IBP NEWS
ULTIMATELY HYGIENIC
REDUCED BIOFILM FORMATION IN TUNNEL PASTEURISERS
THANKS TO ANOLYTE
The Goal: Reducing
Germs in the Product
Without Altering its
Flavour The process water in the tunnel
pasteuriser’s heating and cooling zones
requires special attention and treatment
with regard to hygiene and biofilm
formation: through innovative and
contemporary gentle water disinfection,
Innowatech sets new hygiene standards.

Anolyte as hygienic solution in the
tunnel pasteuriser: this pH-neutral
disinfectant inhibits high proliferation
rates of germs in the process water even
at extremely low concentrations and
thus also prevents biofilm formation.

The active ingredient, produced in-situ
from sodium chloride and water
through membrane cell electrolysis,
replaces aggressive, off-gassing and
expensive disinfectants.

Pasteurisation is the safest way to
preserve food and drinks in jars, cans
or bottles. That’s what the textbooks
say. And brewers and maltsters know
that this rule applies all the more
when beverages contain fermentable
substances. Large breweries with high
output, which produce for the European
and global markets, in particular, rely
on the tunnel pasteuriser.

Pasteurising beer can significantly
extend its shelf life and thus facilitate
longer transport routes to the retailer.

14 A conveyor belt feeds
the filled and sealed
bottles at an inlet
temperature of 8 to 10
°C into the pasteuriser.

The pasteuriser
features various
temperature zones in
which the bottles and
the product they contain are gradually
heated (40, 50, 60, 75°C). To this end, the
bottles are constantly sprayed with hot
water distributed by nozzles and heated
until the pasteurisation temperature of
ca. 60 to 75°C has been reached.

The bottles stay in this zone for 10
to 30 minutes.

Pasteurisation reduces the
microorganism count in beer, other
beverages and food, and thus extends
the products’ shelf life. When it comes
to taste, odour, turbidity and colour, it
is necessary to gently heat the products
to preserve high quality. This is why
re-cooling takes place across several
temperature zones in order to maintain
high beverage quality and avoid the risk
of glass breakage.

The process heat, which is usually
generated by hot steam, is derived from
the water by a plate heat exchanger
during re-cooling and fed back into the
heating process.

This facilitates a high level of heat
recovery. A tunnel pasteuriser is thus a
seemingly simple, albeit a highly
complex machine. Apart from beer, the
process is also perfect for fruit juices,
carbonated beverages and canned food.

The Challenge of Microbiology
In a brewery’s bottling hall, a tunnel
pasteuriser takes up a lot of space and
is striking just by this. Maintaining
microbiologically flawless water
quality in the pasteuriser`s heating
and cooling zones constitutes a major
challenge for its owner. Various germs
will find ideal habitat conditions in the
temperature zones ranging from 25 to
55°C. In addition to warmth and water,
also sufficient nutrients, introduced
through product residues on the
bottles or through glass splinters, are
available. However, nutrients contained
in the beverages and foods are not only
tasty for humans, but also facilitate
rapid, sometimes even unrestrained,
proliferation of microorganisms. As a
result, more and more biofilm is formed
on the constantly wet inner surfaces of
the pasteuriser.

Especially where the biofilm cannot
be mechanically removed by spray
nozzles, a slimy layer forms over time.

Due to the warmth, it may virtually
cake on the surface and make cleaning
significantly more difficult.

Chemical Treatment with
Biocides and Inhibitors
To counteract the contamination, the
process water is treated with various,
usually organic, biocides. The process
water in the pasteuriser is also
treated with chlorine dioxide. Since
almost all biocides have a corrosive
effect, corrosion inhibitors as well as
– depending on the water hardness –
hardness stabilizers need to be added
to the water.

Organic biocides are supplied
in concentrated form in canisters,
barrels and containers, are often very
expensive and usually only effective in
high concentrations. They are classified
as hazardous substances that make
INTERNATIONAL BOTTLER & PACKER | JUNE 2025



NEWS
carefulness essential when people are
working at the pasteuriser and that may
only be transported and connected by
trained employees wearing appropriate
protective equipment.

