FoodFood(soil)(soil)

WaterWater TimeTime

Microbial Growth Requirements

organism temperature

FoodFood(soil)(soil)

WaterWater TimeTime

Microbial Growth Microbial Growth RequirementsRequirements

Sleuthing Microbial Growth NichesSleuthing Microbial Growth Niches

• Observe operating practices (if possible), including sanitation

• Maintenance and repair practices

• Equipment design (including modifications)

The Slicer DilemmaThe Slicer DilemmaSausage slicer

?

?

Problem: Daily post-operational swabs of the slicer blade are consistently positive for the presence of Listeria. However,

pre-op swabs and finished product testing always yield negative results. The product is fermented sausage with a pH below

4.0. What is going on, and where should I begin my investigation?

Slicer Investigation BeginsSlicer Investigation Begins

• Observe the process (including sanitation) -Beware of gloves! See if workers and

supervisors understand how to use gloves -Blade sharpening and handling of machine

controls and product -Stoppages and start-ups -Handling of bins and pallets by hand-truckers -Any other actions that may cause

contamination (hand wash stations, aerosols, condensation, hygiene, outerwear, etc.)

More slicer investigationMore slicer investigation

• Observe maintenance practices

-After adjustments, repairs, replacing parts, etc., is the area (including non-product contact surfaces) sanitized efficiently?

-Take operational samples

Check out the Slicer DesignCheck out the Slicer Design

• Maintenance personnel are historians

-Is the machine being used as it should?

-How old is the equipment?

-Has the design been altered? If so, how?

-The most common red flag is neglect

-Old habits die hard

-A new set of eyes

Sleuthing the Slicer ProblemSleuthing the Slicer Problem

• Operating/maintenance procedures and process

-No environmental issues were observed

-Operators switched machines almost on a daily basis

-Sanitation was effective

-Other slicers were OK

-Maintenance practices appeared sound

More SleuthingMore Sleuthing

• Investigating the machine’s design

-Blade housing

Chat With PersonnelChat With Personnel

• QA manager, sanitation engineer and maintenance supervisor agreed that although blade housing is hollow, it is air-tight.

• Experienced maintenance man (the “historian”) reveals that the 30 year old slicer was modified.

• Visual inspection confirms radical changes

Digging InDigging In

• Several new bolts were observed

• Blade was removed showing discolored liquid marks (now dry) on surface of housing

• When bolts were removed brown liquid began to leak from inside housing

• Brown liquid tested positive for presence of Listeria

What Happened?What Happened?

• Over the years, sanitizer, rinse water and food residue entered the hollow blade housing through tiny openings around added bolts

• Conditions inside did not reach kill temperature• Rotation of the blade caused a vacuum and

drew the contaminated liquid out • Original design was altered and system was out

of control

Suggestions: Eliminating the SourceSuggestions: Eliminating the Source

• Options for regaining microbial control

-Purchase new equipment

-Have maintenance department alter bolt holes with filler to prevent leaks

-Drill new drainage holes

-Have machine overhauled

-Alternative heat treatments (need validation)

Summary: Finding The SourceSummary: Finding The Source

• Growth niches are dependent upon nutrients, moisture and time

• Investigations should include observing the operation, maintenance and design

• Paradigms of plant personnel can be very telling (neglect raises red flags, new set of eyes, etc.)

• Veteran maintenance personnel are historians• Use the proper sampling device for the job (food

contact and non-contact surfaces and air)