FEATURE
INCORPORATING COLD CHAIN
Double-faced corrugated board is the predominant form used for produce containers . It is produced by sandwiching a layer of corrugated board between an inner and outer liner of paper-board . The inner and outer liner may be identical , or the outer layer may be pre-printed or coated to better accept printing . The inner layer may also be given a special coating to assist in moisture resistance . Heavy-duty shipping containers , such as corrugated bulk bins that are required to have high stacking strength , may have double- or even triple-wall construction .
Corrugated board manufacturers can print certificates on the bottom of containers to certify certain strength characteristics and limitations . Both cold temperatures and high humidities reduce the strength of this packaging . Unless the container is specially treated , moisture absorbed from the surrounding air and their contents can reduce the strength of the container by as much as 75 percent . Anti-moisture coatings are available to substantially reduce the effects of moisture .
Waxed cartons may be required for certain products and destinations but are generally used for produce items that must be either hydrocooled or iced . The main objection to wax cartons is disposal after use — wax cartons cannot be recycled as per standard cartons .
In many applications for corrugated containers , the stacking strength of the container may be a minor consideration . For example , canned goods carry the majority of their own weight when stacked . Fresh produce usually cannot carry much of the vertical load without some damage .
Cartons of citrus , ready to be sent to the harbour for the export market .
Therefore , one of the primarily desired characteristics of corrugated containers is stacking strength to protect the produce from “ crushing or bruising ”. Most of the stacking strength of corrugated containers is carried by the corners . For this reason , hand holes and ventilation slots should never be positioned near the corners of produce containers .
Interlocking the packages ( cross stacking ) is universally practiced to stabilise pallets . Cross stacking places the corner of one produce package at the middle of the one below it , thus reducing its stacking strength . To reduce the possibility of collapse , the first several layers of each pallet should be column stacked ( one package directly above the other ). The upper layers of packages may be cross stacked as usual with very little loss of pallet stability .
In South Africa , there are numerous styles of corrugated containers or carton boxes as commonly referred to . Research has shown that there are in excess of 20 manufacturers in this packaging type alone . This is not surprising given the fact the exports cumulatively from this country exceed 900 million boxes of produce annually . The box carton locally has received quite a lot of attention of late owing to the fact that there are so many manufacturers and each wants to implement their own design . More around this can be viewed in prior issues of Cold Link Africa .
Almost all corrugated containers are shipped to the packers flat and assembled at the packing house . To conserve space , assembly is usually performed just before use . Assembly may be by hand , machine , or a combination of both . Ease of assembly should be carefully investigated when considering a particular style of carton .
For many years , labels were printed on heavy paper and glued or stapled to the produce package . The high cost of materials and labour has all but eliminated this practice . The ability to print the brand , size , and grade information directly on the container is one of the greatest benefits of corrugated board containers today . There are basically two methods used to print corrugated board containers : post printed - when the liner is printed after the corrugated container has been formed , and the process is known as post-printing . Post printing is the most widely used printing method for corrugated containers because it is economical and may be used for small press runs . However , postprinting produces graphics with less detail and is usually limited .
Pre-printed high quality , full-colour graphics may be obtained by pre-printing the linerboard before it is attached to the corrugated paperboard . Whereas the cost more , the eye catching quality of the graphics makes it very useful for many situations . The visual quality of the package influences the perception of the product because the buyer ' s first impression is of the outside of
28 www . coldlinkafrica . co . za COLD LINK AFRICA • September 2022