Flavorful Microbial Fermentation: Metabolic, Flavoromic, and Sensory Analysis Insights Into Probiotic-Enhanced...

This study investigated how fruit matrices and the probiotic strain Lacticaseibacillus paracasei subsp. paracasei F19 (F19) interact with Saccharomyces cerevisiae US-05 to shape volatile formation, microbial viability, and sensory outcomes during the fermentation of Catharina sour beer. The central objective was to fill the current knowledge gap regarding dynamic flavor development in mixed fermentations, particularly in systems where probiotic LAB may contribute both functional and aromatic benefits. Microbial viability was monitored using propidium monoazide quantitative PCR (PMA-qPCR); volatile compounds were profiled by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME/GC-MS); and sensory acceptance was evaluated with 62 untrained panelists using a 9-point hedonic scale. F19 displayed strong viability throughout fermentation (5-7 log CFU/mL), with significant increases after 58 days in the control and passion fruit formulations (p < 0.05), achieving the recommended daily intake level in 350-mL servings. HS-SPME/GC-MS identified 143 volatile compounds, including key aroma contributors, such as 3-methylbutyl acetate, ethyl hexanoate, and ethyl octanoate, as well as 23 core volatiles persistent across all stages. Sensory evaluation revealed a clear preference for the passion fruit beer (6.94 ± 2.01), linked to 18 unique volatiles including 6-methylhept-5-en-2-one and benzaldehyde, while the peach beer-despite containing honey-like 2-phenylacetaldehyde-showed lower acceptance (5.72 ± 1.91). Overall, this first integrated volatilomic, microbial, and sensory analysis demonstrates that L. paracasei F19 enhances aroma diversity and remains viable in fruit-based sour beers, with passion fruit providing the most promising sensory and functional profile for innovative probiotic craft beer development.