Biosensors in food analysis

Contents

1. Introduction of biosensors
2. Technology (brief)
3. Electrochemical Biosensors
4. Piezoelectric biosensor
5. Thermometric biosensors
6. Optical biosensors
7. Food analysis and application of biosensors

Introduction of biosensors

Biosensors can be defined as an analytical device containing biological or biologically derived sensing elements. They can also be described as the offspring of biology and electronics. Multidisciplinary skills of biologists, physicists, chemists and engineers have been combined to produce biosensors. In a biosensor the analyte or the sensing element could be a bio catalyst such as an enzyme, organism, tissue or an affinity system such as an antibody, or a nucleic acid.

Technology

As a result of the development of the microprocessor applied technology and rapid growth of biotechnology, production and application of biosensors expanded dramatically. Quality assessment and ensuring compliance with legislation are the two basic needs of food analysis. Although human sense organs are sensitive, instruments provide better quantitative results than them. However conventional instrumental methods are incompatible in cases where quick results are needed. In addition to this, biosensors have various advantages as compared to conventional analytical methods. They are relatively cheap, easy to handle, portable and the user does not require special skills. The term biosensor is used for a whole class of sensors that utilize a biochemical reaction to determine a specific compound.

In a biosensor a bio-receptor molecule is immobilized in a suitable matrix to form a bio-layer which is then placed in the immediate vicinity of a transducer. Depending on the nature of the transducers and the transduced parameter, there are different types such as Electrochemical, Piezoelectric, and Thermometric and Optical biosensors in the analytical field.

Electrochemical Biosensors

An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element.

Piezoelectric biosensor

The development of a piezoelectric biosensor based on nucleic acids interaction is presented focusing on the methodology for probe immobilization. This is a key step in any DNA biosensor development. Often, the detection limits and, in general, the analytical performances of the biosensor can be improved by optimizing the immobilization of the receptor on the transducer surface.

Thermometric biosensors

Thermometric biosensors are constructed by combining enzymes with temperature sensors. When the analyte is exposed to the enzyme, the heat of reaction of the enzyme is measured and is calibrated against the analyte concentration.

Optical biosensors

Optical Biosensors provides the most comprehensive analysis of optical biosensors and relevant technologies to date. According to the optical configuration, optical sensors have classified into two modes. When light is reflected at an optical interface where there is a change of refractive index, there is a decay of energy from the point of reflection into the surrounding medium. This energy field which extends into the medium depends upon the medium in which the wave guide is dipped. The resultant changes of luminescence, absorption or fluorescence can hence be determined. When the glass surface of the biosensor is coated with a thin layer of metal (silver, gold), the intensity of the resonance angle changes depending on the concentration of the medium in which electrode is immersed. This phenomenon is called the surface plasma resonance (SPR).

Food analysis and application of biosensors

Dietary habits of people throughout the world are different depending on the availability, ethnicity, cultural influences and the preparation and preferences for food. The range of food analytes comprises of liquid and gases as ionic radical or neutral species. The form of analyte may range from macromolecule to a microelement and heterogeneous distribution of analyte in the food has made the situation worse for the analyst. In most cases, the analyst needs to separate the analyte from the food before detection.

In food industry optic coated with antibodies are commonly used to detect pathogens and food toxins. The light system in these biosensors has been fluorescence, since this type of optical measurement can greatly amplify the signal. The exact wave length of this resonance depends on the amount of antibody, immobilized in the coupling matrix. The antibody-antigen interaction causes a shift in the resonance to longer wavelengths. The amount of the shift can be related to the concentration of antigens. The speed of detection is critical in preventing and diagnosing food related illnesses. It plays an important role in food processing plants by minimizing time gap between two unit operations. In conclusion, biosensors form an interesting part of food analysis, and they have achieved a notable success. However the have not yet reached their full potential and new products are being manufactured every movement.

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