# Brewing with Unmulated Cereal Adjuncts: Sensory and Analytical Impacts on Beer Quality
## 1 Introduction  
Malted barley is the favoured cereal grain used in traditional brewing processes. Barley is modified during the malting process to ensure biochemical changes occur within the grain which generate essential enzymes, sugars and proteins required in the production of worn [1]. Malted barley forms the base grist material for most beers, however, the partial substitution of barley with cereal adjuncts such as wheat, corn and rice is well established in the brewing industry. Malting is an energy intensive process and brewing with a proportion of unmulated adjuncts has become an attractive option for cost and carbon footprint reduction. The malting process accounts for 217 kg CO\({}_{2}\)eq/t, which is nearly half of the total carbon footprint incurred during malt production, with the agriculture of malting barley accounting for the additional 241 kg CO\({}_{2}\)eq/t [2]. Therefore, utilising unmulated adjuncts can considerably reduce the carbon footprint of the malting and brewing chain. Global climate change is predicted to have important consequences for barley production. Crop and economic models have forecasts that extreme weather events may cause substantial decreases in barley yields worldwide with a potential 17% loss under the most severe conditions [3]. Decreases in the global supply of barley could lead to increasing beer prices with a 193% increase in price by 2099 according to some projections [3]. Employing a range of adjunct materials may therefore play a role in securing raw materials supply for brewing through a period of projected climate change. For example, it has been predictedthat climate change will not have significant negative effects on maize yields in the US and China [4]. Unmalted adjuncts are often employed in the brewing industry as an alternative cost-efficient source of extract, as well as for the individual functionality they bring to the brewing process and finished beers. Cost reductions can be driven by minimising the requirement for the malting process and its related costs [5]. Additionally, cost savings can arise from replacing potentially expensive barley malt with cheaper locally sourced grains. The choice of unmalted grains across the global industry is thus heavily influenced by local raw materials supply and cost considerations. Barley and corn are the most commonly used adjuncts in Europe and America, whilst rice usage is popular in Asia [5; 6]. The quality attributes of some of the world's leading global beer brands are based on adjuncts used in their recipes. Adjuncts are utilised by brewers both to modify beer quality (e.g., flavour, foam, colloidal stability) and to enable production of new innovative products with specific desired features [5]. Brewing with unmalted cereal adjuncts, particularly at higher concentrations, can be challenging and a more detailed understanding is required about the factors which limit the upwards incorporation rates of unmalted adjunct materials. When introducing high concentrations of adjunct material, the functionality and processability of the grist must be assured, and there should be no negative impacts on production or product quality. The main disadvantage in terms of processability when including unmalted adjuncts is the decrease in amylolytic, cytolytic and proteolytic enzymatic activities in the grist, as these enzyme systems are activated and synthesised during the malting process [7]. The actions of these three enzyme systems during malting and mashing influences the chemical composition of word and the efficiency of brewing extract recovery [7]. The varied biochemical composition of cereal materials will have impacts both on the brewing process performance and on finished beer quality. A deficiency of enzyme activity and variations in composition of unmalted adjuncts can consequently impact the flavour profile of adjunct beers [6; 8]. However, such impacts to the aroma and flavour of the finished beer are still not fully understood.