Reefer

Reefer is the shipping term for refrigerated transport, covering both purpose-built refrigerated ships and, increasingly, refrigerated shipping containers. Its role is to carry temperature-sensitive cargo, bananas, citrus and other fruit, vegetables, meat, seafood, dairy, flowers and pharmaceuticals — across the world without spoilage, by holding the cargo at a set temperature throughout the voyage. This cold chain is what allows fresh produce to be grown in one hemisphere and eaten in another out of season, and it is a large and specialised part of world trade.

Historically this trade was carried by dedicated reefer ships, insulated vessels with refrigerated holds and their own cooling plant, often painted white to reduce heat gain and built for speed to move perishables quickly. While specialised reefer ships still operate, much of the trade has shifted to refrigerated containers, known as reefer containers or integral reefers, each with its own refrigeration unit that plugs into power supplies on the ship, at the terminal and on the truck or train. Container ships provide numerous reefer plug points, and stowage planners must ensure powered slots and monitoring for every reefer box.

Carrying reefer cargo demands careful control and monitoring. The correct carriage temperature varies by commodity, and some cargoes need controlled or modified atmosphere (adjusting oxygen and carbon dioxide levels) to slow ripening and extend shelf life. Ventilation, humidity and airflow all matter, and temperatures are recorded continuously so any deviation can be investigated, since a failure can ruin a high-value cargo and lead to claims. Pre-cooling the cargo before loading, checking the unit's operation, and maintaining the cold chain at every transfer are essential. Reefer transport is therefore one of the more technically demanding and commercially valuable segments of shipping.