Validation Challenges for Makers of Unpasteurized

American Cheese Society Conference - July 28,2018 –Pittsburgh Pa. Robert Wills Cedar Grove Cheese and Clock Shadow Creamery Food Safety Plan

Process Flow Diagram Hazard Analysis – Microbiological Risk Assessment Preventive Controls Preventive Controls Analysis

Supplier Controls and Process Controls Critical Control Points Comparable Hurdles Validation Verification What is Validation?

Scientific Evidence that Controls Will Result in Safe Cheese Maybe Literature Maybe Results of Studies Maybe Regulatory Standards Pasteurization as an Example

 Validated Scientific Evidence that Pathogens will be reduced by a factor of more than 100,000 cfu/g. (referred to as a 5 log reduction).  Accepted as a Regulatory standard  Legal Pasteurization requirements include evidence that mandatory minimum time and temperature was achieved, viz. 1610 F. for 15 seconds or 1450 F. for 30 minutes.  Tamper proof (sealed) and designed to assure every drop of milk treated  Records of measurement to provide Verification Non-pasteurized Cheese expected to Meet Comparable Standards

 Five log reductions may accumulate over the production process.  Possibly can achieve by showing exclude introduction of pathogens  Must be able to show for each piece of cheese  Must establish procedures that cannot be by- passed  Must create records that verify procedures were followed  We want comparable comfort level Session Goals

Focus on a Research Agenda for Safe Food Production, Not Regulatory Requirements Develop a Blueprint for Gathering Evidence of Validity Identify Applicable Conditions and Cheese Characteristics for a Safety Process Select the Most Promising and Widely Applicable Examples out of a Vast Number of Potential Interventions? Identify Opportunities to Share Research Costs and Results Simplified Flow Exclude Pathogens from Plant

Zone Isolation Supply Controls on Ingredients Supply Control on Milk Treating Milk and Other Ingredients

Pasteurization Heat Treatment Ultraviolet Light Ozone Pressure Sonic Peroxide Culture Addition

Competitive Cultures – Use Up Food Supply Protective Cultures – Release Enzymes or Toxins that Control Pathogens Targeted Bacteriophage Process Steps

Heat Treatment of Milk to Precipitate Curd, e.g. Ricotta High Levels of Acidity in Cheese Cooking Cheese, e.g. Juustoleipa Product Formulation

Low Moisture Low pH High Salt Aging

Holding Time and Temperature 60 day rule Surface Conditions and Treatments Focus Areas for Discussion How Can We Establish Science?

Challenge Studies on Whole Process

Challenge Studies on Part of the Process

Literature Review – Body of Knowledge Food Safety Plan

Process Flow Diagram Hazard Analysis – Microbiological Risk Assessment Preventive Controls

Validating the Safety of Cheese Made with Unpasteurized Milk

Kathleen A. Glass, Ph.D. Distinguished Scientist, Associate Director Food Research Institute University of Wisconsin-Madison [email protected]

CLOSING THE VALIDATION GAP FOR RAW MILK PRODUCERS UNDER PREVENTIVE CONTROLS FOR HUMAN FOODS Society Annual Conference, Pittsburg, PA, July 28, 2018 Developing Safe Cheese Made with Unpasteurized Milk

• What are the risks? • How can risks be controlled? • How are preventive controls validated? • What research is still needed? • Summary

20 What are the risks: Presence of Pathogens in Raw Milk and Cheese • Low levels of pathogens are present in raw ingredients and environment • JFP 2008: Prevalence in milk in 11 Vermont farms . ~35% Staphylococcus aureus; 2.3% Listeria, 0.75% virulent E. coli • FDA 2016: ~1% raw milk positive for one or more pathogens . Salmonella, Listeria monocytogenes, E. coli O157:H7 . Indicator organisms did not correlate well with pathogens 21 21 Are there illnesses associated with 60-day aged raw milk cheese? • Gouda, E. coli O157:H7, > 60-day aged . 2002, Canada: 13 cases . 2010, US: 38 cases E. coli O157:H7; also tested positive for Listeria monocytogenes . 2013, Canada: 22 cases • Several artisan cheeses, 2010, US, E. coli O157 • Creamy Cheddar, 2013 E. coli 103, 3 cases • Reblochon, 2018, E. coli O126, France, 14 children • Soft cheese, multiple outbreaks, Listeria monocytogenes, Salmonella, Campylobacter

22 What are the risks: Pathogens Behavior in Cheese • During cheese making process . Pathogens in raw milk can grow and/or concentrate in curd . 10 to 100 x higher levels in the curd than in raw milk

23 23 What are the risks: Pathogens Behavior in Cheese

• During ripening and storage . Hard/semi-hard cheese: Pathogens are inactivated • Listeria (up to 20 months in Cheddar held at 45°F) • E. coli O157:H7 (160 days in Cheddar; 180 days in Gouda) . Soft/semi-soft cheese: Pathogens may grow • Greater growth near surface of mold-ripened cheese

24 24 E. coli O157:H7 during the aging of Gouda cheese.

