1. Microbiological Sampling of Dairy Products
Erin Headley, M.S.
WAFP Meeting
June 13, 2018

2. What should we be testing? How should we be testing?
Agenda
Background
Risk Assessment
What to consider
Sampling Plans
What should we be testing?
How should we be testing?
Next steps & Discussion

3. Changing regulatory landscape
Background
Changing regulatory landscape
FSMA Supplier verification – how do we know if our suppliers are doing a good enough job testing?
Draft Listeria guidance document
Customers are requesting more information and/or updating their requirements too
[FDA] found Listeria in my cheese, why didn’t I?

4. What level is tolerable? Food Safety Objectives
Risk Assessment
What level is tolerable?
Food Safety Objectives
Maximum frequency/concentration of a microbial hazard in a food that is tolerable for consumer protection
Not more than 1µg/100g staphylococcal enterotoxin in cheese
The level of L. monocytogenes in RTE foods must not exceed 100 CFU/g at the time of consumption
The concentration of salmonellae in milk powder must be <1 CFU/kg
So how do I prove this?

5. Good sampling plans consider:
From ICMSF Book 7:
Severity/Likelihood of occurrence of the hazard
The susceptibility of the target consumers
The heterogeneity of distribution of microorganisms (how uniform is the distribution)
The randomness of sampling
The acceptable quality level (AQL – how many defective units are tolerable?)
The desired statistical probability of accepting or rejecting a nonconforming lot

6. What is your definition of a lot?
(Meriam Webster): All the members of a present group, kind, or quantity
ICMSF definition: a quantity of food or food units produced and handled under uniform conditions.
What is your definition of a lot?
All products within a batch
Single day of production
Clean-up to clean-up
For the purpose of the raw ground beef recordkeeping regulation, USDA has defined a lot as the amount of ground raw beef produced during particular dates and times, following clean up and until the next clean-up (9 CFR 320.1(b)(4)(iii)).

7. Types of Sampling Plans
Two-Class
Typically a presence/absence type of test
Positive or negative – most pathogen tests
Three-Class
The quality of the product can be divided into 3 classes (acceptable, marginally acceptable, unacceptable)
acceptable
unacceptable m M
marginallyacceptable
acceptable
unacceptable

8. What do all these letters mean?
n = number of sample units from the lot to be tested
c = maximum allowable number of sample units yielding unsatisfactory test results (presence of an organism)
m = a defined concentration separating acceptable quality from marginally acceptable quality
M = a defined concentration separating marginally acceptable quality from unacceptable quality

9. Combinations of Degrees of Health Concerns and Conditions of Use
“15” Cases from ICMSF Book 7

10. Combinations of Degrees of Health Concerns and Conditions of Use
Where would Listeria in cheese fall?

11. What should we be testing for cheese?
Pathogens?
Listeria
Salmonella
Staph?
Indicators?
Coliforms? EB?
Y&M?
Grade A vs. non-Grade A
Test the cheese or the environment, or a combination of both?

12. NACMCF - DOD appendix
Journal of Food Protection, Vol. 81, No. 1, 2018, Pages 115–141

13. NACMCF - DOD appendix
Journal of Food Protection, Vol. 81, No. 1, 2018, Pages 115–141

14. What are the right frequencies? Every vat? Every day?
When is it sampled?

15. The best sampling plans provide the opportunity for detection
How many samples?
The best sampling plans provide the opportunity for detection
More frequent sampling across multiple sites/time points gives a better chance of finding it

16. What about compositing or pooling?
Dry-Pooling
take 15 x 25g samples of NFDM from the lot = 375g
Run one Salmonella enrichment with that 375g
Composite = only test 1 x 25g out of that 375g
Enrich & follow method
15 x 25g samples
1 x 375g
sample
Katona, B. 2014

17. What about compositing or pooling?
Wet-Pooling
enrich separate individual samples, then add equal aliquots of the enrichment media to get the final test volume (ex: 5 x 1ml of each of 5 individual Listeria enrichments)
25g
25g
25g
25g
25g
Separate enrichments
Combine equal volumes of enrichments together & run analysis

18. Need to consider sample size
How are we going to test?
Validated methods
Government: BAM (FDA)
AOAC International (US)
AOAC Official Method Validations (OM)
AOAC-RI ‘Performance Tested Method’ Validations
AFNOR (France) – ex- Biomerieux Vitek kits
Others: ISO, NordVal, etc.
Need to consider sample size
Has the method been validated for that sample size and product matrix?

19. How do we better standardize this for dairy?
Next steps?
Develop the Food Safety Objective?
Define a lot for dairy/cheese products
What sample size do we use?
Should we composite or pool samples?
What methods can we use?
Who can help us validate them?

20. Next steps?
Develop working group?
Industry Consortium?

21. Thank You