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It is estimated that 1 in every 6 individuals living in the United States will get sick as a result of exposure to foodborne pathogens each year. Of these 48 million people, 128,000 will be hospitalized and 3,000 will die. Recent advancements in sensor technology have greatly improved the ability of food manufacturers to adequately detect the presence of these pathogens before their shipment to consumers.
Purpose of Food Safety
Throughout the entire food manufacturing processes, there are many different ways in which unwanted microorganisms can enter food products and ultimately cause a variety of unwanted health effects to the consumer. Microbial contamination by bacteria can also cause food products to quickly spoil, ccosting both consumers and food manufacturers a considerable amount of money over time.
In an effort to prevent the unwanted contamination of food products by microorganisms, various food safety measures are taken prior to shipment of these items. For example, both Hazard Analysis Critical Control Points (HACCP) and Failure Modes and Effects Analysis (FMEA) are two widely used risk assessment tools that determine whether any food samples that have been taken at various points in the manufacturing process are at risk of contamination.
Current Food Safety Technology
Both destructive and nondestructive analytical techniques are currently used to assess food products. These analytical techniques, of which can include chromatography, spectrometry, electrophoresis and titration, are often accompanied by specific detectors such as flame ionization (FID) and thermal conductivity (TCD) for gas chromatography.
Unfortunately, these techniques often require a considerable amount of time for both sample preparation and the analysis procedure to be completed before any definitive data is produced. Furthermore, many of the non-destructive techniques that are useful for food safety monitoring are insufficient for large-scale commercial purposes.
Optical Sensors and Food Safety
As compared to conventional analytical methods, optical biosensors are superior in their ability to accurately detect the presence of analytes within complex matrices. For food safety purposes, biosensors show particular promise in their capacity to obtain precise measurements on the concentration of pathogens, pesticides, drug residues, heavy metals and other potentially toxic substances in a wide variety of sample types.
There are various different optical geometries that have been used for biosensors within the food industry. These include optical fibers, planar waves, surface plasmon resonance and microarrays. Regardless of which geometry is chosen, all optical biosensors must be capable of measuring a change in the amplitude, phase, frequency or polarization of light.
Fiber Optic Biosensors
The detection of optical signals by fiber optic cables is often noted for its reduced interference, loss of signal and noise as compared to other optical geometries. The main components of optical fiber biosensors that are responsible for these advantages includes its light source, optical transmission medium, immobilized biological recognition element, optical probes and optical detection system. As the light beam travels through a fiber-optic cable to the sample, it is then reflected and transferred through a second fiber-optic cable that allows this signal to be sent to the detector for measurement.
Fiber optic biosensors can be classified as either intrinsic sensors, in which the sample of interest is directly interacting with a component of the optical fiber, or extrinsic sensors, in which the optical fiber directs the movement of the light beam from the light source through the sample. Both intrinsic and extrinsic optical fiber biosensors can be further enhanced with the addition of specialized detectors that are based on a variety of technologies such as:
- Fluorescence spectroscopy
- Photo multiplier tube (PMT)
- Charge coupled device (CCD)
- Avalanche photo diode (APD)
Surface Plasmon Resonance-Based Fiber Optic Plasmonic Sensors
The biological applications of fiber optic plasmonic sensors (FOPSs) for biological purposes are numerous, ranging from medical diagnostic devices to lab on a chip. More recently, the incorporation of surface plasmon resonance (SPR) technology into FOPSs has improved the sensitivity of these sensors while also enabling label-free sensing and a more rapid response during their use.
The usefulness of SPR for this purpose is dependent upon the availability of a specific ligand that can be immobilized onto the SPR chip. When these components are available, the SPR technique is particularly useful for concentration analysis. Furthermore, the portability of SPR technology that has been incorporated into biosensors is also advantageous to ensure rapid food monitoring. Recent applications of SPR-based sensors for food safety have been applied for the on-site analysis of antibiotics present in milk samples.
For food safety and quality assurance purposes, SPR-based FOPSs have been developed from the same sensors that have been successful in drug discovery applications. For example, a novel blood glucose fiber optic grating sensor that exhibits an extremely tilted index fringe structure has been shown to detect glucose concentrations within the physiological range of 0 to 3.0 mg/ml. This sensor exhibits a particularly high refractive index sensitivity and Q-factor, as well as a better linearity as compared to similar biosensors. As a result of these findings, researchers are hopeful that the same techniques used to develop this glucose biosensor can be applied for the development of other label-free microstructural sensors for food safety analysis.
References and Further Reading
- “Estimates of Foodborne Illness in the United States – Findings” – Centers for Disease Control and Prevention.
- Adley, C. C. (2014). Past, Present and Future of Sensors in Food Production. Foods 3; 491-510. DOI: 10/3390/foods3030491.
- Terry, L. A., White, S. F., & Tigwell, L. J. (2005). The Application of Biosensors to Fresh Produce and the Wider Food Industry. Journal of Agricultural and Food Chemistry. DOI: 10.1021/jf040319t.
- Narsaiah, K., Jha, S. N., Bhardwaj, R., Sharma, R., & Kumar, R. (2012). Optical biosensors for food quality and safety assurance – a review. Food Science Technology 49(4); 383-406. DOI: 101007/s13197-011-0437-6.
- Khansili, N., Rattu, G., Krishna, P. M. (2018). Label-free optical biosensors for food and biological sensor applications. Sensors and Actuators B: Chemical 265; 35-49. DOI: 10.1016/j.snb.2018.03.004.