class lecture 4
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Food Microbiology
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Indicator Organisms
REFLECTS microbiological quality
organisms and/or their metabolic
products whose presence in given foods at
certain levels may be used to assess existing
quality or better, to predict product shelf
life
Jay
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Need for Microbiological Criteria
Evidence of Hazard
Natural microflora
Processing
Contamination
Consumer
State of Distribution
Abuse
Spoilage Potential
Ultimate Consumption
Reliability of
Detection
Costs and Benefits
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Definitions
Standards
Listeria monocytogenes
E. coli O157:H7
Guideline
Salmonella testing
GenericE. coli Testing
Specifications
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Types of Microbial Indicators
Aerobic Plate Counts
Coliforms
E. coli
Enterococcus
Yeast and Mold Counts
Can Indicate Quality and/or Safety
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Indicators of Quality
Shelf-life often determined by initial
number of organisms present
NOT a direct correlation
Must consider
Food Type
Processes
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Criteria - Indication of Quality
Present and Detectable
Correlation to product quality
Detected and distinguishableEnumerable in short period
Not affected by food flora
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Criteria - Indication of Quality
Present and Detectable
Correlation to product quality
Detected and distinguishableEnumerable in short period
Not affected by food flora
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APC as an Indicator
Only measure Live Cells
Little Value in Organoleptic Value
Quality Loss May Occur at Low Counts
MUST know expected values at particular
point in process of particular food
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APC as an Indicator
Compliance with Standards or Guidelines
Purchase Specifications
Monitor Adherence to GMS or SSOPs
Monitors various organisms Thermodurics
Mesophiles
Psychrotrophs
Thermophiles Proteolytic
lipolytic
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Criteria -Indicators of Food
SafetyEasily and Rapidly Detectable
Distinguishable
Association to PathogenPresent when Pathogen Present
Numbers, Growth and Death Correlate to
PathogenAbsent from Foods that are Free of the
Pathogen
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Ideal Relationship Between a Pathogen
and an Indicator Organism
Time
Numbers
Indicator
Pathogen
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Safety Indicators
Reduce or Eliminate Food-borne hazard
Applied to Food Products frequently
associated with contamination
Considerations
Type of Food
Numbers
Consumer
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Coliforms
GRAM NEGATIVE, NONSPORE-
FORMING RODS THAT FERMENT
LACTOSE TO ACID AND GAS WITHIN
48 HOURS AT 37 C
KNOW THIS!!!!!!!!!!!
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Coliforms
FamilyEnterobacteriaceae
Genera
Citrobacter
Enterobacter
Escherichia
Klebsiella
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Coliforms
Growth
Temperature
pH
Nutrients
Survival
Distribution
E. coli
Enterobacter
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Finding Coliforms
Fecal contamination
Lack of Sanitation
Increased Likilihood of Pathogen Presence
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Limitations of Coliforms as
Indicators
Raw Foods
Heat Processed vs Raw Consumption
Heat Processed
Human
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Coiform Criteria and Standards
Examples
NMT 10/ml for Grade A Pasteurized Milk and
milk products
NMT 10/ml for precooked and partially cooked
frozen foods
NMT 100/ml for crabmeat
NMT than 100/ml for custard-filled items
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Indicators of Safety - Fecal
Specificity
High Numbers in Feces
High ResistanceEasy and reliable Detection
Non-pathogenic
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Fecal Coliforms and E. coli
Easily destroyed by heat
May die during Freezing and Storage
E. coli indicates FECAL contamination andpossibly the presence of enteric pathogens
Failure to detect does not mean pathogen
free
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Fecal Coliforms
Production of acid and gas in EC (E. coli)
broth between 44 and 46 C
Fecal Coliforms are E. coli Biotype I
EHEC
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Enterococci
Fecal Material
Plants
Salt-TolerantResistant to Freezing
Few reasons to specify presence of
Enterococci within coliform group
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Recommendations
Table 20-3
Acceptable and unacceptable ranges of
coliform and E. coli counts
NOT necessarily a regulation, just a
guideline
HELPFUL in special projects
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Special Considerations
Vegetables
Enterobacter a natural inhabitant
Must look at E. coli
Meats Aeromonas and psychrotrophic enterics are coliforms
Must look at E. coli
Cooked Products
No Coliforms should be present
Pasteurized milk
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