The Role of Kettle Souring in Non-alcoholic Beer: Amplifying Hop Flavor Perception and Overall Beer Quality

Non-alcoholic beer (NAB) has grown in popularity due to its lower alcohol content and health benefits, but producing a beer with a desirable flavor profile remains a significant challenge. Kettle souring, a process where lactobacillus bacteria are introduced into the kettle wort to produce lactic acid, has shown promise in enhancing desirable flavor complexity, mitigating unfermented character, and increasing stability in beer.

This study investigates the role of kettle souring in NAB production, focusing on its impact on hop flavor perception, final beer balance, and overall beer quality. Two experiments were conducted utilizing 20hl batches of standardized wort. The first experiment aimed to determine the both individually and in tandem the impact of kettle souring and dry hopping NAB fermented with maltose negative yeast. The wort was split and aliquoted into 1hl vessels with S. cerevisiae variant chevalieri, a natural maltose-negative yeast strain for subsequent fermentation. These fermentations were treated with and without the addition of aromatic hops. The other half of the wort batch was subjected to a kettle souring process prior to fermentation with the same yeast strain and hop treatments. Further bolstering prior findings, the second study investigated the role of kettle souring bacteria compared to a soured pH achieved via lactic acid addition during NAB production. The addition of lactic acid vs lactic acid bacteria was the sole variable in the latter experiment exact in nature to the experimental methods and workflow of the first experiment. The resultant beers were analyzed for sugars and organic acids by HPLC, aromatic compounds by GC, and cutting edge sensory profiles were obtained by trained panelists utilizing QDA.

The results demonstrated that kettle souring, particularly when compared to artificial acidification, led to distinct differences in hop flavor perception, with kettle-soured beers exhibiting more vibrant hop aromas and a balanced flavor profile. Moreover, the pH drop from kettle souring did not produce the same effects as the acidification process, highlighting the unique impact of souring on beer quality. Sensory analysis revealed that beers produced with kettle souring were preferred for their enhanced mouthfeel, greater hop expression, and improved overall flavor stability. Furthermore, the study explored thiol release by the maltose-negative yeast strain compared to standard ale and lager yeasts, revealing its potential to contribute to more complex hop profiles in NABs. This study underscores the potential of kettle souring as a valuable tool for diversifying the flavor profiles of NABs, providing brewers with a method to improve both the sensory appeal and stability of non-alcoholic beers.