Duplex digital PCR for the determination of meat proportions of sausages containing meat from chicken, turkey, horse, cow, pig and sheep

The probability of accidental or intentional addition of another species of meat in meat products is high. Meat is expensive and in the context of food waste, it is reasonable to reduce loss of this precious material during the production. However, the line between fraud and waste reduction is thin. Minor variations, e.g., up to 1% of unexpected meat content, may be tolerated. But to distinguish between minor variations and severe deviations to the list of ingredients, analytical methods with a low measurement uncertainty are required. The recent introduction of digital PCR indicated that this new method may lead to a reduction of the measurement uncertainty. We present the measurement of proportions of beef, pork, chicken, turkey, sheep and horse meat in a cooked sausage matrix and a procedure to calculate the proportions (w/w) based on target DNA concentrations measured using droplet digital PCR. Six laboratories applied these methods and determined the w/w proportions of 20 sausage samples. It was shown that these methods in conjunction with conversion factors can be used to estimate meat proportions in mixed meat products with superior accuracy and precision compared to results generated by real-time PCR.