Nanosensors for improved safety and quality in milk
Members of the 'Development of nanosensors for the detection of quality parameters along the food chain' (NANODETECT) project plan to develop highly sensitive and specific nanosensor systems for rapidly detecting contaminants and assessing their minimal risk level (MRL) without using harmful solvents. For milk quality control, the detection parameters used were contaminants such as aflatoxin M1 (AFM1), drug residues and fraud (blending goat milk with cheaper cow milk). Researchers selected SU-8 (epoxy-based light-sensitive material) for coating the polymethylmethacrylate (PMMA) surface using photolithography for patterning microstructures. Fluorescent dyes phycoerythrin (PE) or Alexa 532 were chosen for labelling. Biological detection systems for AFM1, drug residues and milk quality were designed using enzyme-linked immunosorbent assay (ELISA) or competitive assay formats. Researchers produced monoclonal antibodies for AFM1 detection, milk purity assessment and drug residue testing. Specifications for fluorescence immunoassays (FIAs), sample volumes, microstructures and more were optimised for better specificity and sensitivity before prototype development using tuberculin-tested (TT) milk. In order to reduce dead volume, this prototype design was modified after testing to include the addition of bubble traps and serial continuous flow paths. The final NANODETECT device included an optical sensor, pump system, temperature sensor, and microfluidic devices with application-specific fluidic connections and stepper motor (linear stage) for positioning. Acrylonitrile butadiene styrene (ABS) casing was used for robustness and opacity to light. System data and measurement were controlled by a computerised touch screen with an interactive graphical user interface (GUI) and Linux operating system. A decision support system (DSS) was built using Microsoft's .NET4 and ClickOnce software for data importing, calibration, comparison and reporting. This system was tested by two SMEs for sensitivity and reliability in quality assurance using powdered milk, milk standards or pasteurised milk, with promising outcomes. To validate results, Spanish herds' raw milk samples were first characterised for pH, fat, protein and more. Standard operation procedures (SOPs) were developed for quality control and assurance. The milk samples were contaminated or blended with other substances and analysed using existing commercial technologies and the NANODETECT device. For the validation of results, liquid chromatography–mass spectrometry (LC-MS/MS) and Luminex MAGPIX systems were used. NANODETECT project outcomes were promising. Device exploitation in food quality control will provide state-of-the-art systems that are user friendly, rapid, economical and environment friendly.
