Rapid Methods for Quality Assurance of Foods: the Next Decade with Polymerase Chain Reaction (PCR)-Based Food Monitoring

Microbiological analysis is an integral part of food quality control, as well as of the management of food chain safety. Microbiological testing of foodstuffs complements the preventive approach to food safety activities based mainly on implementation and application of the concept of Hazard Analysis and Critical Control Points (HACCP). Traditional microbiological methods are powerful but lengthy and cumbersome and therefore not fully compatible with current requirements. Even more, pathogens exist that are fastidious to cultivate or uncultivable at all. Besides immunological tests, molecular methods, specifically those based on polymerase chain reaction (PCR), are available options to meet industry and enforcement needs. The clear advantage of PCR over all other rapid methods is the striking analytical principle that is based on amplification of DNA, a molecule being present in every cell prone to multiply. Just by changing primers and probes, different genomes such as bacteria, viruses or parasites can be detected. A second advantage is the ability to both detect and quantify a biotic contaminant. Some previously identified obstacles of implementation of molecular methods have already been overcome. Technical measures became available that improved robustness of molecular methods, and equipment and biochemicals became much more affordable. Unfortunately, molecular methods suffer from certain drawbacks that hamper their full integration to food safety control. Those encompass a suitable sample pre-treatment especially for a quantitative extraction of bacteria and viruses from solid foods, limited availability of appropriate controls to evaluate the effectiveness of the analytical procedure, the current inability of molecular methods to distinguish DNA from viable cells and DNA from dead or non-cultivable cells, and the slow progress of international harmonisation and standardisation, which limit full acceptance of PCR-based methods in food control. The aim of this review is to describe the context and the prospects of PCR-based methods, as well as trends in research and development aimed at solving the next decade challenges in order to achieve full integration of molecular methods in food safety control.