Impact of millet-immobilized probiotic on oxidation and volatile profile of dry-fermented sausage

This study investigated the impact of incorporating millet-immobilized probiotics on the oxidation and volatile profile of dry-fermented sausage. Four formulations were tested: FC (free-cell Lp. plantarum), NI4% (free-cell + 4% millet), I2% (2%-immobilized Lp. plantarum), and I4% (4% millet-immobilized Lp. plantarum). Analyses were carried out during ripening (0, 2, 7, 14, and 21 days) and storage (41, 61, 81, 100, and 121 days). Immobilized probiotics showed higher counts (> 8 log CFU/g) than free cells (P < 0.05) for up to 121 days of storage. Immobilization did not impact the pH, Aw and carbonyl contents of the product, however the millet addition demonstrated a significant antioxidant effect, inhibiting lipid oxidation. Forty-one volatile compounds were identified, with their complexity increasing significantly over time. While alcohols predominated at the onset of ripening (day 0), aldehydes and alcohols became the dominant chemical families during storage. Notably, the volatile profile of treatments with immobilized probiotics (I2% and I4%) remained consistent with the free-cell control (FC), indicating that the millet matrix successfully preserved the product's characteristic aroma. PCA confirmed that sample differentiation was primarily driven by storage duration rather than the immobilization process. Although hexanal was the most abundant oxidation marker, its delayed predominance in millet-immobilized formulations suggests a protective effect against advanced oxidative deterioration. These findings demonstrate that millet is an effective carrier for maintaining probiotic viability and oxidative stability without compromising the volatile fingerprint of dry-fermented sausages.