Listeria Risk in Cold Stores: What Happened When We Introduced Climate Separation?.

In high-risk food environments, few words carry as much weight as Listeria.

For food producers, airline caterers and cold chain operators, it isn’t just a microbiology term, it’s a commercial risk.

Why Listeria Matters in Chilled Environments

Listeriosis is a serious foodborne illness caused by Listeria monocytogenes. Unlike many other bacteria, Listeria can survive and even grow at refrigeration temperatures.

That’s what makes it particularly concerning in chilled food environments.

For businesses, the consequences of contamination can be severe:

• Product recalls
• Production shutdowns
• Deep cleaning programmes
• Retailer penalties
• Contract loss
• Brand damage
• Legal exposure

In sectors like airline catering, where food safety compliance is scrutinised to the highest level, there is very little margin for environmental instability.

Environmental Instability: The Hidden Risk in Chillers

Cold stores and prep chillers operate in demanding conditions:

• Frequent door openings
• Trolley movements
• High staff traffic
• Warm, humid air ingress
• Condensation formation

Every time a door opens, warm external air enters. That air carries moisture. When it meets cold internal surfaces, condensation forms.

Condensation is not just an operational issue, it can become a hygiene concern.

Environmental stability is therefore a cornerstone of risk management.

A Question From an Airline Catering Facility

At a UK airline catering site operated by DO & CO, the team wanted to explore something practical:

If we improve climate separation at the chiller entrance, what impact does that have on monitored hygiene indicators?

Not to prove sterilisation.
Not to claim elimination.
But to observe conditions under controlled operation.

A Thermoscreens air curtain was installed at the chiller entrance.

Trial Structure and Independent Testing

The site carried out a structured trial:

• The chiller was emptied, leaving minimal product inside
• The air curtain operated continuously
• Food samples and environmental swabs were taken
• Samples were sent to Intertek Food (UK) for independent laboratory analysis
• The trial was repeated three times

Laboratory Findings

Independent laboratory reports recorded:

• Listeria spp: 0 cfu/plate (Not Detected)

Listeria 2

• Air curtain grille swab: Not Detected

Listeria 1

Across three monitored trials, no Listeria was detected during the testing period.

Important Clarification

Air curtains are not antimicrobial devices.
They do not kill bacteria.
They are not a substitute for hygiene protocols.

But what they do provide is climate separation.

By reducing uncontrolled warm, humid air entering the space, they support:

• More stable temperatures
• Reduced condensation
• Lower humidity spikes
• Less compressor stress
• More consistent internal conditions

And stable environments are easier to control, monitor and manage.

The Commercial Perspective: Risk Management Through Control

Food safety incidents are rarely caused by a single failure.
They happen when multiple small instabilities stack up.

• Temperature fluctuation.
• Condensation.
• Air movement.
• Traffic patterns.

Each one adds risk.

Climate control doesn’t replace hygiene management, it strengthens it.

For airline catering and cold chain operators, that’s not a theoretical benefit. It’s operational insurance.

The Broader Implication

This trial did not prove that air curtains prevent Listeria.

What it did demonstrate was:

• No contamination introduced during operation
• No detection recorded during the monitored period
• Controlled, stable environmental conditions during testing

In high-compliance food environments, reassurance backed by independent lab testing carries weight.

Air curtains should be viewed for what they are:

• A temperature stability solution.
• A condensation reduction tool.
• An energy efficiency measure.
• A climate control barrier.

And in environments where a single contamination event can cost millions, supporting environmental control is never a small thing.