Quantitative species determination based on real time PCR–Can the results be expressed as weight/weight equivalents?

ABSTRACT Food adulteration is a common challenge in the meat industry. Polymerase chain reaction (PCR) has been used as a method to detect contamination from different species of meat. From a consumer perspective, a PCR method with measurements in terms of weight/weight (w/w) ratios will be more familiar. In this study, the focus was on how to convert the results of quantitative analysis from genome/genome (g/g) to w/w using real-time PCR. The mixtures with different ratios of mutton in pork were analyzed as test samples. The c values of different species, as a reflection of the key conversion factors, were established and evaluated. The effects of heat treatment on w/w conversion of PCR data were also assessed. The results indicated that the c value shows significant variability among individual samples. An average c value was found to cause a bias of more than 7% for mixtures in the range of 20–80%. For individual meat samples with pre-determined c-values, real-time PCR was useful for quantitative analysis of mutton contamination in pork within the range of 20–80%, with a bias of detection of less than 2%. However, this method was shown to have a limit of quantification of 5% with mutton in pork. Furthermore, heat treatment (121°C, 15 min) significantly reduced the accuracy of quantitative analyses. Because the c value is not available for most commercial samples, and some food products are subjected to heat treatment as a method of sterilization, accurate quantitative analysis (w/w) may not be an option for commercial samples using PCR-based technology.