The Role of Adjunct Milled Rice, Barley Malt, and different Koji Variations in Alcoholic and Non-Alcoholic Beer Production

Abstract

This study explores the feasibility of using adjunct milled rice in brewing non-alcoholic beer (NAB) traditionally made with barley malt. By substituting barley malt with varying proportions of rice the impact on wort quality and fermentation performance were assessed. Practically, increasing rice content required adjustments, such as adding rice husks for filtration and pre-gelatinising the rice. Despite these modifications, wort characteristics, including original gravity, remained suitable for NAB production. Fermentation with Saccharomycodes ludwigii at 16 °C revealed that higher rice content led to slightly increased alcohol levels (up to 0.45 % v/v when using 100 % rice) within the trials and faster fermentation times (15 days down to 5 days) until a steady ethanol content was reached. Sensory evaluation indicated that higher rice content shifted the flavour profile from “worty” to a more “vanilla” and “buttery” profile. Additionally, Koji (rice inoculated with some species of Aspergillus) was tested as a substitute for barley malt and exogenous purified enzymes. Yellow Koji had higher α-amylase activity, and surpassed white Koji in terms of original gravity and alcohol content. However, Kojionly worts were challenging to filter, suggesting the need for further optimisation. Overall, the integration of adjunct milled rice and Koji offers potential for reducing production time and enhancing flavour profiles in NAB brewing, though practical applications require additional refinement.