class lecture 4

7/30/2019 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

class lecture 4

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