Salmonella in low-moisture foods and environments:
challenges and control strategies
Introduction: Food safety
q  The ability of pathogenic microorganism to gain entry into food
supply systems remains a major public health challenge &
concern.
q  Each year, foodborne illness outbreaks affect millions of people
and kill thousands.
q  Tainted food has cost the food industry billions of dollars in
recalls, lost sales and legal expenses.
KANTHA CHANNAIAH AIB INTERNATIONAL Challenges in low moisture foods and environments:
q  Low water activity (aw) processing environments present altogether a different food
safety challenges than those found in higher aw
q  Introduction of water can:
q  Additionally, these outbreaks undermine consumer confidence in
affected products, and diminish market demand.
Common misconception
Low moisture foods (including some bakery products) and
environments are considered to be safe, as they do not support the
growth of microorganisms including harmful pathogens.
q  Cause microbes to multiply fast and contaminate the food products and environments
q  Reduce the shelf life of the finished products
q  Food processing equipment and nonfood-contact surfaces must be cleaned before
sanitation
q  Dry sanitation technique need to be implemented
q  Care should be taken to design new processing equipment or retrofitting may be
employed in case of old equipment
Why Salmonella?
Facts and reality
Research clearly indicates that pathogens, including Salmonella can
survive in adverse conditions such as low moisture environment for a
long time (Hiramatsu et al. 2005; Janning et al. 1994; Juven et al. 1984).
Salmonella outbreaks and illness in the US (1998 – 2007)
q  Leading human foodborne pathogen in the U.S. & around the world
151 outbreaks &
4200 illness
q  Responsible for more deaths than any other known human foodborne
pathogen
q  An estimated 1.2 million cases occur annually in the US
q  Salmonella form biofilms on contact surfaces such as glass, stainless
steel, glazed tile, plastic, and are very resistant to cleaning & sanitation
practices (Corcoran et al. 2013)
Source: Center for science in the public interest, 2009.
1 Factors contributing Salmonella survival:
q  The factors that can cause Salmonella contamination in low-moisture
foods are (but are not limited to)
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poor building and equipment design
poor quality ingredients
poor cleaning and sanitation practices
poor pest management practices
lack of validation etc.
q  The dust in a food plant can act as a source of contamination
q  Salmonella can adapt to extreme environmental conditions such as low
water activity, pH (can survive at pH 3.8 and 9.5 (optimal 6.5 to 7.5))
and varied temperature conditions (2-54ºC (optimal 35-37ºC)).
Sources of Salmonella in a bakery
Flour Cookie dough Nuts Stored insects Egg Spices Salmonella Many of these products are often ingredients in bakery and can consequently drive further recalls of
those products
FDA’s food safety concerns:
q  Salmonella cannot grow in low moisture foods &
environments but, it can survive.
q  Survival can occur for long periods of time
q  Longer shelf life of low moisture foods
q  Increased heat resistance at low moisture
conditions
q  Low numbers of Salmonella can cause illness
q  If low-moisture ingredients or foods are rehydrated
during manufacturing or preparation, then bacteria
grows fast thus increasing the health risk to
consumers
Factors affecting Salmonella survival in food
q  As the water activity (aW) of the products becomes limited, the probability of
Salmonella growth is reduced; however, the ability of the remaining Salmonella
survival is greatly increased.
q  The survival is affected by nutritional composition of the products:
q  Eg: Salmonella showed highest resistance in low water activity and high fat
foods.
q  The location (internal vs external) of Salmonella cells in a product is also
critical for its long term survival.
q  The storage conditions, the strain and serotypes also play an important role in
Salmonella survival for long period in low-moisture foods and in environments
Salmonella in bakery products
q  The U.S. baking industry (approx. ~$30 billion market value per year) traditionally
had a very safe record for the production of shelf stable processed foods
q  Pathogens such as Salmonella spp. can be introduced into bakery products through
a wide range of ingredients such as egg (Board 1969; FSIS 1998), milk products
(El-Gazzar et al. 1992; Ahmad et al. 2000), flour (Richter et al. 1993; Dack 1961),
milk chocolate (D’Aoust 1977), coconut (Goepfert 1980), peanut butter (Scheil et
al. 1998), fruit (Golden et al. 1993), spices (Hara-Kudo et al. 2000) and yeast
flavorings (Joseph et al. 1991)
q  The presence of Salmonella spp. in bakery products could create a public
health risk if the product is improperly baked
The need……….
q  Reducing risks from foodborne pathogens is an essential
part of every food manufacturer's responsibility to protect
both its customers and its business
q  U.S. regulatory agencies instituted ZERO tolerance
standards for pathogens such as Salmonella, E. coli
O157:H7, and Listeria monocytogenes in ready-to-eat
products
q  Since Salmonella are able to persist in low-water activity
foods & processing environments it is vital to employ
mitigation strategies to control Salmonella occurrence
2 How to control Salmonella in low moisture foods and
environments?
