Microbiological criteria and Microbiological testing

Question 1

Define microbiological criterion

Answer 1

A criterion defining the acceptability of a product, a batch of foodstuffs or a process, based on the absence, presence or number of microorganisms, and/or on the quantity of their toxins/metabolites, per unit(s) of mass, volume, area or batch.

Question 2

In contrast to FSOs and POs which only represent limits, a microbiological criterion consists of which 4 aspects?

Answer 2

1. The microorganisms of concern have to be stated
2. A qualitative or quantitative analytical method validated and chosen to give a sufficiently reliable estimate
3. Critical limits based on data appropriate to the food
4. A sampling plan including the sampling procedure and decision criteria for a lot

Question 3

Name the two different types of microbiological criteria in the EU

Answer 3

• Food safety criteria
• Process hygiene criteria

Question 4

What is food safety criteria?

Answer 4

• The acceptability of a product or batch of foodstuff applicable to products placed on the market
• Defined only for the pathogens/foodstuffs combinations for which testing samples placed on the market was considered an efficient contribution to public health

Question 5

What acts as a strong motivation to meet food safety criteria?

Answer 5

Risk of recalls, economic loss and loss of consumer confidence

Question 6

What is process hygiene criteria

Answer 6

• Criterion indicating the acceptable functioning of the production process.
• It sets an indicative contamination value above which corrective actions are required in order to maintain the hygiene of the process in compliance with food law

Question 7

Why is microbiological criteria needed?

Answer 7

• Useful for validation/verification of HACCP based processes and procedures
• Used to assess the acceptability of a batch of food (a harmonized approach).
• Used in EU legislation as a way to communicate the level of hazard control that should be achieved.
• Meeting criteria offers some assurance that particular pathogens are not present at unacceptably high concentrations, but does not guarantee “absence” of those pathogens.

Question 8

Microbiological criteria cannot be applied without …?

Answer 8

Microbiological testing

Question 9

What are the purposes of microbiological testing?

Answer 9

• Acceptance of a lot of raw materials, food ingredients or end products
• Establishment of shelf life of certain foods
• Monitoring of the production lines
• Monitoring of the hygienic status of the processing environment
• Verification of GHP and HACCP
• Baseline studies for the occurrence of specific microbes at a specific step(s) of production
• Surveillance at a specific step of production
• Outbreak investigations

Question 10

What are microbiological standards?

Answer 10

Used to determine the acceptability of a food with regard to a regulation or policy
Foods not meeting the standard are subject to removal form the market

Question 11

What are microbiological specifications

Answer 11

• Used by buyers of a food or ingredient to reduce the likelihood of purchasing a product that may be of unacceptable safety or quality
• Buyers throughout the food systems establish microbiological specifications for materials they purchase
• Specifications are advisory and the materials are sampled periodically

Question 12

What are microbiological guidelines?

Answer 12

• Established by either regulatory authorities, industrial trade associations or companies
• Indicate the expected microbial content of a food when best practices are applied
• Food companies use microbiological guidelines as a basis to design and assess their control systems
• Advisory in nature and may not necessarily lead to rejection of a food

Question 13

What must be done to bee microbiological criteria?

Answer 13

Food and food products must be tested
- Sampling a whole food lot would destroy it (neither is possible), so a representative sample is taken

Question 14

To meet microbiological criteria which features of a food/food product must be defined/assessed?

Answer 14

1. What type of hazard - can be either qualitative or quantitative
2. Food category E.g Ready-to-eat, minced meat intended to be eaten raw or cooked, cheeses, butter and cream made from raw milk, milk and whey powder, unpasteurised fruit and vegetable juices, some fishery products
3. Production or processing steps involved (Stage where the criterion applies)
4. Sampling plans (sample size, limits, analytical methods)
5. Interpretation of the test results and action in case of unsatisfactory results

Question 15

The sampling plan should define …?

Answer 15

“the probability of detecting microorganisms in a lot”

Question 16

What is the main limitation of a sampling plan?

Answer 16

No sampling plan can ensure the absence of a particular organism

Question 17

The two class sampling plan consists of the specifications n, m and c. What are the?

