Food industry biosensors for microbiological safety

Raw meat, milk, seeds and vegetables are the source of bacteria, that are transferred through cross-contamination during food preparation. The standard microbiology method in food pathogens detection is the colony counting on agar plate, a procedure that requires several days for revealing the presence of a pathogen. This review will give importance to methods for detection of bacteria in food samples incubated in a pre-enrichment broth for times ranging from 24 to 48 hr, in order to accumulate a sufficient number of bacteria in the exponential growth phase peak. The highest sensitivity in species identification of bacteria has been achieved with molecular methods through amplification of DNA. In addition to the quantitative evaluation of the amplified DNA, DNA biosensors have been developed which are based on the hybridisation of target DNA with highly selective probes bound to a surface. The detection limit of DNA methods range between 10 to 100 colony forming units/ml of sample. Up to now, many biosensor-based methods are labour intensive and cost effective methods, which in addition are difficult to be implemented for in-field application. An ideal biosensor should detect target molecules directly without the use of labelled ligands or multiple washing steps. There are several bottlenecks to be solved in order to perform an efficient analysis. The first is the use of proper surfaces, the second is to efficiently and uniformly print the capture probe (antibody, binding proteins, aptamers) and to have a constant probe density in order to obtain the detection of targets with high reproducibility. The third is to obtain a high sensibility even at a low concentration of the targets. A number of methods are used for the rapid detection of biomolecules in solution. These include immunoassays, chromatographic methods, magnetic and biological biosensor methods (using screen-printed biosensors with immobilized enzymes), and antibody based detection methods. In this review we present an overview on these biosensors , on the imporvements in detection that are comparable to the methods based on DNA amplification (100 colony forming units/ml of sample.).