Rapid detection of trace Salmonella in milk using an effective pretreatment combined with droplet digital polymerase chain reaction

•A pretreatment is proposed based on in situ culture and immunomagnetic separation.•The 25 mL large system is adopted for Immunomagnetic separation.•The pretreatment method with ddPCR could detect 5 CFU/25 mL Salmonella in milk. Salmonella is one of the most dangerous food-borne pathogens around the world to cause a threat to humans and it is urgent to develop the rapid detection method of trace Salmonella in food. Although many advanced techniques have been widely applied to shorten the detection time, the pretreatment method usually used of traditional enrichment and plate culturing to separate Salmonella are complicated and time-consuming. Herein, we developed an effective pretreatment method based on in situ enrichment culture with an immunomagnetic separation step, combined with droplet digital polymerase chain reaction (ddPCR) technology to achieve rapid detection of trace Salmonella in milk, which allowed detecting as low as 10−1 CFU/mL level of Salmonella. It took 8 h to perform the entire testing process from pretreatment to ddPCR detection and analysis. The pretreatment method could be a suitable platform integrating with many detection techniques for the rapid detection of trace Salmonella.