FOOD TESTING AND RAPID DETECTION OF FOOD

·         Country’s food regulator, Food safety standards authority of India (FSSAI) has made a quick progress towards the use of advanced technologies for food Testing in the year 2019.

    ·         Several new rapid food tasting kits/devices for detection of food borne pathogens and toxins have been introduced during the year 2019.

       ·         This ensures “faster, better, cheaper” real time testing of food.

    ·         FSSAI provides these kits to the state government for use by field officers and get quicker and validated results for various foods such as milk and edible oil among other.

       ·         Initiation- eProcurement market place portal ( GeM).

       ·         FSSAI has so far introduced 30 rapid food Testing kit / devices under these regulations.

Conventional methods 

·         Conventional bacterial testing methods rely on specific media to enumerate and isolate viable bacterial cells in food.

·        These methods are very sensitive, inexpensive and can give both qualitative and quantitative information on the number and the nature of microorganisms present in the food sample.

   ·         Traditional methods for the detection of bacteria involve the following basic steps:

ü  Pre-enrichment.

ü  Selective enrichment.

ü  Selective plating.

ü  Biochemical screening.

ü  Serological confirmation.

·         Hence, a complete series of tests is often required before any identification can be confirmed.

·         These conventional methods require several days to give results because they rely on the ability of the organisms to multiply to visible colonies.

·         Moreover, culture medium preparation, inoculation of plates and colony counting makes these methods labour intensive. Conventional methods generally regarded as the golden standard often takes days to complete the identification of viable pathogens.

Rapid detection of Food

·         Any modification that reduces the analysis time can technically be called rapid method.

Need For Rapid Methods

To reduce human errors·

Validation·

Automation and computerization·

Simplicity·

To save time·

To save labour cost·

·                                         The effective testing of bacteria requires methods of analysis that can meet a                     number of challenging criterion.

·                                         The food industry is in need of more rapid methods which are sensitive.

Rapid methods can be classified into the following categories 

•               Modified and automated conventional methods

•               Biosensor's

•                Bioluminescence biosensor

•                Impedimetry (electrical impedance)

•                Piezoelectric biosensors

•                Flow Cytometry

•                Solid phase Cytometry

•                Electronic nose

•               Immunological methods

•               Nucleic acid based assays

•                DNA hybridization

•                Polymerase chain reaction (PCR)

Modified and automated conventional methods

·         Conventional methods used traditionally for microbial analysis are regarded as gold standards except for time delay and labour involved.

·         Many attempts have been made to improve laboratory efficiency by making the procedures for traditional agar based methods more convenient, user friendly and to reduce the cost of material and labour.

·         Several modifications in sample preparation, plating techniques, counting and identification systems have made these conventional methods faster and easier.

ü  Sample preparation.

ü  Stomacher.

ü  Pulsifier.

ü  Plating technique.

ü  Dip slides.

ü  Use of flurogenic and chromogenic substrate.

ü  Petri films.

ü  Hydrophobic Grid Membrane Filter (HGMF).

ü  Colony counting.

ü  Identification systems.

Biosensors

·         Biosensors are defined as indicators of biological compound that can be as simple as temperature sensitive paints or as complex as DNA-RNA probes.

  ·         The science of biosensor is a multidisciplinary area.

·         Many of the system are portable and hence can be used for field testing or on the spot analysis and are rapid test which are capable of testing multiple analysis simultaneously.

·         Bio sensing methods for pathogen detection are centred on four basic physiological or genetic properties of microorganisms:

ü  Metabolic patterns of substrate utilization,

ü  Phenotypic expression analysis of signature molecules by antibodies,

   ü  Nucleic acid analysis and the analysis of the interaction of pathogens with eukaryotic cells.

 

Bio luminescence sensors

Utilization of the ability of certain enzymes to emit photons as a byproduct of their reaction. used to detect the presence and biological condition of the cells.

·         ATP bioluminescence

·         Bacterial bioluminesce

·         Fiber optic biosensor 

Electrical impedance biosensor

·         Impedance microbiology detects microbes either directly due to production of ions from metabolic end products or indirectly from liberation of CO2.

·         This method is well suited for detection of bacteria in clinical samples and to monitor quality and detect specific food pathogens. 

Piezoelectric biosensors

·         This system is very attractive and offers a real time output, simplicity of use and cost effectiveness.

·         The general principle is based on coating the surface of piezoelectric sensor with a selective binding substance for example antibodies to bacteria and then placing it in a solution containing bacteria.

Flow cytometry

·         This may be considered as the form of automated fluorescence microscopy in which instead of sample being fixed to a slide, it is injected into a fluid (dye), which passes through a sensing medium of flow cell.

·         This system is highly effective means for rapid analysis of individual cells at the rate of thousand cells per second.

 

Solid Phase Cytometry (SPC)

·         SPC is a novel technique that allows rapid detection of bacteria at single cell level, without the need for growth phase

 

Electronic nose

·         This system comprises of sophisticated hardware with sensors, electronics, pumps, flow controllers, software's, data pre-processing and statistical analyzer.I

·         In microbiology the smell of the cultural bacteria often provides a clue to the identification of the organisms present which requires skill.

Immunological methods

·         Immunological methods rely on the specific binding of an antibody to an antigen.

·         Immunoassay refers to the qualitative and quantitative determination of antigen and antibody in a specimen by immunological reaction.

 

Nucleic acid based assays

·         Advances in biotechnology have led to the development of a diverse array of assay for detection of food pathogens.

·         Rapid analysis that used nucleic acid hybridization and nucleic acid amplification techniques offer more sensitivity and specificity than culture based methods as well as dramatic reduction in the time to get results.

DNA Hybridization

·         The identification of bacteria by DNA probe hybridization is based on the presence or absence of particular genes.

Polymerase Chain Reaction

·         The PCR is an in-vitro method used to increase number of specific DNA sequence in a sample.

·         PCR is used increasingly in research in food microbiology because of its high sensibility or specificity.