Possible entry points of microorganism
q  Consider points of entry for microorganism
q  Understand the factors that influence the survival of Salmonella in lowmoisture food and environments
q  Building and equipment design
q  Effective implementation of preventive controls, prerequisite programs
GMPs, HACCP
q  Inspection and auditing
q  Effective corrective action
q  Process validation or kill-step validation
q Raw materials/ingredients
q Air
q Water
q Personnel
q Contact materials/surfaces
q Pests
Control strategies: Raw materials/Ingredients
q  In most cases ingredients are the primary source of
contamination
q  Ingredients are increasingly being tested by food
processors
and customers
q  In most cases positive finished product tests have led to
positive ingredient tests and recalls
q  Ask for COAs and conduct testing where necessary
Control strategies: Pest management
Control strategies: Effective GMPs
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Personnel practices
Building and equipment design
Production and process controls
Sanitation and cleaning practices
Storage and distribution
Environmental monitoring program (EMP)
q  Pests (insects, birds, rodents etc.) can act as a potential source of contamination
Preventive control:
Environmental Monitoring Program
Why do we need an Environmental
Monitoring Program (EMP)?
q  Microorganisms are generally introduced into the food processing
environment through raw materials, pests, air, water, and employees.
q  If contamination levels are high or sanitation procedures are inadequate,
microorganisms may establish and can contaminate food products,
leading to foodborne illness outbreak.
q  A substantial amount of foodborne illness outbreaks results from poor
environmental controls and/or hygiene practices.
q  Hence, it is critical to maintain and monitor the hygienic environment in
the food processing facility
3 Benefits of EMP
An effective EMP:
q Will measure the overall effectiveness of:
ü  Sanitary design
ü  Personnel practices
ü  Operational methods
q EMP will verify that cleaning and sanitizing procedures are:
q Keeping indicator organisms and any organisms of particular concern
in check
q Will assess the risks posed by pathogen of concern
q Keep in mind that EMP does not make food safe
What is validation?
q  As food safety management moves toward risk-based food management,
food manufacturers will need to provide scientific evidence that their
foods comply with current safety standards
q  A preemptive scientific evaluation providing documentary evidence that
a particular process is capable of consistently delivering a product,
meeting its pre-determined specifications
q  A collection of scientific evidence
q  Often expressed as “log reduction”.
EMP is not designed to validate the effectiveness of cleaning and
sanitizing methods, but is more focused on validating cleaning
and sanitizing frequencies, and all the programs of the Good
Manufacturing Practices (21 CFR).
What FDA FSMA says?
q  E7.1.2 What would constitute validation?
(Proposed § 117.150(a)(2))
The proposed rule would require that the validation of preventive controls
include collecting and evaluating scientific and technical information or, when
such information is not available or is insufficient, conducting studies to
determine whether the preventive controls, when properly implemented, will
effectively control the hazards that are reasonably likely to occur
q  The owner, operator or agent in charge of a facility would need to conduct
controlled scientific studies to establish that a preventive control measure
is adequate to control the hazard………..(78 FR 3753 – 3754)
Benefits of process or kill-step validation:
Scientific validation
is the only way to confirm that a
particular process is consistently
delivering a desired lethal effect
(heat in this case) to ensure the
destruction of pathogenic
microorganisms; often expressed as
"log reduction"
q Pathogen free bakery products assuring greatest safety possible
q Protects consumers, builds confidence and increases demand
q Helps in determining an effective treatment
q Demonstrate compliance with the FDA-FSMA act.
q Can save bakery industries millions of dollars by avoiding recalls
and other legal penalties due to foodborne illness outbreaks
4 q  It's the responsibility of the food manufacturer to make the
finished product safe
q  Salmonella can survive low moisture conditions, and may
grow if the facility is unable to control the introduction of
water.
q  It is important to understand the factors that influence the
survival of Salmonella in low-moisture food and
environments
q  Effective implementation of preventive controls, GMPs,
HACCP plan, and process validation or kill-step validation
is vital to prevent, and to control Salmonella getting into the
finished products
References
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Corcoran. M., Morris. D., Lappe. N. De., O'Connor. J., Lalor. P., Dockery. P., and M. Cormican. 2013 Commonly used disinfectants
fail to eradicate Salmonella enterica biofilm from food contact surface materials. Applied and Environmental Microbiology, 80(4):
1507-1514
CSPI, 2009. Outbreak alert. Analyzing foodborn outbreaks 1998-2007. (Center for science in the public interest, 2009.).
GMA 2009. Control of Salmonella in low-moisture foods
Harvey.R.W.S., and T. H. Price. 1961. An outbreak of salmonella food poisoning attributed to bakers' confectionery. J. Hyg., Camb.
59, 105-108.
Hiramatsu, R., M. Matsumoto, K. Sakae, and Y. Miyazaki. 2005. Ability of Shiga toxin–producing Escherichia coli and Salmonella
spp. to survive in a desiccation model system and in dry foods. Appl. Environ. Microbiol. 71: 6657-6663.
Janning, B., P. H. in’t Veld, S. Notermans, and J. Kramer. 1994. Resistance of bacterial strains to dry conditions: use of anhydrous
silica gel in a desiccation model system. J. Appl. Bacteriol. 77: 319-324.
Juven, B. J., N. A. Cox, J. S. Bailey, J. E. Thomson, O. W. Charles, and J. V. Shutze. 1984. Survival of Salmonella in dry food and
feed.J. Food Prot. 47: 445-448.
Micro facts, 2003. The working companion for food microbiologists, 5th edition by Laurie Curtis and Richard Lawley. Leatherhead
Publishing, Randalls road, Leatherhead, Surrey KT22 7RY, UK.
THANKS
KANTHA CHANNAIAH AIB INTERNATIONAL 5