Regulations and control: Microbiological criteria

What is microbiological criteria?

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

Outline the Food Safety Objective concept

What is the key difference between FSOs and POs cf to MC

• FSOs and POs represent limits

• MC consists of several aspects

List the aspects that MC includes

• The microorganisms of concern have to be stated,

• Qualitative or quantitative analytical method validated and chosen to give a sufficiently reliable estimate

• Critical limits based on data appropriate to the food, and

• Sampling plan including the sampling procedure and decision criteria for a lot

What are the two different types of microbiological criteria in the EU?

• Food safety criteria- acceptability of a product placed on the market

  • Response= whole batch will be destroyed

• Process hygiene criteria- acceptability of function of production process

  • Response = HACCP plan will be increased

What is the purpose of microbiological criteria?

• Validation and verification of HACCP based procedures

• Assess acceptability of a batch of food

• Communicate level of hazard control

• Some assurance that particular pathogens are not present at unacceptably high concentrations (never guarantee of abscence)

What is needed in order for microbiological criteria to be applied?

Microbiological testing

What can microbiological testing be used for?

• 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

What is the difference between mandatory and advisory microbiological criteria?

Microbiological standards = mandatory criteria

• determine the acceptability of a food

• not meeting the standard are subject to removal

• Established by regulatory authorities

Microbiological specifications = advisory

• Buyers of a food or ingredient establish specifications (e.g.- if they need certain things for what they are making)

Microbiological guidelines = advisory

• indicate the expected microbial content of a food when best practices are applied

• companies use as basis to design + assess control systems

• established by either regulatory authorities, industrial trade associations or companies

What must be defined in a microbiological criterion?

• Type of hazard (qualitative or quantitative)

  • Pathogen or

  • Indicator/ Index organisms (either quant or qual) e.g.- ACC, E. coli

• Food category

• Production or processing steps involved (Stage where the criterion applies)

• Sampling plans (sample size, limits, analytical methods)

  • Two class sampling plan (Used almost exclusively for pathogens)

  • three class sampling plan (applied for indicator organisms)

• Limits

• Interpretation of the test results and action in case of unsatisfactory results

What are the specification used in two class sampling plan?

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

What are the two types of interpretation in a two class sampling plan?

• satisfactory, if counts or values <m

• unsatisfactory, if counts or values >m

Explain the additional specification in the three class sampling plan?

M is used to separate the acceptable from the unsatisfactory

c = number of sample units giving values between m and M

1. Satisfactory: <m

2. Acceptable: if a maximum of c/n values are between m and M, and the rest of the values observed are < m- (for example only one or two samples are >m but less than M don't get rid of entire batch)

3. Unsatisfactory: if one or more of the values observed are >M or more than c/n values are between m and M.

What are the different ways that microbiological sampling can be performed?

Can be destructive (excision with scalpel or borer) or non destructive (wet/dry swabs, contact):

• 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)

Then the lab test can either be in house (common in poultry) or external/commercial lab

What are the stages in the sample processing?

• Sampling

• Transport the samples to the laboratory

• Remove the bacteria from the sample (homogenisation)

• Examine sample for target organism

• Confirm suspect colonies

• Calculate and report results

List the sample sites for TAC and enterobacteriae in cattle, sheep and pigs (swabbing or excision)

Areas more likely to be contaminated by environment

4 sample sites of each carcass

What is the sampling area for salmonella, in cattle, sheep and pigs when swabbing?

Limit is presence or abscence, so want to increase chance of pickign up bacteria

an abrasive sponge sampling method shall be used

Under what conditions should samples be transported to the lab?

• Cool perishable samples to <4°C and 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

• Max time from sampling to exam often given in ISO methods

What are the problems associated with exam for pathogens?

• Fastidious organisms

• Low numbers and/or occurrence so require large no of samples

  • Negative result not necessarily abscence

  • non-uniformly distributed

• Multistage methods takes up to a week to confirm

• Expensive

What are the steps of pathogen samplig and ID?

• pre-enrichment

• enrichment

• presumptive ID

• ID

What must happen before any result can be reported and how is this done'

Confirmation

• Gram staining

• Biochemical tests —> Catalase, oxidase, urease, methyl red, Vogues-Proskauer, carbohydrate fermentation

• Commercial biochemistry kits – API

• Latex agglutination - E. coli O157, S. aureus

• Serology testing - Salmonella spp.

Which factors may affect the results of a microbiological test?

• All stages in sample processing:

  • Transport, homogenization, media, counting/calculation of bacterial numbers

• Microorganism not detectable or damaged (“Viable but not countable” forms)

• Human error throughout

What is the excision criteria for cattle, sheep, goat, horse and pig carcasses?

dont need to know numbers