Food Protection Trends - May/June 2020 - 207

TABLE 1. Different types of microorganisms used for different types of testing
Type of Microbiological Testing
Validation of a process preventive control

Surrogate Organism

Indicator Organism

Pathogen

+
(in manufacturing facility)

+
(in laboratory)

+
+
+

Verification of a supply chain preventive control
Verification of a process preventive controls
Verification of sanitation controls

the manufacturer (or a third party) performing periodic microbiological testing of an ingredient.
It is also possible that the microbial hazard will be controlled
by subsequent validated processing steps performed by the
manufacturer (e.g., a cook step). It is not necessary to test an
ingredient if a subsequent step will eliminate a pathogen or
if pathogens are never found in an ingredient (such as an oil
or sweetener). For example, it is not necessary to use microbiological testing to verify that tahini used to manufacture
hummus is free of Salmonella if the hummus is HPP-treated
after packaging.
Supply verification requires communication and coordination between the supplier and purchaser. Fabien Robert
(Nestlé) discussed how a large global food company (Nestlé)
partners with its suppliers to help them supply products that
meet Nestlé's microbiological specifications. Nestlé uses several strategies to build food safety awareness with its partners
across the supply chain. The company freely disseminates documents describing best practices (e.g., "Guidance to minimize
microbiological risk - washing produce") to its suppliers and
others. Prevention plans for Nestlé's suppliers are developed
through continuous reviews, vulnerability assessments, and
mitigation plans. By engaging upstream (starting in the field,
if necessary) with its partners (its suppliers), microbiological
risks can be better managed.
HOW TO CONDUCT MICROBIOLOGICAL
TESTING
What organism(s) should be tested for?
When developing a food safety plan, the hazard analysis
should identify what pathogens might be hazards associated
with a particular food product or ingredient. Hazard analysis,
according to Wilger, should not be based on customer requirements (although some companies do share their risk assessments with their customers) and needs to be revisited when
changes occur or new information arises. Not all hazards are
immediately apparent. Both intended and unintended uses of
products need to be considered. For example, consumers may
not follow storage directions. Hazards during transportation
need to be considered. Separate hazard analyses should be con-

ducted for a product if it is manufactured at different facilities,
even if the same process is used to make the same product, as
subtle differences that can alter risk may be present.
Appendix 1 "Potential Hazards for Foods and Processes" to
the FDA Draft Guidance for Industry: Hazard Analysis and
Risk-Based Preventive Controls for Human Food (2016) may
be helpful in determining the key hazards, although Jenny
Scott acknowledged that the FDA "created a lot of confusion"
with this guide (which is being revised). She cautioned that
just because something is listed in the guide doesn't mean you
are required to test for it; it is merely a guide. In many cases,
it makes sense to look for other microorganisms instead of or
in addition to the pathogen. The choice of which microorganism to test for depends on the reason for the microbiological
testing (Table 1).
Pamela Wilger discussed the use of surrogate organisms
rather than the pathogen of interest when conducting
validation testing. She defined surrogates as non-pathogenic
organisms that behave similarly to target pathogens within
a particular food matrix and for a particular process (such
as thermal treatments). A surrogate has to be as robust as
the target pathogen in terms of its ability to withstand an
intervention in the specific food product. Surrogate microorganisms are of particular use in process validation studies
when the validation work is being performed in the actual
food manufacturing facility.
Indicator organisms, which are commonly used to signal
the potential presence of food safety-related pathogens in
an environment, ingredient, or product, are generally more
commonly encountered and are non-pathogenic. Although
sampling may miss pathogens themselves (because their
presence is infrequent and not uniformly distributed), it may
find indicator organisms. Wilger explained that because they
are more likely to be found, indicator organisms can be quantified and used to monitor trends indicating possible control
problems. In choosing an indicator organism, it is important
to consider what potential pathogens might be present and
which indicator organisms are appropriate signals for the
possible presence of those pathogens. She illustrated with a
Venn diagram (Fig. 5) how testing for total Enterobacteriaceae

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