METHOD FOR THE MICROBIOLOGICAL EXAMINATION OF FOODS

1205 324 FOOD INDUSTRIAL MICROBIOLOGY

METHOD
PLATE COUNT DEPENDS ON
DILUENT
FOOD HOMOGENATE
DILUTION SERIES
MEDIUM
PLATING METHOD
INCUBATE CONDITIONS
BAIRD-PARKER AGAR
SELECTIVE AGENT
Sodium tellulite
Lithium chloride
ELECTIVE AGENT
Sodium pyruvate
Glycine
DIAGNOSTIC AGENT
Egg yolk
DISADVANTAGE OF PLATE COUNT ???
APPLICATION OF PLATE COUNT
CHECK QUALITY OF RM & FINAL PRODUCTS
CHECK CONDITION HYGIENE
ESTIMATE STORAGE LIFE OF PRODUCTS
DETERMINE
Production
Transport
Storage
DETERMINE PATHOGENS
SELECTION OF MEDIA IN FOOD MICROBIOLOGY
STREAK TECHNIQUE
MOST PROBABLE NUMBER
MOST PROBABLE NUMBER (MPN)
MULTIPLE TUBE TECHNIQUES
MOST PROBABLE NUMBER
MICROSCOPIC COUNT
MICROSCOPIC COUNT
COMPARISON OF SENSITIVITY OF METHOD
DYE-REDUCTION TEST
INDICATORS
ATP PHOTOMETRY
ATP : ADENOSINE TRIPHOSPHATE
Synthesis of new cell
Active transport (uptake of materials from environment)
Movement
Light production
ATP PHOTOMETRY
LUCIFERIN + LUCIFERASE + ATP + O2
OXYLUCIFERIN + LUCIFERASE + AMP + LIGHT
ATP PHOTOMETRY
BACTERIA CELL
1 fg of ATP
YEAST CELL
100 fg of ATP
ATP PHOTOMETRY
BREAK DOWN THE NON-MICROBIAL CELLS IN FOOD
REMOVE NON-MICROBIAL ATP USING ATPASE
RELEASE ATP FROM BACTERIA CELL
ADDITION OF LUCIFERIN & LUCIFERASEE
RECORD LIGHT EMISSION (ATP PHOTOMETRY)
ATP PHOTOMETRY
APPLICATION
FRESH MEAT
MILK
STARTER CULTURE
TEST UHT MILK
SURFACE CONTAMINATION
ATP PHOTOMETRY
DISADVANTAGE
MIXED BACTERIA & YEAST CELL
DILUTION
REMOVE CELL BEFORE ATP MEASURED
Filtration
Centrifugation
DIRECT EPIFLUORESCENT FILTER TECHNIQUE (DEFT)
LIQUID FOOD
FILTER THROUGH MEMBRANE
ACRIDINE ORANGE : FLUORESCENT DYE (FLUOROCHROME) POUR THROUGH FILTER
EPIFLUORESCENT MICROSCOPY
COUNT: MANUAL OR AUTOMATIC
DIRECT EPIFLUORESCENT FILTER TECHNIQUE (DEFT)
ACRIDINE ORANGE BINEDS TO:
RNA — fluorescent orange
DNA — fluorescent green
VIABLE CELL
RNA > DNA — orange
NON-VIABLE CELL
DNA > RNA —green
DIRECT EPIFLUORESCENT FILTER TECHNIQUE (DEFT)
ELECTRICAL IMPEDANCE METHOD
IMPEDANCE : RESISTANCE
BACTERIA GROWTH
—-decrease impedance
—-increase conductivity
ELECTRICAL IMPEDANCE METHOD
BACTOMETER
VARY TEMP
SMALL VOLUME
MANY WELLS
Many samples
AUTOMATIC
ELISA
ANTIGEN – CONJUGATE ENZYME
ANTIBODY – CONJUGATE ENZYME
ENZYME-LINKED IMMUNOSORBENT ASSAY
ANTIBODY
ANTIGEN(TOXIN)
ENZYME
Alkaline phosphatase (ALP)
Horse Radish Peroxidase (HRP)
SUBSTRATE
Tetramethylbenzidine (TMB) + 30% H2O2
Azinobis sulphonic acid (ABTS)
o-phenylinediamine (OPD)
p-nitrophenyl phosphate
SANDWICH-ELISA
ENZYME-LINKED IMMUNOSORBENT ASSAY
ANTIBODY
ANTIGEN(TOXIN)
ENZYME
Alkaline phosphatase (ALP)
Horse Radish Peroxidase (HRP)
SUBSTRATE
Tetramethylbenzidine (TMB) + 30% H2O2
Azinobis sulphonic acid (ABTS)
o-phenylinediamine (OPD)
p-nitrophenyl phosphate
ELISA
QUALITATIVE RESULT COLOR
QUANTITATIVE RESULT
Micro ELISA reader
Spectrophotometer
Standard curve
THE END

…