Abstract
Foam retention is a key beer quality attribute influenced by malt proteins, hop acids, carbonation, alcohol content, and colloidal interactions. This study examines foam retention improvement through balanced malt protein and hop acid composition. Model beers were produced with different malt protein levels and hop-derived bittering profiles under controlled brewing and conditioning conditions. Foam height, foam half-life, bubble size distribution, surface tension, protein concentration, iso-alpha acid level, turbidity, pH, and sensory mouthfeel were evaluated. The results show that moderate protein fractions improved foam film strength, while hop acids enhanced foam persistence by supporting interfacial stability. Excessive protein increased haze risk, and excessive hop acid addition caused harsh bitterness without proportional foam improvement. The best foam retention occurred when malt protein and hop acid levels were balanced with stable carbonation and low oxygen exposure. The study demonstrates that foam quality depends on coordinated colloidal balance rather than isolated adjustment of malt or hop components.