Interaction Between Iso-α-Acid Extracted from Hops and Protein Z Improves Beer Foam Quality and Stability

Foam quality is an important index for judging the quality of beer. In this experiment, the interaction between PZ and iso-α-acid extracted from hops and its effect on beer foam production were investigated. According to the results of fluorescence titration experiments, the stoichiometric number ratio of PZ interacting with iso-α-acid was 3.91 ± 0.39, and the binding constant K was (2.16 ± 0.23) × 105 M−1. According to the results of molecular dynamics simulations, the binding sites of iso-α-acid in PZ were Leu-396, Ser-292 and Lys-290. The secondary structure of PZ was altered by the addition of iso-α-acid, and the percentage of β-sheets increased from 21.75% to 29.74%. which increased the protein’s flexibility, leading to enhanced foaming, stability, and texture of the foam.