Introdution-Food safety and small molecule detection

Food can transmit disease from person to person by serving as a growth medium for food contaminations that can cause food poisoning. Food safety refers to non-toxic, harmless of food, in line with the nutritional requirements, and does not cause any acute, subacute or chronic hazards on human health. Currently, food safety is a growing concern all over the world especially in developing areas. Ensuring the safety of food has become a significant challenge due to globalization of the food supply and the demand for minimally processed food products. Some potential sources for chemical and biological contamination of foods include: the use of pesticides, fertilizers, and antibiotics around agricultural food products; accidental introduction of additives to industrially processed foods at unsafe levels, or intentional adulteration with low quality or unsafe ingredients for economic purposes; cross-contamination with allergens or other substances that can be dangerous to sensitive individuals (e.g., wheat gluten); microbial growth deriving from unsanitary agricultural or processing conditions; and spoilage during transport and storage of foods due to packaging defects or incorrect handling by consumers. To manage food safety risks, there is a continued need for rapid, sensitive, inexpensive, and reliable techniques to detect the presence of chemical contaminants and microbes in complex media.

Food Safety Solutions

Food testing and analyzing plays an important role in quality control of food production.

  1. Culture-based traditional techniques

Traditional culture methods use selective liquid or solid culture media to grow, isolate, and enumerate target microorganism and simultaneously prevent the growth of other microorganisms present in the food (Jasson et al., 2010). These methods for the identification of foodborne pathogens involve pre-enrichment growth, selective enrichment culture, and selective plating followed by biochemical identification and serological confirmation of results. These methods are relatively inexpensive, sensitive, and still regarded as gold standards, the main drawback of these methods is their long analysis time and labor intensiveness. The whole procedure takes typically between 7 and 10 days (Vunrcrzant and Pllustoesser, 1987; Biswas, 2005).

  2. Mircoscopic and optical characteristics based methods

Various methods based on microscopic and optical characteristics of the appropriately stained microbial cells have been developed for assuring microbial safety of foods and food products. These methods include Direct Epifluorescent Filter Technique (DEFT), Flow Cytometry, and Solid Phase Cytometry. DEFT is a rapid method for enumerating microbial foodborne pathogens and is used widely in the dairy industry for raw foods (Hermida et al., 2000), milk and milk products, beverages, foods, etc. Flow cytometry is applied for the enumeration of viable bacteria in a sample, and uses flourescent dyes for the analysis of viability, metabolic state, and antigenic markers of bacteria. Solid-phase cytometry (SPC) combines the principles of epifluorescence microscopy and flow cytometry.

  3. Immunological methods

All immunological methods for the detection of foodborne pathogens are based on antigen–antibody reactions. The body produces specific antibodies in response to invading pathogen. These reactions are versatile and specific but the success of an immunoassay depends on the specificity of antibody. Various kits have been developed based on immunological methods for the detection of foodborne pathogens, and are available commercially and have been responsible for revolutionizing the field of food testing (Table 1).

  4. Nucleic acid-based methods

Spurred by technological developments and commercial profit motives, nucleic acid-based assays have become widely available as powerful tools to assist in the diagnosis and monitoring of foodborne pathogens. These methods are based on the detection of specific gene sequences (signature sequences) in the genotype of target organism. The sequences may be selected in such a way that they can detect a particular group, genus, species, or even the strain of microorganism. There are many DNA-based assay formats, but probes and nucleic acid amplification techniques are the most popular ones and have been developed commercially for detecting foodborne pathogens.

  5. Mass spectrometry

For years, mass spectrometry has been considered the most suitable analytical technique for the detection of multiple compounds in food, feed and water. Coupled to liquid chromatography (LC), high-performance LC and ultra-high performance LC (HPLC, UHPLC) or gas chromatographic (GC) separation with an ionization source such as electrospray (ESI), a large number of mass spectrometry-based methods were developed to comply with updated regulations. To effectively apply this approach, the structure of the compound must be characterized before its detection. Methods development can be time-consuming, and standards must be acquired to optimize compound-specific instrumental conditions, including transition selections, ion-source voltages, and collision energies. MRM methods are, therefore, unable to screen for unknown compounds

Small molecule detection-Hapten based competitive immunoassay

Small molecules such as pesticides, drugs, etc. are usually nonimmunogenic and hence do not elicit an immune response unless coupled with some macromolecules such as proteins. It is, therefore, required to modify these small substances (hapten) for coupling with macromolecules (carrier) so as to make a stable carrierhapten complex. Synthesis of hapten for linking with carrier proteins is the most important aspect of specific antibody generation against small molecules for immunoassay applications.