Exploring the mechanisms of flavor formation and polyphenolic changes in hop-infused sourdough bread affected by hop varieties and soaking methods

<i>Humulus lupulus L.</i> (hops) is globally recognized in food production as a flavor enhancer and flour improver. Here, different hop-soaking methods (cold and boiling water) and varieties (Tsingtao and Saaz) were investigated to determine how these influence the flavor profile of hop-based sourdough bread. Headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), ultra-performance liquid chromatography-orbitrap-mass spectrometry, automatic amino acid analysis, and bionic sensors were used to analyze volatile organic compounds (VOCs), amino acids, polyphenols, and sensory attributes. The results showed significant differences in flavor compounds between hop varieties and soaking methods. Cold-water soaked of Tsingtao hops had enhanced aroma intensity, particularly for ketones and aldehydes, while boiling water treatment increased bitter acids and polyphenols in Saaz hops. Pearson and Mantel's tests showed strong correlations between amino acids, VOCs, and polyphenols, with <i>E</i>-nose and E-tongue results aligning closely with sensory scores. These findings provide a theoretical foundation for optimizing hop bread production.