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Hygiene is a vital component in securing food safety, finds Michelle Knott
FOOD safety is a hot topic, with the
EU’s Rapid Alert System for Food and
Feed issuing over 3,500
contamination notices in 2012. Of
course, the number of contamination
incidents within the European snacks
industry is relatively modest
compared with high-risk sectors such
as meat and dairy, but it’s an area
that no food industry operator can
Food safety involves getting a
whole series of steps right, from
sourcing, sorting and processing to
packaging and storage. Cleaning and
hygiene are crucial steps on the path
to a safe product, which is why they
feature prominently in guidance from
the likes of the Global Food Safety
Initiative (GFSI) and the British Retail
Consortium’s (BRC’s) Global
There is also a growing
recognition that good hygiene should
be designed into manufacturing
facilities at an early stage, rather than
expecting cleaning regimes to do all
the work. “There is a general
movement towards placing more
emphasis on the prerequisites of good
hygiene with good factory design and
infrastructure,” says John Holah,
head of food hygiene at Campden BRI.
Established standards are already
driving this trend, such as ISO 22000
and its companion standard PD
ISO/TS 22002-1:2009, which lay out
detailed requirements for hygiene
prerequisites, from building
construction and layout to pest
control and personnel hygiene. “Some
aspects such as waste management
and pest control are important but
they’re not major sources of
contamination,” says Holah. “Proper
segregation and controlling the flow
and behaviour of people are the most
important things.”
Linda Harris specialises in
microbial food safety at the University
of California Davis and has also
advised the United Nations Food and
‘In recent years, contamination
with Salmonella has been found in
almonds, cashews, pistachios, pine
nuts, Brazil nuts, macadamia nuts
and walnuts, among other types of
tree nuts destined for human
consumption.’ Center for Food
Safety and Applied Nutrition, FDA
Agriculture Organization’s
Emergency Prevention System
(EMPRES) on nut safety. She agrees
that Good Manufacturing Practices
(GMPs) are needed to eliminate the
potential for incoming materials to recontaminate finished product:
“Facility design, product flow
(separation of raw from finished
product), equipment and facility
maintenance, cleaning and sanitation,
as well as human hygiene should be
adequately controlled to prevent
Harris adds that nuts raise a
particular issue. “In low-moisture
foods the water activity (available
moisture) is too low to support
microbial growth. For example, the
water activity in tree nuts is generally
less than 0.7. However, it is
increasingly recognised that many
foodborne pathogens, including
Salmonella and EHEC
[enterohemorrhagic Escherichia coli],
can cause illness when present at very
low levels.” In other words, the bugs
don’t need to be growing to make
people sick.
“To-date, most outbreaks
associated with low-moisture foods
have been linked to Salmonella.
However, in 2011, there was an
outbreak of EHEC-associated illness
from consumption of in-shell
hazelnuts, as well as an outbreak
potentially linked to the consumption
of walnuts.”
While the European General Food
Law (Regulation (EC)178/2002) says
that food businesses must ensure
their products are safe, there is no
specific requirement for nut
pasteurisation. In the USA, only
almonds are regulated. Since the
Almond Board of California (ABC)
introduced a mandatory, 5log10 kill
step in 2007, almonds have been the
only nut in the North American
market that have not been subject to a
product recall, according to Cameon
Ivarsson, scientific director for steam
pasteurisation specialist Napasol.
“Things may be changing in the USA,
where FDA is conducting a risk
assessment on nuts with the potential
for issuing guidance or regulating
the industry,” she says.
Ivarsson adds that some progress
is industry-led, rather than driven by
regulation: “Product recall and
litigation costs in the case of food
borne illness outbreaks can range
from $10 million to $100 million in
the USA, prompting major companies
and big brands to move towards
pasteurisation to eliminate the risk.”
“The most common method for
reducing pathogens in tree nuts is the
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application of heat,” says Harris.
“However, thermal processes
previously validated in moist foods do
not apply to nuts. Salmonella and
EHEC have been shown to be more
resistant to heat when they are
present in or within a dry food
environment - in most cases orders of
magnitude more heat resistant.”
