Freezing Technology

7.2.1.3 Shipping container

Individual packages must be further packed in a properly engineered container for shipping and storage. Corrugated containers are the most widely used form of containers for shipping frozen foods. Wooden crates and foam polystyrene shipping containers are also used. The use of a corrugated sheet provides exceptional crush resistance. It also has a high capacity for absorbing shock.

         Corrugated fiber board is made of fluted (grooved) sheet glued between two liners. Four types of corrugated board are commercially used and they are A,B,C and E flute. The difference lies in the number of flutes and board thickness. ‘A’ flute -35 flutes per inch and 3/16 inch thickness; ‘B’ flute -50 flutes per inch  and 1/8 inch thickness; ‘C’ flute -41 flutes  per inch and 5/32 thickness; ‘E’ flute -90 flutes per inch and 5/64 inch thickness. Each type has some specifications and advantage over the others.

        Though various coating methods have been used, the most recent technique is called ‘curtain coating’, wherein the coating formulation is applied by a machine designed for that purpose. The continuous film coating acts as an effective barrier, not only against free water, but also against water vapor, gas, grease, oil, and other foreign substances. It is necessary to use a coated shipping container, if there is a possibility of the container being exposed to high humidity or excessive moisture conditions during handling.

        The foam polystyrene container for shipping fresh frozen foods is relatively new. It has the advantage of being water resistant and having excellent insulating properties. After the frozen product is placed inside, the foam lid is applied, and the container sealed off. It has the disadvantage of being somewhat more costly and hardens to handle. The empty containers are bulky to handle and store. However, because of its light weight and insulating properties, the polystyrene container is particularly adaptable to the air transit of frozen foods.