Beneficial Effects of Lactobacillus delbrueckii subsp. lactis N102 and Lactobacillus sakei H1-5 Added as Starter Strains on the Metabolome, Safety and Quality of Dry-Fermented Sausages

This study investigated the beneficial effects of individual and co-inoculation with <i>Lactobacillus delbrueckii subsp. lactis</i> N102 and <i>Lactobacillus sakei</i> H1-5 on improving safety parameters, sensory characteristics, and non-volatile metabolite profiles in dry-fermented sausages. Comprehensive analyses were conducted throughout the 20-day maturation period (0, 6, 13, 16, and 20 days), including physicochemical monitoring (moisture content, malondialdehyde (MDA) levels, biogenic amine concentrations, and sodium nitrite residues); sensory evaluation (color parameters and textural properties); and ¹H NMR-based metabolomic profiling. Key findings revealed strain-specific advantages: the N102 inoculation significantly delayed lipid oxidation, achieving the lowest final MDA concentration (4.5 mg/kg) among all groups. Meanwhile, H1-5 supplementation notably improved color attributes (a*/b* ratio = 1.34). The co-inoculation strategy demonstrated synergistic effects through (1) accelerated acidification (pH 5.3 by day 6); (2) enhanced textural properties (significantly increased hardness and elasticity vs. control); (3) optimized water distribution (free water reduced to 0.56% with 64.73% immobilized water); and (4) a significant reduction in sodium nitrite residues (70% decrease) and complete elimination of phenylethylamine (total biogenic amines: 702.94 mg/kg). ¹H NMR metabolomics identified 30 non-volatile metabolites, and the co-inoculation significantly increased the amount of essential amino acids (leucine, isoleucine), flavor-related compounds (glutamic acid, succinic acid), and bioactive substances (gooseberry, creatine). These metabolites enhanced antioxidant capacity, freshness, and nutritional value. Our findings demonstrate that strategic co-cultivation of food-grade lactobacilli can synergistically enhance both the techno-functional properties and biochemical composition of fermented meat products, providing a viable approach for quality optimization in industrial applications.