Impact of Lactic Acid Bacteria on Sour India Pale Ale (IPA) Fermentation: Growth Dynamics, Acidification, and Flavor Modulation

Sour beer production is strongly influenced by the choice of lactic acid bacteria (LAB), yet few studies have systematically compared strain-specific contributions under controlled kettle souring conditions. This study evaluated the fermentation performance and flavor-modulating potential of three LAB species—Lacticaseibacillus paracasei, Pediococcus pentosaceus, and Leuconostoc mesenteroides—in sour India Pale Ale (IPA) brewing. Growing assessments showed that P. pentosaceus exhibited the most rapid and stable proliferation, while L. mesenteroides required a longer adaptation period. Acidification trials demonstrated that L. paracasei achieved the lowest pH (3.26–3.43), contributing to intense sourness, whereas P. pentosaceus and L. mesenteroides yielded milder acidity (pH 3.41–3.65). Gas chromatography-mass spectrometry showed that P. pentosaceus and L. mesenteroides produced significantly higher levels of fruity and floral esters, including 2-pentanol propanoate, which was approximately 4-fold higher than in the control. Principal component analysis further distinguished the beers according to their volatile profiles. These findings highlight the strain-specific potential of LAB in sour beer brewing and provide practical guidance for flavor differentiation in craft beer production.