Answer 17

n = number of sample units from a lot to be examined
m = maximum acceptable number of relevant bacteria/gr
c = maximum acceptable number of sample units that may exceed the value of m; the lot is rejected if this number is exceeded
Example:
- Food safety criterion for Salmonella in minced meat: n=5, c=0, m=0/25g
- Five sample units analyzed from a lot, if one contains the pathogen the complete lot is unsatisfactory

Question 18

The three class sampling plan consists of the specifications: n, c, m and M. What are they?

Answer 18

c = number of sample units giving values between m and M
M is used to separate the acceptable from the unsatisfactory

Question 19

How is the three class sampling plan interpreted?

Answer 19

• Satisfactory if values are below m
• Acceptable if a maximum of c/n values are between m and M, the rest of the values observed are < m,
• Unsatisfactory if one or more of the values observed are >M or more than c/n values are between m and M.

Explain example:
- Process hygiene criterion for Enterobacteriaceae in egg products: n=5, c=2, m=10, M=100
- Five units from a lot tested, two can contain between 10-100 Enteros (giving only acceptable result)
- If three units are between 10-100, or one unit has greater than 100 Enteros, checks on the efficiency of the heat treatment and prevention of recontamination (unsatisfactory result)

Question 20

List the factors which affect the development of microbiological criteria

Answer 20

• The availability of a risk assessment.
• Dose-response data.
• Consumer exposure data.
• Data on microbial levels typically encountered in a food.

Question 21

The type of microbiological testing carried out depends on which factor?

Answer 21

Material to be tested:
- Excision (carcasses)
- Wet/dry swabbing (carcasses & surfaces/equipment)
- Whole carcass rinse (poultry)
- Meat sample (retail, 10g/25g)
- Batch sample (food products, raw ingredients: 25g or 25ml)

Question 22

In-house lab analysis for microbiological criteria is used when?

Answer 22

• Poultry uses widely, red meat and other foods/products less likely
• The laboratory conducting the microbiological testing must be either accredited, or must be supervised by an accredited laboratory

Question 23

What are the 6 stages of sample processing in a laboratory?

Answer 23

1. Sampling
2. Transport the samples to the laboratory
3. Remove the bacteria from the sample
4. Examine sample for target organism
5. Confirm suspect colonies
6. Calculate and report results

Question 24

What are the two methods for Bacteriological sampling of beef, pork, sheep, goats and horses carcasses in the slaughterhouses?

Answer 24

Destructive (excision with scalpel or borer)
Non destructive (wet/dry swabs, contact)

Question 25

Where are the 4 sites on the carcass for sampling for TAC and Enterobacteria in cattle?

Answer 25

• Rump
• Flank
• Brisket
• Neck

Question 26

Where are the 4 sites on the carcass for sampling for TAC and Enterobacteria in sheep?

Answer 26

• Flank
• Brisket
• Breast
• Lateral thorax

Question 27

Where are the 4 sites on the carcass for sampling for TAC and Enterobacteria in pigs?

Answer 27

Jowl
Back
Belly
Ham (back of hind leg)

Question 28

A swab sampling along the length of the carcass from caudal to cranial is used to test for which pathogen?

Answer 28

Salmonella

Question 29

When should sample be taken from a carcass?

Answer 29

After final inspection and before chilling

Question 30

Describe the key features of transporting a sample to the laboratory

Answer 30

• As quickly as possible
• Cool perishable samples to <4°C, maintain temp during transport to avoid changes in the level of microbiota
• Maintain frozen samples in a frozen state until analysis
• Canned foods should be maintained at <40°C

Question 31

List some problems associated with examination for pathogens

Answer 31

1. Fastidious organisms – may be difficult to culture
2. Usually in low numbers and/or low occurrence in food (“the needle in the haystack”) and/or non-uniformly distributed - so, we require large number of samples.
3. Hence, negative result does not necessarily mean the absence of the pathogen in the particular food:
   “The Absence of Evidence is not the Evidence of Absence”
4. Multistage methods of isolation, takes up to one week to confirm
5. Expensive!