Cold chain

A cold chain is the set of cold stores, refrigerated vehicles and checks that keeps food or medicine within a set temperature range at every step, from where it is made or grown to where it is used. It is called a chain because it is only as good as its weakest link. If a box of vaccines warms up for a few hours on one loading dock, the vaccines may be useless, even if every other step was cold.

Here is how it works in general. Each product has its own temperature range. Most vaccines and insulin must stay between 2 and 8 degrees Celsius. Frozen food is kept at about minus 18 degrees. Fresh milk and chilled meat are kept between 0 and 4 degrees. Each leg of the trip has its own cold equipment: a cold room at the farm or factory, a refrigerated truck, a cold store in the city, a refrigerator at the shop or pharmacy, and an insulated box for the last delivery. On each leg, a temperature logger, a small device, records the temperature every few minutes. Many loggers send their readings over the mobile network, so that someone can act as soon as a reading goes out of range. When the goods change hands, the receiver checks the record. If the temperature went outside the range, the goods may have to be tested or thrown away.

The cold chain matters a great deal in India. A large share of fruit, vegetables and fish spoils between the farm and the buyer, partly because there are too few cold stores and refrigerated trucks. India's vaccination programme runs one of the largest public cold chains anywhere, with tens of thousands of cold points.

Take, for example, a milk and grocery subscription. The milk is chilled at the dairy, carried in refrigerated vans at night, and left at the door before dawn, before it has time to warm up.

Consider a truck carrying frozen fish from a harbour to a city. Its refrigeration unit and loggers report the temperature through cold-chain monitoring, and the transport company receives an alert if the load starts to warm.

For instance, many biologic medicines are large proteins that are damaged by heat. Cold-chain logistics companies keep them in refrigerated warehouses and vehicles all the way to the pharmacy shelf.

How is a cold chain different from telematics? Telematics is the data that a vehicle sends about where it is and how it is being driven. A cold chain is the whole system of cold storage, cold transport and checks. Telematics is one of the tools that monitors a cold chain, on the legs where the goods are on a vehicle.