Spontaneous fermentation of Tunisian dromedary milk: VASE™-GC-MS volatile profiling, physicochemical and mineral composition, bioactivities, and lactic acid bacteria enumeration

Fermented dromedary camel milk is a traditional food in arid and semi-arid regions, yet the kinetics of spontaneous fermentation remain insufficiently characterized, particularly for Tunisian milk. This study investigated the 72 h spontaneous fermentation of raw Tunisian dromedary milk using an integrated kinetic approach combining physicochemical, compositional, microbiological, and bioactivity analyses.

Raw milk was incubated at 37 °C without starter culture and sampled at 0, 12, 24, 48, and 72 h in three independent biological replicates. Physicochemical parameters, mineral composition, sugars, organic acids, volatile compounds by VASE™-GC-MS, fatty acids, lactic acid bacteria (LAB) counts, antioxidant activity, and antimicrobial activity were evaluated.

Fermentation induced progressive acidification, as reflected by a decrease in pH and an increase in titratable acidity, together with increased viscosity and reduced water activity. Total solids and protein content decreased slightly, whereas fat and ash contents remained relatively stable. Sodium and magnesium concentrations increased during fermentation, while calcium and potassium decreased and iron remained stable. Lactose consumption was accompanied by the accumulation of lactic and succinic acids, which is consistent with active microbial metabolism. VASE™-GC-MS analysis revealed time-dependent changes in the volatile profile throughout fermentation. The lipid fraction remained dominated by long-chain fatty acids, mainly C16C18. LAB counts increased from 4.30 to 8.77 log CFU mL^-1, while antioxidant and antimicrobial activities were significantly enhanced over time.

Overall, spontaneous fermentation improved the technofunctional, antioxidant and antimicrobial properties, highlighting its potential as a traditional functional food.