Raw milk inoculated with 10 colony forming units per ml 10X increase during make (concentration & growth) 47% moisture; 4.8% salt-in-moisture pH 5.1-5.4

D'Amico, et al., 2010, J. Food Prot. 73:2217-2224 57°F (14°C) for the first 5 weeks and 48°F (9°C) for remainder of the aging period.

* Counts less than enumeration limit but detectable after enrichment25 Infectious dose for E. coli O157:H7 ~10 cells; after 60 days get about 100-300 cells per 1 oz. serving Why does aging alone work (or not work)? • Depends on cheese type and pathogen • Need to kill low-infectious dose pathogens, not just prevent growth • Killing pathogens in cheese requires critical combinations of . “Available” moisture: function of moisture, salt . pH, acid type . Starter culture activity/competitive microflora . Ripening Temperature . Sufficient time for inactivation 26 What Preventive Controls can be used for “raw” milk cheese? Healthy herds Milk quality and facility hygiene

Keep them out

Control formulation Reduce levels of Food (moisture, salt, pH) contamination by and storage validated treatment Safety temperatures Plan Kill all you Keep them can from growing

Combination of moderate heat treatment and aging (hard cheeses) 27 Heat Treatments of Milk for Cheese • Raw milk: not been heated beyond 40°C (104°F)

• “Legal” pasteurization: heat every particle of milk, in properly designed and operated equipment, to a specific temperature for a set amount of time. . Destroys vegetative pathogens and many spoilage microbes . 72ºC (161ºF), 15 s 28 . 63ºC (145ºF), 30 min Heat Treatments of Milk for Cheese • Thermized milk for cheese . Below pasteurization temperatures • 145–149 °F (63–65 °C) for 15 seconds . Not technically raw, but is technically unpasteurized. . Reduces heat-sensitive pathogens . Other heat-resistant beneficial microbes may survive • Pathogen inactivation will continue during aging of hard cheese • Heating of milk does not necessarily have to be conducted in sealed/timed equipment to be effective, but must be controlled 29 How much heat is needed to be “safe” • Target: reduce disease-causing bacteria by 100,000 times . 5-”log” (logarithmic) reduction . 99.999% kill . Less kill (such as 3-log reduction) may be sufficient if combined with other validated controls • Example: . Start: 10 cells per milliliter . End: 1 cell per 10 liters of milk Moderate Heat

30 Is heat pasteurization the only way to make cheese safe? • “Legal” pasteurization is the most reliable method . Other antimicrobials, such as hydrogen peroxide, can reduce Listeria in milk, but need studies on effect on cheese (JDS 2018) . High pressure pasteurization expensive and available equipment limited • Sub-pasteurization could be sufficient if combined with other validated strategies • Need to identify risks and validate process

preventive controls for food safety plan 31 How do you validate preventive controls? • Provide scientific basis that preventive controls will work as intended • May include: . Using scientific principles and data; expert opinion . Conducting in-plant observations or tests . *Challenging the process at the limits of operating controls

32 Validating the Effect of Sub-pasteurization

• Schlesser, 2006 . HTST sub-pasteurization at 148F (64.4C), 17.5 sec • Reduced E. coli O157:H7 to less than detectable limits . No other temperatures tested . Did not make cheese to confirm that no survivors were present

33 What do we need for validation? • Technical data on killing rates of different pathogens at several temperatures to create a flexible process • Data can help answer questions: . What is the minimum temperature I need heat the milk? . How much time is needed at that temperature? . If I bring up the temperature slowly to xx°F and then slowly cool, will I kill “enough” cells?

34 What technical data is needed?

. D-values “death time” • Time to kill 90% of cells (1-log reduction; factor of 10) • Example:

•If D-value150F = 1 minute for 1 log reduction (90% kill) •Heat at 150°F for 5 minutes = 5-log reduction (99.999% kill) . Determined in specialized laboratory • Heat small volumes of inoculated milk at target temperature for different times • Count surviving cells • Mathematic calculation to determine D-values 35 What technical data is needed?

