21 - Biosensors for process monitoring and quality assurance in the food industry

Abstract

The availability of high-quality food with respect to nutrition, freshness and food safety is a major issue for customers and legal authorities. As a consequence, food has to be chemically analyzed for a number of compounds which are indicative for the parameters mentioned above. Analyses have to be carried out upon delivery of raw material at a food-producing company, during the process of food production, and prior to delivering the product to a customer. As an alternative to classical analytical methods, in the past biochemical analytical methods were established. Of these enzyme assays are probably the best known, and a number of immunoassays (ELISAs) are available. These methods offer the advantage of reduced sample pretreatment due to the specificity of the biochemical reaction involved. Further research led to the introduction of the biosensor concept, which differs from enzyme or immunoassays by the immobilization of one reaction partner, its reusability for a number of assays, and often a high degree of automation of the whole analytical procedure. As there already exist review articles on enzyme-based biosensors for food analysis (e.g. Warsinke, 1997, Luong et al., 1997) as well as commercially available sensor systems which allow the determination of food constituents such as sugars, alcohols and organic acids (see Chapters 22 and 23 in this book), we focus in this chapter on biosensor systems for the detection of various food contaminants. These food contaminants may originate from plants or animals themselves by their prior treatment with e.g. pesticides, antibiotics, hormonal anabolic agents or from microbial infection leading to the presence of pathogenic bacteria (e.g. Salmonella), bacterial toxins (e.g. Staphylococcal enterotoxins or Shiga-like toxins), or mycotoxins. These systems are usually based on the recognition of the analyte by specific antibodies, although some reports exist on the detection of certain classes of pesticides by enzyme inhibition assays (Xavier et al., 2000, Lui et al., 1997). Nowadays, an increasing number of methods are reported based on the detection of genes which indicate either a class of microorganism or which are specific for a certain bacterial toxin. Thus in this chapter, we will first describe the general principles of immunoanalysis, since they are the basis of all 21