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Are our food products in shipping containers safe from fungi and mold spores..??

Within the food supply chain industry, there seems to be a general lack of knowledge about container stowage and environmental conditions aboard a ship.. If you ask anyone in food export and imports about how and where their cargo is stowed, you will likely get a blank stare in many parts, even though there are many reasons why the stowage of these products matters..

The topic here is one such, with implications for the safe carriage of food products including the potential spread of non-native organisms such as fungi and mold spores especially in containers stowed under-deck on cellular ships..

Are spores of fungi and mold being shared on ships by and between containerized food cargoes, both ambient and refrigerated..??

This is a new burning question in 2023 as per industry veteran Andy Connell..

In this article, he examines whether there is a real elephant in the room or if the risk is so low that it does not deserve consideration..??

To date, no entity has investigated the possibility of spores of fungi and mold being shared on ships or quantified the possible risk, or de-bunk it. We have learned that spores do not respect closed doors. Science teaches us this.

In the food export supply chain, we place a high degree of diligence on the sanitization of

  • The production area
  • The harvest process
  • The transport to the packing warehouse
  • The packing facilities
  • The reefer containers that need to pass stringent sanitary tests before its release for shipment to the exporter

Cleanliness of containers carrying cargoes of all types to avoid the spread of pests and invasive species is also a focus for the UN’s Foad And Agriculture (FAO) International Plant Protection Convention (IPPC) with its Sea Container Task Force (SCTF) and the North American Sea Container Initiative (NASCI), plus industry initiatives including the Cargo Integrity Group, made up of 7 industry associations and organizations representing different stakeholders in the container supply chain. (See ISPM #25)

But what about INSIDE the ship itself?

When stowed above deck over the hatch cover on a ship, the surrounding free air in the environment is moved constantly so any spores are carried off and the risk of infiltrating a container and infecting the product is very low.

However, containers stowed below decks under the hatch cover are sealed in a ‘watertight’ compartment. Although fans exchange the air from time to time, this is not a 24/7 activity, but cyclic.

The containers can spend many hours in a closed space for safety reasons (watertight compartment) and all bay fans cannot run simultaneously from one auxiliary generator. The ship must stay afloat after all.

However, this compartment is not sanitised for pathogens before, during or after discharge or loading of equipment. Fungal and mould spores will not be detected, because no one is looking for them. If the food product category or variety calls for an air exchange during transport, as most do, then an air exchange vent on the container allows free airflow in and out of a control valve.

This vent may be set at 15m³ or even 25m³ per hour air exchange and is colloquially known as ‘the vent setting’.

In dry van boxes carrying ambient food cargoes like nuts, onions and potatoes, the vents are always open, regardless.

If there are other products also in containers with open vents, then the logic is simple to follow: any spores exhaled from one container may be ingested by neighbouring containers in the same compartment (bay).

Just as one person with a common cold may infect others in a closed room, so too can just one container with spores infect all others in the same space. It’s called cross-contamination. Or cross-infection.

A familiarisation of the bay layout of a cellular ship will soon identify which bays are isolated in terms of compartmentalisation and which are shared. This will differ across the class and the size of a ship.

The ships allocated to the South African trade by carriers offering refrigerated container services are generally in the post-Panamax category, between 4,000 and 6,000 TEU. See category C in the below image

fungi and mould spore contamination container shipments

Side note: ship container capacity is measured in the currency of TEU – Twenty Foot Equivalent Units. If said ship is of 6,000 TEU capacity, it means it can carry 6,000 x 20′ containers or 3,000 x 40′ containers or any mix of the two in between.

Anatomy of a cellular ship

Cellular Ships which are constructed to carry only container equipment, are divided into bays, numbered from front to back (stem to stern). There are 6 principal different types of containers (referred to in ship-speak as ‘equipment’).

The bays below the hatch have fixed steel vertical rails to guide the containers down to the bottom of the hatch (onto the tank tops). This makes the ship, seen from above, resemble a beehive with the many cells for hosting containers, hence the name ‘cellular ship’.

Odd-numbered bays are for 6m (20ft) long containers and even-numbered bays are for double 6m or single 12m (40ft) equipment.

There can be up to 220 containers in one compartment (two consecutive bays) under deck on a ship. Figure 2 shows a typical cellular ship anatomy. The ship is segmented into many bays. Often two consecutive bays share the same airspace as they form one watertight compartment. Containers are stowed according to port rotation and not by category or number except in case of regulated cargoes such as dangerous goods.

fungi and mould spore contamination container stowage fungi and mould spore contamination container stowage fungi and mould spore contamination container stowage







The container stow space underdeck may have containers with a spectrum of food cargo, including different types of perishable products (flowers, vegetables, fruit, nuts), and many categories of fresh produce (citrus among containers with avocados, macadamias, blueberries, Sharon fruit, etc.).

Each type and category, as well as different destinations, must comply with similar or different phytosanitary regulations. Some are sterner than others. There will also be many containers with random types of food cargo in dry van equipment, which is most often open-vented.

This means that if one product has stringent sanitation processes such as cold treatment sterilisation to exclude quarantine pests, an adjacent container may not have a product with such strict compliance requirements and may not even be in reefer equipment. Nuts, potatoes, and onions, for instance, are usually shipped in general-purpose containers, not refrigerated containers.

So, there is every reason for concern that among the containers stowed below deck, there may well be containers carrying spores of fungus or mold. This is a risk to any containers which have their air exchange vents open.

The underdeck compartment is, therefore, an ideal petri dish for growing culture and cross-infecting cargoes in containers with open-air exchange vents.

Go figure – if I can cough on you in an elevator and you catch a cold from me, so too could one container get infected by another within the same bay. This issue has now started to catch the attention of experts in food research and technical services, shipping, and logistics, as well as technology innovators. So, watch this space.

About the Author :

Andy Connell is a veteran in the logistics industry specialising in the shipment of perishable goods like fruits, vegetables, and flowers and also a part-time lecturer about the industry sharing his knowledge at various industry educational institutions.. 

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