Refrigerated transport, handling and distribution

The cold chain principle of food handling and distribution is that the product will be maintained at suitable conditions all the way to the point of sale. This requires transport and various kinds of storage. 

The transport of cooled produce, using mechanical refrigeration, was one of the first major uses, dating back to 1880 and only 20 years after the first static cold storage. The present annual movement of refrigerated produce exceeds 50 million tonnes. 

Direct injection of liquid nitrogen is also used on the larger vehicles. This is carried in metal vacuum flasks and the vehicle will he reliant on depots where the liquid nitrogen flask can he refilled. The only mechanical equipment will he a thermostatically controlled solenoid injection valve. 

Vehicles for local delivery journeys tend to he in use only in the daytime and spend the night static. Cooling systems can run from a mains electricity supply providing they can hold a sufficiently low temperature while on the road. Use is made of eutectic plates (see Section 7.5) and of cooling the vehicle hody only when in the garage, relying on the cold mass of produce and good insulation to 

Rail traffic is mainly in purpose-built, insulated wagons, many of these having self-contained refrigeration systems. Some produce is pre-cooled and/or iced. Re-icing stations are available on the longer routes in Europe. 

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