In the USA there is also the option
of chemical fumigation with
propylene oxide, but this is banned in
Ivarsson confirms that achieving
effective pasteurisation is not
straightforward: “Dry heat is not very
efficient in eliminating pathogens
such as Salmonella in low moisture
foods. In order to achieve the 5log10
reduction performance criterion set
[by ABC] for almonds, the nuts may
be over-roasted, which is detrimental
to the quality of the product.”
Napasol’s answer is to use dry,
saturated steam and add
pressurisation into the mix to reach
the 5log10 reduction target at
relatively low temperatures. “The
Napasol Statisol technology combines
a tempering phase followed by
pasteurisation and a cooling phase.
Saturated steam conditions are
controlled in a pressurised vessel in
which the products, loaded in bulk
bins, are exposed to the steam. No
drying is necessary,” says
Nuts may be a special case,
but microbiological safety is
a key target for any hygiene
programme. Maintaining
effective segregation
between the raw, “wet” end
of a potato processing line
and post-cooking operations
is vital, for instance.
However, even the most
hygienically designed
facility will require regular
cleaning and disinfection to
keep the bug population
under control.
Unfortunately, the arms
race against pathogenic
bacteria can never been
considered “won”. For
example, Listeria
monocytogenes strains have
been evolving resistance to
some of the quaternary ammonium
compounds commonly used for
sanitation, including benzalkonium
chloride (BC). Between 10 and 46% of
the L. monocytogenes strains isolated
from food processing environments
are regarded as BC tolerant,
according to recent reports. Cleaning
and sanitation technologies will also
have to evolve to tackle such
Holah says that whole room
disinfection is one approach that has
arrived on the scene in the past
decade with the potential to make a
big impact on the bug population.
Whole-room disinfection floods the
entire space with powerful oxidisers
such as ozone or hydrogen peroxide
vapour. Research completed by
Campden BRI in 2010 found that
conventional chemical fogging
reduced airborne microbial
populations and the numbers of
attached microorganisms on
horizontal surfaces but had
minimal effect on bacteria numbers
on vertical surfaces and beneath
equipment. In contrast, ozone and
hydrogen peroxide penetrated
every surface and succeeded in
tackling microbes throughout the
treated area.
“[In conventional cleaning
regimes] we may clean the high
walls and overheads of a factory
once a month. That’s enough
99.99% of the time but it doesn’t
sterilise the environment and
eliminate bugs from the space.
Over time each factory will develop
its own microflora and that may
include Listeria, Salmonella or
other pathogens,” says Holah.
Left: Eco-Lab’s Exelerate ZTF cleaning
programme cuts through deposits
Right: Hygiena’s swabs help validate cleaning processes
Factories could tackle these
persistent organisms using whole
room disinfection every few weeks or
months using a high concentration of
the active agent. Alternatively, ozone
or hydrogen peroxide sterilisation
might be incorporated at a lower
concentration into an everyday
cleaning regime, enabling the factory
to eliminate a stage of chemical
disinfection. “There are factories that
have undertaken this approach and
are successfully controlling food
contact surfaces. There’s also some
evidence that they may be controlling
the environment a bit better too,” he
The research carried out by bodies
such as Campden has since been
picked up by cleaning firms. For
example, Dow Microbial Control
announced last summer that it was
launching whole room disinfection
commercially, with its ozone-based
AOS Certified Technology.
“This is an ozone-based system
that essentially turns air and water
into a powerful sanitizer to control
surface and airborne pathogens,” says
Tony Reed, business development
manager for food safety. “Dow
believes food companies want extra
sanitisation steps to account for
potential gaps left by existing
processes; the threats of
contamination are simply too great.
Ozone is among the most powerful
oxidising reagents available in the
food industry. Our system uses ozone
in vapour form to penetrate hidden
areas and corners, even the
underside of drains.”
The sanitising vapour fully
dissipates afterwards, leaving no
condensation or residue. This makes
it effective even in dry environments
such as bakeries and snack factories.
In practice, AOS Certified
Technology is used in an enclosed
room that’s been cleared of workers.
Each system is custom designed to
suit the space, typically ranging
from 100m3 to 3,500m3. “Every food
production area is unique,” says
Reed. “Dow custom designs and
installs our technology to meet the
specific needs and challenges of our
customers’ operating environment.”
