Impact of Proteolysis Using Ingredients Other Than Malted Barley on Beer Quality

In recent years, research into sustainable techniques that reduce the environmental footprint of brewing has attracted increasing attention. In particular, brewing beer using adjuncts with a small environmental footprint and ingredients such as un-malted barley, which reduces energy consumption and greenhouse gas emissions during the malting process, are becoming hot topics. However, because these adjuncts have not undergone much starch or protein degradation and contain hardly any enzymes, it is important to use exogenous enzyme preparation to achieve a flavor and appearance similar to that of standard beer. In Japan, due to a unique alcohol tax law that imposes taxes based on the malt ratio of beer ingredients, research into beer brewing using un-malted barley and other adjuncts has been conducted since the 1990s. Kirin Brewery has also developed beer in which some of the malt is replaced with un-malted barley (low-malt beer), and beer in which no malt or barley is used at all, only soybeans and liquid sugar (non-malt beer). In this presentation, I review the technologies we have developed to achieve a beer-like flavor and appearance. The purpose of using adjuncts is to replace sugar and protein from malt with that from adjuncts. This presentation focuses on protein degradation and reports the impact of the length of the peptide chain on flavor in low-malt beer, as well as the protein-degrading enzymes that affect foam retention in non-malt beer. The issues concerning the flavor of low-malt beer are pungent, sharp, and/or harsh impression (a lack of smoothness and softness). After fractionating and refining the peptides derived from all-malt beer and spiking them into barley beer, we found that high-molecular-weight (HMW) peptides (10–20 kDa) had a significant effect on improving smoothness and softness, demonstrating that it is possible to improve the smoothness and softness of low-malt beer by increasing the content of these malt-derived HMW peptides. We also developed a separate mashing method in which malt and barley saccharification are carried out separately to limit excessive degradation of malt-derived HMW peptides. In addition, despite containing the same proportion of amino acids, non-malt beer has a lower foam retention time than all-malt beer. After fractionating and identifying a protease preparation and evaluating its effects on foam retention, we found that the alkaline protease (ALP) contained in the protease preparation helped reduce foam retention, demonstrating that it is possible to improve the foam retention of non-malt beer by using an enzyme preparation that contains almost no ALP. Although, un-malted barley and soybeans may not necessarily be the adjuncts on which brewers should focus to reduce environmental footprints and improve sustainability, we believe that these findings can be applied to brewing with other adjuncts and may be of help to the beer industry.