CHAPTER 11. Optical and Acoustic Label-free Instrumentation for Molecular Detection with a Focus on Food

In this chapter, we focus on label-free techniques suitable for the detection of analytes in food samples. We demonstrate the capabilities of such techniques on optics-based (surface plasmon resonance, SPR) and acoustic-based (quartz crystal microbalance, QCM) devices using immunoassays. Label-free techniques can be miniaturised and thus can be brought closer to the point of use, such as a farm, a field, a storage space, a shipyard, a factory gate or even a restaurant. First, the working principles of traditional SPR and of a QCM are introduced. The basic terminology is briefly covered and common technical considerations, including the required surface chemistry, limit of detection, ability to multiplex, ability to work with crude samples and complexity of liquid handling, are discussed. Secondly, commercial instruments are described including Biacore, ForteBio and Q-Sense. In addition, newer technical variations such as fibre-optic SPR (FOX diagnostics), imaging SPR (Horiba), multiparametric SPR (BioNavis), and a solidly mounted resonator (BioMensio) are discussed. An overview of different commercialised optic and acoustic label-free techniques and their suitability for food analysis is included. Since most of the instruments on the market focus on more generic assays, the third part of this chapter reviews assays for food analysis that are currently being developed. The fourth and final section provides an outlook on the future of instrumentation in this field.