Back at Campden, Danny Bayliss
is carrying out research into a
possible disinfection technology for
the future - the use of cold plasmas.
“A plasma state can be achieved
when enough energy is applied to a
gas. For the generation of cold
plasmas electrical energy is typically
used rather than applying heat,” he
Applying a voltage to a gas
generates an electric field that can
accelerate any free electrons, which
will collide with neutral gas atoms
and generate reactive plasma
species, including electrons, ions,
atoms, free radicals and UV photons.
“Many of these gas species have
the ability on their own to inactivate
a wide range of pathogenic and
spoilage organisms,” says Bayliss.
“When the electrical supply is
switched off the reactive species will
return to back to their neutral
ground state.”
He says that some companies are
already exploring the ability of
plasmas to clean the air throughout
a working day, and there are claims
that they can have antimicrobial
effects on surfaces. “One such
example might be the treatment of a
conveyor belt material during
production. This could help reduce
contamination on the belt and
inactivate bacteria before they have
chance to establish biofilms. This
online type of treatment could
potentially extend production runs
between scheduled deep cleans,” says
The work at Campden currently
focuses on lab-scale feasibility
studies but some companies are
already working to develop
proprietary commercial systems,
according to Bayliss.
With the rise of allergies and today’s
“free from” product ranges, cross
contamination is the other important
issue for cleaning. In fact, there are
no standards requiring the
reduction of potentially allergenic
residues to below a specific level.
Instead, the consensus is that good
cleaning should remove allergens
provided it’s effectively removing
other food debris. The important
thing is therefore to validate the
efficacy of the overall cleaning
Hygiena International offers a
range of different tests that can
For example, the company’s
SuperSnap swabs rely on ATP
bioluminescence to check for
biological contamination. ATP is
present in all living cells, so the wellestablished conventional technique
draws no distinction between, say,
food debris or bacteria. However, it’s
extremely easy and quick, with
results in just 15 seconds.
Meanwhile AllerSnap is
Hygiena’s non-specific protein test,
which takes 30 minutes at 37oC to
detect levels of protein down as low
as three micrograms in a standard
According to general manager
Martin Easter, combining these two
tests provides a “belt and braces”
approach that is more useful in
practice than trying to detect a
specific protein such as gluten: “How
much in a food residue is ATP,
protein or allergenic protein? You’re
looking at smaller and smaller
fractions of the whole [as tests
become more specific] and the
target becomes more difficult to
detect. Allergens are mainly
glycoproteins anyway and it’s much
easier and quicker to measure all
For companies worried about the
presence of specific problem bacteria,
the latest addition to the Hygiena
arsenal is MicroSnap, which uses an
ingenious variation on the ATP
technique to detect the presence of a
particular pathogen. The test takes
around seven hours.
STICKY problems
In terms of removing residues, the toughest area of
the factory for many snacks manufacturers is the
area in and around the fryer, especially now that the
use of high-oleic oils is the norm across Europe.
These oils are great for consumers, bringing down
the level of saturated fats in snack products.
However, they are also vulnerable to polymerisation,
making them more prone than traditional oils to
creating sticky, hard-to-shift deposits in and around
Cleaning and hygiene specialist Ecolab has
come up with a system aimed specifically at
mitigating the impact of these deposits on the
cleaning regime. Its Exelerate ZTF cleaning
programme can reduce the total cost of cleaning by
between 28 and 60%, depending how the fryer is set
up, according to Adrian Müller, marketing manager in
Ecolab’s Food & Beverage Division. The savings result
from reducing the consumption of water, energy and
chemicals, as well as the time taken for a full clean
down incorporating boil-out of the fryer.
The main step within the cleaning programme
that results in these benefits is a pre-cleaning stage
that uses a mobile delivery system with a special
nozzle to apply a thixotropic gel to any deposits. “The
thixotropic gel structure supports the cling time and
prolongs the contact time on surfaces. That’s really
important because the polymerised residues are
quite sticky and hard to remove. It supports the
penetration and the wetting of the residue,” says
It’s the combination of the clinging gel
structure, the application mechanism (which
optimises the amount of cleaning agent applied) and
the chemistry of the Exelerate ZTF gels that together
deliver the wider benefits.