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

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

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?

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?

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

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)).

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

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

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

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

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?

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

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

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

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

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

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

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?

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?

Next steps? Develop working group? Industry Consortium?

Thank You