In-house Testing: An Aid to Good Practices

Dennis D’Amico, Ph.D.

University of Vermont and the Vermont Institute for

Artisan Cheese

3M Microbiology

• Primary production: influence on quality or safety • Examples: water, milking equip., pipelines, etc.

• Ingredients: verify acceptability of an ingredient

• Examples: milk, spices, rennet, etc.

• In-Process: verify the process is functioning as

intended or contamination is not occurring • Examples: quantifying Staph. aureus levels, coliforms, etc.

What to test?

Swanson, K.M.J. (Ecolab). 2009. Useful Testing in Food Safety Management. ICMSF Recommendations

• Processing Environment: • verify effectiveness of prerequisite programs (PRPs: GMPs,

sanitation, etc.) to reduce risk of cross-contamination; • promote knowledge and awareness of the environment

and conditions that could result in product contamination; • seek out harborages and growth niches

• Examples: • Air sampling • Swab/sponge samples of equipment, employee hands,

aprons, etc.

What to test?

Swanson, K.M.J. (Ecolab). 2009. Useful Testing in Food Safety Management. ICMSF Recommendations

• Utility: Spoilage, ↓ shelf life, no health concerns • Total aerobic bacteria, yeast + mold, etc.

• Indicator: Verify efficacy of PRPs • Coliforms + E. coli • Enterobacteriaceae: indicator of possible presence of

Salmonella, Yersinia, Klebsiella, Shigella spp., etc.

• Moderate hazards: Staphylococcus aureus • Not life threatening, short illness duration, self limiting

• DO NOT TEST FOR OTHER PATHOGENS IN-HOUSE

Target organisms

Swanson, K.M.J. (Ecolab). 2009. Useful Testing in Food Safety Management. ICMSF Recommendations

In-house testing

• When possible, testing should be conducted by properly trained individuals

• Proper techniques must be followed to prevent:

– error and/or contamination of testing materials

– cross-contamination in facility and possible illness

• Microbiological labs should be in a separate building

• If not, should be as far away from processing areas as possible with proper air handling and filtration

– Ideally lab would be under negative air pressure

Testing materials

• Sterile bags for solid foods

• Sterile vials for liquid collection

• Sterile diluent (for dilutions)

• Sterile droppers or pipette and sterile tips

3M Microbiology

• Best for small areas (ex. 100cm2) • “nooks and crannies”

• Pre-measured fill volumes for quantitative use • add 1ml of solution to plate for enumeration

Sampling swabs

3M Microbiology

• Best for larger areas (ex. 4 ft2) • Hydrated sponge with sterile gloves

• Not very user friendly, need to change gloves • Risk of contamination • More sponge surface area

• Hydrated sponge with plastic handle • Reaches high ceilings, down drains, etc. • return the sponge to bag and snap off handle; no need for gloves

• Liquid eluted can be plated for analysis

Sampling sponges

3M Microbiology

• IDEXX Colilert for coliforms/E. coli in water

• 3M™ Petrifilm™ Plates

– Aerobic Count, Coliform/E. coli Count

– Enterobacteriaciae Count Plates

– Yeast and Mold, Staph Express Count

• Easygel® Media

– Coliscan Plus, Mold test, Total Count T-salt

Testing media

• Purchase: (examples) – Hova-Bator Incubator ($40) – Nelson Jameson Compact ($80)

• Or build your own: 1. Aquarium, heavyweight plastic,

Coolers, or Wood 2. Thermometer 3. Heat tape or light bulb (75w) 4. Optional: dimmer, thermostat

Incubators

• Liquids: Milk, whey, etc. • collected aseptically in a sterile vial

• Solids: Cheese, curds, spices, etc. • aseptically w/ sanitized knife, trier, etc. and sterile bag

• Air: • open Easygel dish, hydrated Petrifilm

Samples/Sampling

• Environmental samples: equipment, hands, etc. • Systematic sampling technique and protocol:

• location, size, direction, etc.

Sampling patterns

Image: http://www.cemag.us/article/how-succeed-search-nothing-effective-swabbing-techniques-cleaning-validation?page=0,1

Samples/Sampling

• Templates to define specific area are available

• Petrifilm can be used as contact plates

• Example: Quickswab

Plating (liquid)

Plating (solids)

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3M Microbiology Sample Preparation Guide

Counting + Dilutions

Counting + Dilutions • Goal is to get between 20-200 colonies per plate

• Dilution = sample / sample + diluent

– 1ml / 1ml + 9ml = 1/10 or 1:10 (11g→99ml)

NOTE: A new, sterile pipette is needed for each transfer!

• Counts in food samples: • Targets for some tests are available

• Ex. Total bacteria, Staph counts in milk • Most vary between plants; base goals on historical data

• Food contact surface environmental samples: • Coliforms, E. coli, Enterobacteriaciae, and yeast and

mold are sensitive to sanitizers and should be absent: • <10 CFU/sponge or 1ft2

• Aerobic plate count: • <100-1000 CFU/sponge or 1ft2

What do numbers mean?

Kornacki, J. 2011. Indicator organism Assays: Chaos, confusion and criteria. Food Safety Magazine.

Disposal • Disinfect all contaminated materials:

– Pressure cooker: cook at 15 lbs. for 15 minutes

– Boil for 45+ minutes

– Bleach:

• Place 5 ml of straight bleach onto the surface of the Easygel medium, let sit for ≥5 minutes

• Saturate and soak Petrifilm at least 1hr or overnight in 20% bleach solution

Manufacturer recommendations (3M and EasyGel )

Resources

• Full descriptions on how to use the products can be found on the 3M website: – http://solutions.3m.com/wps/portal/3M/en_US/Microbiology/F

oodSafety/industries/one/ – Just click on the product you want, then click the resources tab.

• The info you need is listed under the data sheet section. • This link might take you to an example

– http://solutions.3m.com/wps/portal/3M/en_US/Microbiology/FoodSafety/product-information/product-catalog/?PC_7_RJH9U523003DC023S7P92O3O87000000_nid=PM3VW0J710be29BDXSBJ7Fgl

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3M Microbiology

• DISCLAIMER: The information provided during the training seminar and in the related materials is for informational purposes only, the American Cheese Society and the Vermont Institute for Artisan Cheese and their respective members (the “Sponsors”) make no representation or warranty with respect to the completeness, accuracy, reliability, or suitability of any information provided in training sessions or materials. We recommend that participants consult an attorney concerning the laws applicable to any particular situation. By attending the workshop or utilizing the materials provided in the workshop, you agree to release the Sponsors from any and all liability that may result from your use of the information provided in the training sessions or materials.