Multi-Omics and Chemometric Analysis of Aroma and Shelf Life Dynamics in Raisin Syrup Sourdough and Commercial Yeast Breads

Raisin syrup sourdough is a popular traditional leavening method in Japan, yet its specific impact on bread aroma evolution and shelf life stability remains scientifically underexplored. This study characterized the fermentation dynamics and volatile profiles of raisin syrup sourdough bread compared to a commercial yeast control over a 3-day shelf life, utilizing comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-TOFMS) and primary metabolite profiling of sugars, amino acids, and organic acids. The analysis resolved over 760 volatiles and revealed a fundamental kinetic divergence. While the yeast control exhibited a 24 h metabolic lag, the raisin sourdough achieved rapid activation, establishing a higher initial volatile load immediately post-baking. Driven by lactic acid bacteria dominance and extensive proteolysis, the sourdough's acidic environment facilitated the retention of fruity esters and malty branched-chain aldehydes while effectively suppressing lipid oxidation markers like 9,17-Octadecadienal. Key aromatic markers, including benzenepropanol and Octanoate <isopentyl->, were significantly elevated and stabilized in the sourdough group. These findings demonstrate that raisin syrup fermentation generates a superior, stable aromatic profile, providing a scientific basis for optimizing clean-label artisan bread production in the Japanese market.