PCR

PCR, the polymerase chain reaction, is a method for amplifying specific DNA sequences using two short oligonucleotide primers that flank the target region and bind opposite strands. Repeated thermal cycles of denaturation, primer annealing, and strand extension with heat-stable polymerases double the DNA each round, producing exponential amplification from even trace starting material. In food testing, PCR detects pathogens, allergens, species adulteration, and genetically modified ingredients with exceptional sensitivity and speed. Real-time variants quantify targets for enumeration. Primer design, contamination control, and validation determine reliability. PCR has revolutionized food microbiology, compressing detection from days of culture into hours.