A technique usually shortened to PCR, in which targeted DNA segments are copied millions of times through repeated heating and cooling cycles so they can be detected and analyzed. Food laboratories rely on PCR to identify pathogens such as Salmonella, Listeria, and E. coli in hours rather than days, to verify species in meat and fish and expose substitution fraud, and to detect allergens and genetically modified organisms. Real-time variants quantify the target as well as detecting it. The method’s speed and sensitivity have made it one of the most important tools in modern food safety testing, underpinning rapid release and outbreak response.