6.5 Post-packaging operations
The introduction of new packaging techniques requires changes to the production routines that do not end when the product is packaged. The packages themselves most often require labelling, coding and collation into larger loads that are suitable for handling and transport to customers. In addition the packaged product should be checked to make sure that it conforms to national legislation or, for export, that it conforms to the legislation of the importing country. Finally the packaged food may require storage until enough is produced to make a full load for transporting to customers.
6.5.1 Collation and preparation of shipping containers
Once packages have been filled, sealed and labelled they are grouped together into larger packs to make handling and transport easier. The most common shipping containers used in developing countries are fibreboard (more commonly known as 'cardboard') boxes which are described in detail in Section 3.1.6. Newer shipping containers include shrinkwrapped and stretchwrapped film around packs contained on cardboard trays (Section 3.2.2). Some products may require the greater protection of wooden crates or boxes and these are described in Section (3.1.5). A summary of the common combinations of package and shipping container is shown in Table 6-2.
In general a filled shipping container should weigh between 10 and 15 kg. If it is heavier it is likely to be dragged rather than carried, if it is lighter it is likely to be thrown rather than carried. Both would result in damage to the package and possibly to the product inside.
Detailed descriptions of metal, wood, shrink/stretch film and fibreboard materials used for shipping containers are given in Chapter 3. In this section the methods used to seal the boxes and drums made from these materials are described.
Wooden boxes, chests and crates are nailed or stapled together, often using metal reinforcement to protect the corners. Fibreboard boxes can be glued, stapled, banded with metal or plastic tape, or tied with rope/twine. Equipment used to seal fibreboard boxes is shown in Figures 3-40 and 3-41.
Drums and barrels
The lids of drums can be pressed into place, held by a retaining band or by a screw thread. Metal drums are found with each of these types of lids whereas it is more common for fibreboard drums to hays banded lids and plastic drums to have screw-threaded lids. Wooden barrels are normally fitted with a removeable wooden plug that is hammered in for transport.
Jute and cotton sacks can be tied with wire or rope, stapled or stitched. An example of an electrical sack stitcher is shown in Figure 3-42. Polythene or polypropylene sacks are usually heat sealed.
6.5.2 Storage and handling of shipping containers
Shipping containers should be stacked in storerooms or on pallets in a neat way so that there is no danger of the stack falling over and that the best use is made of the available space. All packages should be stored off the ground in rows. Space should be allowed for operators to walk between the rows to inspect the food and to collect packages for delivery to retailers or consumers. A typical stacking design for boxes on a pallet is shown in Figure 6-6.
Packaged products are the most valuable materials on site and represent the future income to the business. Every care should therefore be taken to protect them and avoid any deterioration before they are transported to retailers and consumers. Storerooms should be kept as clean as the processing mom and protected against rats, insects, birds and other animals using wire mesh screens and fully sealed doors and ceilings.
A system should be introduced to monitor the amount and types of packaged food that are held in the storeroom. This can be a simple board on which the batches are written as the packages are taken into the store (Figure 6-7). The first packs in are then removed from the store first. This ensures that the processor knows how much food is in the store at any time, the age of the oldest stock and it helps to ensure that stock is used in the correct order.
Although processing and packaging are able to stabilize foods against spoilage it should not be assumed that foods are impervious to climatic conditions during distribution and storage. In general a longer shelf-life for processed foods will be achieved if they are kept in cool dry conditions away from direct sunlight and temperature fluctuations. These conditions are also ideal for maintaining the condition of the packaging materials and the colors used in printing.
The types of deterioration of foods are described in detail in Chapter 2. Processing slows or halts this deterioration provided that the storage conditions and/or package integrity are maintained. If these are not adequate the processed food will spoil in a similar way to the fresh food.
Packaging materials may also deteriorate under incorrect storage conditions. In general most packaging materials will keep their properties and appearance if they are stored in cool, dry and dark conditions. However some types of packaging are more susceptible to deterioration than others.
Glass packs are the most stable and little change in the glass itself is expected under most conditions. However the caps or lids are less stable and in damp, humid and hot conditions metal caps can corrode and the Lining material can separate away (Section 3.1.1.) Metal cans will corrode at weak spots in the tin coating in hot humid conditions (Section 3.1.3).
Plastic caps, jars or bottles are in general fairly stable under most storage conditions, but higher temperatures increase the rate of plasticizer movement into foods from some plastics and soften the plastic which may affect the seal strength. Direct sunlight affects the structure of plastics such as polythene and also makes some printing inks fade more quickly (Sections 3.1.4 and 3.2.2).
Cellulose film has barrier properties that vary with changes in the humidity and temperature of the storage environment which can affect the shelf-life of foods that are stored in this packaging. The barrier properties of other flexible films also change to a small extent with changes in storage temperature but if these changes are not extreme this will not substantially affect the shelflife of the foods being stored (Section 3.2.2).
Papers and fibreboard are very susceptible to changes in the humidity of storage. In high humidity they lose their rigidity and strength thus making puncturing and tearing more likely. In damp conditions the adhesive that is used to form bags, corrugated fibreboard or cartons may also lose its strength and the container will fall apart (Section 3.2.1).
Papers, fibreboard and cloth/fibre containers are all susceptible to mould growth in humid or damp conditions. Even if the mould growth is not visible, it can produce a musty odour which will taint foods that have a delicate flavour or odour.
6.5.3 Transport and distribution
One of the main functions of shipping containers is to protect the food against physical damage and pilfering during transport and distribution. Different containers are designed to have different strengths and these should be matched to the requirements of the food. Table 6-3 shows the effectiveness of different shipping containers in protecting foods against physical damage during transport.
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