using malt heated >150 °C). Key indicators of process efficiency such as wort fermentability and alcohol yield reduced as intensity of malt roasting increased. Process efficiency when using low proportions of roasted malt (10% w/w) was comparable to that when using only pot still malt, but distillate volatile profile still differed significantly.