. Z-values • Change in temperature that affects D-value by factor of 10 • Calculated by comparing data from D-values at 3-5 different temperatures • Example: Temperature D-value (°F) (minutes) Z-value = 10°F • 140 12.2 150 1.2 160 0.13

36 What can we do if we collect the right data? . Use data in a “process lethality” spreadsheet (Excel) • Need appropriate D-value, Z-value from lab • Need temperature profile from cheese maker . Can customize heating process based on: • Equipment • Milk type (fat) used • Target microbe to destroy • Desired cheese type . Longer time with lower temperature or shorter

time with higher temperature 37 What can we do if we collect the right data?

Example 1 Reference Temp 150 ºF D value = 1.0 min 175 Milk temperature z value = 10 ºF

150 Start temp 40 ºF 125 Kill zone Maximum temp 145 ºF Hold time @ max 6 min 100 End temp 110 ºF

Temperature (F) Temperature 75 Entire process 20 min

50 Log kill 2.4 log

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0 0 5 10 15 20 25 Time (min) Record temperature every minute

38 For illustration purposes only. DO NOT USE FOR VALIDATION What can we do if we collect the right data? Example 2

Milk temperature 175 Reference Temp 150 ºF D value = 1.0 min 150 z value = 10 ºF 125 Kill zone Start temp 40 ºF 100 Maximum temp 153 ºF 75 Hold time @ max 1 min Temperature(F) End temp 110 ºF 50 Entire process 20 min 25 Log kill 4.9 log

0 0 5 10 15 20 Time (min) Record temperature every minute 39 For illustration purposes only. DO NOT USE FOR VALIDATION How much kill is needed? • Depends on . Type of pathogen (infectious dose) . Type of cheese • Moisture • pH • Acid type • Salt content • Starter culture activity . Time/temperature conditions for ripening/aging • Requires other process controls for formulation and storage 40 Who can generate these data? • Conducted in a qualified laboratory with pathogens . Challenge studies are conducted in laboratories other than those used for routine microbiological testing • Mimic route of contamination, food composition, processing conditions, temperature/time conditions . Account for variability among processes and formulations . Results are applicable ONLY to conditions tested . Test “worst case” scenario • Requires substantial investment of resources (time and money) . Pool resources for challenge studies that affect many 41 small companies What research is needed? (Prioritized) 1. Create d- and z- values for heat-treated milk a. Salmonella, Shiga-toxin producing E. coli b. Listeria monocytogenes, S. aureus 2. Identify inactivation during production and ripening using heat-treated milk a. Hard cheeses • Cheddar-Style (lactic acid predominant) • Swiss-Style (propionic acid predominant) b. Semi-Hard • Gouda (associated with outbreaks) c. Soft/ mold-ripened cheese

42 What research is needed?

3. Surrogates for in-plant testing during ripening a. No surrogates have been scientifically validated for use in cheese • 200 Pediococcus acidilactici meat starter culture validated only for turkey jerky, but worth considering • Similar inactivation as for Listeria and Salmonella • Surrogate was more stable E. coli O157

43 What could be the outcome of the research? • Develop a program (“app”) for use by cheese makers, consultants . Enter appropriate laboratory thermal inactivation data . Enter temperature profile (including the time at each temperature) . Output: lethality (log reduction) of target pathogen • Identify what combinations of heat-treatments and/or cheese “formulation”/aging are sufficient to provide margin of safety

44 What are the responsibilities of the cheesemaker? • The Food Safety Plan is specific to a facility and product • Common components . Identify risks . Identify preventive controls and appropriate monitoring programs . Use milk of good hygienic quality and sanitation practices . Monitor temperatures and times throughout the process • Thermal inactivation, culturing, storage temperature . Monitor starter culture activity and other appropriate compositional attributes (moisture, pH, salt) . Prevent post-process contamination . Verify accuracy of thermometers . Keep records for all process controls 45 Summary • 60 day aging (alone) of raw milk cheese may be insufficient for safety, particularly if low infectious dose pathogens are present • Improve safety by coupling with mild-moderate heat treatment of milk to reduce pathogen levels . Other benefits: may results in more consistent quality of cheese • Laboratory research needed to identify inactivation rates . Data can be used to develop flexible heating process . Cheese makers will need to verify heating rate and temperatures have been met for each batch . Need validate pathogen inactivation in specific cheese types • Implementing process controls will result in a safe, high-quality cheese

46 Thank you for your attention.

Contact: [email protected]

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