Alternatively – although this is
not a good idea –chlorine dioxide is
used to combat the biofilm. As is well
known, chlorine dioxide evaporates at
temperatures of around 32°C and quickly
corrodes all metals nearby, including the
st. st. housing of the tunnel pasteuriser.

This can lead to significantly increased
cleaning needs and a greatly reduced
service life of the system.

Anolyte – The Gentle Alternative
In the summer of 2023, the master
brewers at a major brewery asked
Innowatech’s customer service for
help. The brewery had been using
Innowatech Anolyte® for various
disinfection applications for almost ten
years. Considering the good experiences
made with regard to the disinfection
effect and the easy handling without
any hazardous substances, the
process water treatment in the tunnel
pasteuriser was to be expanded.

However, the biofilm formation
in the approximately three-year-old
pasteuriser (throughput: ca. 50,000
bottles per hour) had increased
significantly in recent months, so that
cleaning was required more and more
frequently. Increasing the amount of
biocide used did not yield the aspired
result but caused new problems with
biological wastewater treatment instead.

Fortunately, the existing Innowatech
Aquadron® system still had capacities
in terms of Anolyte production and
therefore the disinfection of the
pasteuriser’s process water could be
switched to Anolyte at short notice. Due
to the Anolyte’s low active ingredient
concentration at around 500 ppm active
chlorine, all it took was a slightly larger
dosing pump. The control for the active
ingredient dosing was taken from the
existing system.

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The result of using Anolyte: The
high effectiveness against germs
and biofilm already showed after
just one week: the biofilm formation
was significantly reduced. Thanks to
consistent disinfection with Innowatech
Anolyte®, after four weeks almost no
deposits were detectable. For further
optimisation, the two previously used
inhibitors had to be replaced by an
Anolyte-compatible hardness stabiliser.

Uninterrupted Data Collection
Because the process steps in the
pasteuriser’s five heat-up and five
cooling tanks (see diagram) are so
different, the dosing of the active
ingredient concentration needs to
be coordinated in detail. Dosing is
monitored fully automatically by the
Innowatech Multi-Measurement Centre
(MMC). Next to free chlorine and redox,
temperature, conductivity and pH are
measured, evaluated and documented
there. To determine the ideal amount
of biocide, the data are continuously
evaluated, passed on to the control
system and ultimately to the dosing
pumps for dosing. The temperature and
conductivity of the water can also be
used to identify the risk of corrosion in
the tanks. This information is also used
to prevent corrosion in the pasteuriser.

The MMC is also useful when
it comes to treating cooling water
in evaporative coolers. Ongoing
documentation and the uninterrupted
treatment of the cooling water with
Anolyte in
extremely low
concentration (usually
in line the
drinking water
regulations) obviate need
for microbial
counting each two
weeks. Conclusion: Advanced Gentle Water
Treatment and Disinfection
By using anolytes that contain about 80
percent HO-CL, bacteria, viruses and
fungi can reliably be eliminated, which
prevents the formation of biofilm. The
development of resistance is excluded.

The high level of purity and effective
disinfection can even be increased by
using the Innowatech HyCleanConcept
spray systems in bottling plants to
extend the shelf life of beverages.

No hazardous substances handling:
Innowatech Anolyte® is produced just-in-
time from water and a minimal amount
of common salt. It is thermally stable
and of a very low concentration (< 0.2%
active chlorine). Neither the starting
material nor the biocide are hazardous
substances or hazardous to water. The
formation of disinfection by-products
such as THM and chlorate is greatly
reduced or eliminated entirely (chlorite).

Gentle water disinfection by using
Anolyte also has a positive effect on
wastewater treatment and disposal; it
generally does not cause an increase in
AOX, COD, etc.

Last but not least, the cost for
operating the tunnel pasteuriser can be
significantly reduced if there is no need
to constantly buy expensive biocides
and inhibitors. In the specific case
described, this amounts to about EUR
6,000 per year. Cleaning costs and fresh
water consumption are also reduced.

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