From raw grains to aged vinegar: Tracking strontium isotope signatures for provenance assurance in Chinese...

Traditional cereal vinegar production involves complex biochemical transformations, yet their effects on elemental and isotopic compositions remain poorly understood. Here, we investigated the consistency of strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) and the dynamics of mineral elements during solid-state fermentation and aging of Chinese vinegar. Using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), we analyzed Sr isotopes in raw materials (sorghum, Daqu starter, wheat bran, and rice husk) and products from alcoholic fermentation, acetic fermentation, and aging (2-10 years). Results showed a progressive increase in Sr concentrations during fermentation, with significant enrichment during aging (e.g. from 1.52 to 2.78 mg/kg between 3 and 10 years). In contrast, ⁸⁷Sr/⁸⁶Sr ratios remained remarkably stable throughout fermentation (Δ⁸⁷Sr/⁸⁶Sr < 0.0005) and aging (Δ⁸⁷Sr/⁸⁶Sr < 0.0001). These findings demonstrate that Sr isotopic signatures are preserved across all production stages, highlighting their utility as reliable tracers for geographical provenance in traditional fermented foods.