Caldibacillus thermoamylovorans, the thermophilic bacterium separated from raw milk, would be the crucial spoiler of dairy products

Caldibacillus thermoamylovorans , an emerging thermophilic, spore-forming bacterium, has been increasingly detected in both raw and sterilized milk as well as other dairy products. However, few studies have comprehensively examined its physiological traits and spoilage-associated properties. In this study, C. thermoamylovorans strains were isolated from raw milk samples obtained from northern China, and their biofilm formation, sporulation, thermal resistance, and spoilage potential in milk were systematically evaluated. Specifically, a novel PMA–qPCR assay was established to quantify viable spores after heat treatment, revealing that C. thermoamylovorans exhibits remarkable thermal resistance. Furthermore, contamination of UHT milk with C. thermoamylovorans significantly compromised colloidal stability, accelerated pH reduction, induced off-flavor formation, and reduced shelf life. Analysis of the Turbiscan Stability Index (TSI) further confirmed the detrimental impact of C. thermoamylovorans on the structural stability of milk. These findings highlight the significant risk that C. thermoamylovorans contamination poses to dairy product quality and emphasize the urgent need for more accurate detection methods, more effective sterilization strategies, and comprehensive control measures throughout the dairy production chain to mitigate its negative impact. • C. thermoamylovorans would be the potential spoiler of the UHT dairy products. • C. thermoamylovorans showed the extraordinary heat-resistant ability. • PMA-qPCR assay could accurately quantify the viable spores after heat treatment. • Diverse enzymes produced by C. thermoamylovorans would destroy the dairy stability.