By Jeffrey L. Kornacki, Ph.D.
The Missing Element
in Microbiological Food
Approaches, Part 2
Recent and past experiences involving
contamination of foods with unex-
pected microbes indicate the need for
enhanced approaches to microbiologi-
cal food safety. The purpose of food
safety programs should be to keep
harmful agents such as chemicals, allergens, extraneous matter
(insects, metal filings, rubber, plastic, etc.) and microbes out of the
Part 1 of this article revealed the need for walk-through microbiological risk assessments as a critical supplement to food safety and quality systems assessments.
This approach can be applied to both one’s own facility and those providing ingredients that may pose microbiological concerns in the finished product. These assessments may be conducted by outside third parties or in-house experts. A
combination of both is recommended.
In-plant Microbiological Risk Assessments
This type of risk assessment is quite
different from the type that is often discussed in academic circles. It has little to
do with statistics and probability, but
everything to do with observations in the
plant related to where microbes have
grown in localized “niches.” It is certainly
impractical, and likely impossible, to expect food-processing facilities to be sterile. However, microbial growth in
processing facilities can be controlled.
Microbial growth niches occur when
moisture, nutrition, time and growth-conducive temperatures occur in a non-sterile environment (Figure 1). Adequate
nutrition for microbial growth is typically in abundance in food-processing
environments. Even dust particles may
contain enough nutrition to grow microbes to high numbers in small volumes of fluid or localized moist areas.
Time abounds, particularly in areas
missed or inaccessible for cleaning. Microbial growth can occur over a wide
range of temperatures between approximately 32 and 140 °F, readily found in
most processing environments. Moisture
is absolutely necessary for microbial
growth; hence, its control is essential.
Sites with likely microbial growth are
those in which moisture is entrapped
(e.g., wet insulation, roof leaks, water
marks, hollow conveyor rollers, duct-taped pipe leaks, sandwiched areas associated with equipment such as slicers,
conveyor guides, product scrapers, etc.).
A list of sites related to Listeria niches is
found in Kornacki and Gurtler.1
Gabis and Faust2 wrote that “the
probability of product contamination
from the environment is dependent
upon a number of variables.” They then
listed those as follows:
• Proximity of microbial growth niches
to the product stream
• Number of niches in the food-processing facility
• Spatial relationships of niches and
the product stream
• Microbial population in niches
• Degree of niche disruption during
• Exposure of the product stream to
Those variables can then be applied
to the assignment of relative risk associated with sites throughout the plant.
Figure 1: Microbial Growth Requirements
Prioritization of Risk
Associated with Specific Sites
The walk-through microbiological
risk assessment should focus on observing and sampling sites conducive to
growth. These sites can be broken down