Insights into the Foaming Properties of Alcoholic and Non-Alcoholic Beers Using Four Different Foaming Methods

Although foam is an important quality parameter of beer, the foam of non-alcoholic beers (NABs) often fails to meet consumer expectations. Because scientific insight into the topic is lacking, this study investigated the differences in foaming properties between NABs and corresponding alcoholic beers (ABs), focusing on the underlying destabilisation mechanisms and associated physicochemical properties. The foam properties of 16 commercial beers were investigated using four foaming methods, including a novel method that allows for foam replenishment. By generating foams with varying (initial) volume, liquid content and lifespan, each test highlighted distinct destabilisation mechanisms and, when combined, offered a more complete understanding of foaming properties. The results confirm that NABs produced by dealcoholisation exhibit significantly reduced foam capacity and stability, resulting in a coarser foam structure compared to ABs. This instability was primarily attributed to a higher rate of coalescence, potentially driven by lower alcohol content and higher surface tension. NABs produced using alternative fermentation exhibited significantly better foam stability than those produced by dealcoholisation, highlighting the possible influence of the NAB production technique. This work provides fundamental knowledge necessary for brewers to create targeted strategies aimed at improving the foam quality of NABs.