Introduction to food detection I

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Introduction to food detection I

• Present by
• Srivalee T. ID4511782
• Patraporn S. ID 4518219

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Whats food safety ?

• Food safety
• A suitable product which when consumed orally
  either by a human or an animal does not cause
  health risk to consumer.

Why do we need all food to be safe?
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The answer is..........

• To protect consumers from the
  foodborne disease
• Foodborne disease
• Foodborne disease is any illness
  resulting from the consumption of food
  contaminated with one or more disease-producing
  agents. These include bacteria, parasites,
  viruses, fungi and their products as well as
  toxic substances not of microbial origin.

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The numbers and types of microorganisms
present on a food are affected by the following
factors

• the general environment which the food was
  originally obtain
• the microbial content of the food in the
  unprocessed state
• the sanitary conditions during the processing
• the adequacy of subsequence packaging, handling
  and storage conditions.

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Method of detecting foodborne disease

• Standard Plate count
• Direct microscopic count
• test for specific microbial pathogen
• Rapid detection technique

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Standard plate count

• Standard plate count is an agar plate method of
  estimeting viable bacteria population in terms of
  colony forming units (CFU).
• Viable number
• The number of specific cell in specific
  volume of material capable of dividing on or in a
  solid agar medium
• The viable number is expressed in terms of
  colony forming
• units (CFU)

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• The viable numbers or colony forming
  units (CFU) of bacteria suspension can be
  determined by use of the pour plate technique or
  the spread plate technique
• The spreading technique and pour plate
  technique can be used to determine the number of
  living (viable) organisms in various substances
  such as water, milk ,and foods during the various
  stages of bacteria growth curves.

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• The spread plate technique generally
  preferred for obligate aerobes while the pour
  plate are method is better for facultative
  anaerobes or microaerophilic cultures
• The process of using standard plate count is
  to dilute samples of the material to be tested
  with the agar medium, after 48 hours of
  incubation at 32 ?C visible colonies are count.
  

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Counting colonies on the plate can be done with a
Quebec Colony counter

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A modern colony counting system, the
system is design to count bacteria colonies.
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• After incubation, only those plate with 30
  to 300 colonies are used. Plate with higher
  counts are reported as too numerous to count
  .
• This 30 too 300 rule is statistically valid and
  the number of viable organisms in the original
  sample per milliliter is determined by
  multiplying the number of colonies per plate by
  the dilution factor of a particular plate .

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• How to calculate CFUs /ml?
• Example
• if 213 colonies were count in the 10-4 (1
  10,000) dilution plate. The number of organisms
  in the original sample would be calculate as
• Colony forming units (CFUs)
• mL of original sample
• Average no. of colonies x
  Dilution factor
• mL of original sample
• CFUs/ mL 213 x 10,000 ( or 213 x 10-4 )
• CFUs/ mL 2,130,000

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Demonstration of bacteria culture characteristics

• Microorganisms such as bacteria grow as
  visible accumulations of identical cells, forming
  colonies with different size,shape ,and overall
  general appearance of the bacteria colonies in
  the surfaces of agar media contain in Petridish

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culture media
The cultuvation of microorganisms
requires the use of nutrient preparations called
culture media contain soluble organic and
inorganic substances that are the necessary
factors for growth
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• Example
• Trypticase soy media is an excellent rich
  medium contain dipotassium phosphate, glucose ,
  phytone peptone, sodium dichloride and trypticase
  peptone and its suitable for all Bacteria
  culture.

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• Selective medium
• Selective medium is defined as one that permits
  the growth of certain organisms while preventing
  or retarding the growth of others. The selection
  can be carried out to
• control of ingredients of the medium.
• alteration of atmospheric components.
• adjustment of incubation temperature.
• Differential medium
• Differential media will cause different
  colonies to develop differently from other
  organisms present.

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Other factors that influence microbial growth

• Temperature
• Oxygen
• pH
• Osmotic pressure

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Temperature
Psychophiles Mesophiles
Psychotroph Thermophiles Extreme Thermophiles
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Temperature
Psychophiles 5-20 ?C Mesophiles 20-50? C
Psychotroph Thermophiles 50-80?C Extreme
Thermophiles ? 80 ? C
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Oxygen
Obligate aerobes Obligate anaerobes Facultative
anaerobes Microaerophilic Aerotolerant
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Oxygen
Obligate aerobes bacteria species that can grow
on the presence of Oxygen Obligate
anaerobes Bacteria that cant grow on the
presence of Oxygen because its toxic to
them Facultative anaerobes Bacteria species that
can grow well under both aerobic and anaerobic
condition Microaerophilic Bacteria that can grow
poorly in the presence of Oxygen Aerotolerant Bact
eria that can grow on the presence of Oxygen but
do not use it
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pH
Acidophile Neutraphile

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pH
Acidophile prefer pH range around
4-6 Neutraphile prefer pH range 6.5-7.5

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Osmotic pressure
Hypotonic The environment that exhibit lower
solute concentrations that are found within the
cell Hypertonic The solute concentration is
lower inside then the outside of the
cell Isotonic The solution that contain solute
concentration close to that of cytoplasm
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Osmotic pressure
Hypotonic The environment that exhibit lower
solute concentrations that are found within the
cell Hypertonic The solute concentration is
lower inside then the outside of the
cell Isotonic The solution that contain solute
concentration close to that of cytoplasm
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Rapid detection techniques

• Rapid methods generally means any method which
  yields results quicker than the standard method.
• Enzyme Linked Immunosorbent Assays
• (ELISA)
• Impedance (or conductance),
• Immunomagnetic separation (IMS)
• bioluminescence.

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Enzyme Linked Immunosorbent Assays (ELISA)

• ELISA is most commonly capture the target
  antigen
• The captured antigen is then detected using a
  second antibody which may be conjugated to an
  enzyme.
• A wide range of enzyme-linked immunosorbent
  assays (ELISA) are commercially available,
  especially for Salmonella, pathogenic E. coli and
  Listeria.

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Enzyme Linked Immunosorbent Assays (ELISA)

• The technique generally requires the target
  organism to be 106 cfu/ml, although a few tests
  report a sensitivity limit of 104
• Immunoassays may be performed either as the
  'standard' ELISA tray

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The end.