Application of heat, after the filling and sealing of the can, is relied on for complete destruction of all micro-organisms. Occasionally, organisms enter the can after heat processing, or bacteria spores survive the heating process, and spoilage may occur. Where organisms gain entrance after processing, gas production will normally cause swelling or doming of a can. Almost any bacterium or fungus may be the cause. Doming of cans due to microbial growth should not be confused with physical distortion of the can due to mechanical damage.

If, due to a manufacturing defect, spore-forming bacteria such as Clostridium spp. and Bacillus spp. survive the heating process, they may grow and cause putrefaction, fermentation or rancidity. Many of these bacteria are adapted to high temperatures and develop only where the storage temperature is high. Some do not produce gas; accordingly the can does not become swollen.

Damaged cans should be destroyed because of the risk of contamination with Clostridium botulinum, which produces a heat-stable botulinum toxin that is potentially fatal. Samples should be sent for examination in all instances where claims or retort actions are contemplated against the donor, shipper or manufacturer as a result of poor or defective quality of cans.

Leaking

Blown

Leaking

Leaking

Blown

Container transport

• The type of container selected depends on the season, the route, the duration of the voyage and the container stowage space. Canned foods are generally transported in standard containers, subject to compliance with the water content of flooring and packaging.
• To prevent damage to the cargo, the container must always be absolutely dry and water-tight.

• It is also imperative that the goods be protected from moisture (rain, snow) during cargo handling and from excessively low and high temperatures, as the packaging (paperboard cartons) is extremely sensitive to moisture and loses stability. There is an additional risk that cans may lose their labels or cans may corrode.
• Both the cartons and the cans are relatively sensitive to mechanical stresses. If the packages are handled improperly, e.g. thrown, there is a risk of damage (e.g. cartons may become battered). The cargo should accordingly be handled with appropriate care.

• In port, care should be taken to ensure that the containers do not stand out in the open and that the duration of storage is as short as possible.
• The cargo must not be stowed near heat sources (risk of blowing caused by heat).

• Because of its considerable impact- and pressure-sensitivity, packages of this cargo must be secured in such a way that they are prevented from damaging each other.
• Spaces between packages or pallets must be filled, to prevent slippage or tipping. By selecting the correct packaging size or cargo unit (area module or area module multiple), holds can be tightly loaded (without spaces).

Temperature

Preserved foods require particular temperature, humidity/moisture and possibly ventilation conditions

• At temperatures < -2°C there is a risk that cans may blow due to freezing of their contents (ice expansion).
• At temperatures > 20°C, cans may blow due to heating which results in thermal expansion.

Long-term exposure to high temperatures may lead to:

• separation, settling
• marbled effect in preserved foods which have a high protein content (meat, fish, peas, beans) due to sulfidic corrosion. This occurs if the sulfur components of the proteins act on tin or sheet iron
• Where container transport is used, the risk of blowing due to the action of heat and frost is greatest in the vicinity of the container roof. The additional moisture released as a result of leakage due to blowing aggravates wettening of cartons and corrosion of cans.

• Canned foods require particular temperature, humidity/moisture and possibly ventilation conditions
• The cartons must be protected from all forms of moisture (seawater, rain and condensation water) and from excessive humidity levels. Typical patterns of moisture damage to a cargo of preserved foods are as follows:
• loose, mildewed, unattractive labels
• mold on and in cartons
• crushed cartons, due to moisture penetration, leakage, total loss
• corroded, discolored cans; corroded cans are unsalable
• If the glue used to stick on the labels is not acid-resistant, corrosion is encouraged even at normal humidity levels. High-grade, water-resistant adhesives must be used for labels.
• Corrosion damage arising during overseas shipment of cans in containers

Where preserved foods are transported in containers, the causes of condensation are as follows:

• Excessive water content in cartons, pallets and wooden dunnage 
• Temperature gradients within the cargo stack, leading to cargo condensation
• Drop in temperature in the peripheral zones of the container, in particular at the container roof, leading to container condensation
• Part-loads with different temperatures, e.g. simultaneous stowing of relatively cold food cans and relatively warm hygroscopic goods.
• Containers should not be packed during precipitation. It is essential not to stow any wet or snow-covered cargo units in the containers.
• The wooden flooring of the containers must be absolutely dry. The water content of the flooring should be 12%.
• To protect the cargo from condensation water dripping down from the container roof, it may be helpful to use anti-condensation films or a packing paper lining, or silica gel bags (as recommended by WFP).

• Preserved foods require particular temperature, humidity/moisture and possibly ventilation conditions
• If the product is at "shipping dryness", i.e. the water content of the paperboard cartons is 5 - 8%, ventilation is not normally required.

• Canned foods are products in which biochemical and microbial processes have stopped and which are isolated from the external environment, as they are in hermetically sealed packaging (cans).

No risk.

No risk.

• Active behavior: Canned foods do not cause odor-tainting, as they are enclosed in hermetically sealed packaging.
• Passive behavior: Canned foods should not be stowed in a hold/container/Wh together with odor-tainting goods.

Contamination

• Active behavior: Canned foods do not normally cause contamination. However, other goods may be contaminated by leakage caused by breakages.
• Passive behavior: Canned foods should not be stowed in a hold/container together with goods which cause contamination or produce large amounts of dust.

• Canneed foods must not be stowed/stored in a hold/container/warehouse together with toxic goods (foodstuffs legislation).
• If optimum storage conditions are not complied with for a relatively long period, depreciation occurs with respect to the can contents, which may sometimes present a serious hazard to health. One characteristic feature of reduced quality is "blowing", in which disadvantageous changes generate gases ("blowing gases"), which cause the bottom and lids of cans to swell and even burst. Swelling caused by blowing differs from straightforward bulges in that it either cannot be pressed back in at all or bulges out again when pressure is released.
• Apart from apparent blowing (thermal causation, expansion due to freezing/heating), blowing may also have microbiological and chemical causes. In the case of microbiological blowing, the typical blowing gases are, for example, hydrogen sulfide (where protein is present), carbon dioxide and hydrogen. Chemical blowing may be observed in the case of preserved fruits and jams, hydrogen being produced due to the reaction of metal and acids and corroding the insides of the cans.

In all cases, blown, damaged cans must be destroyed.

• No risk.

Mechanical influences

• Cartons should not be thrown during handling, as there is a risk of their becoming battered. Mechanical stresses during cargo handling may, for example, destroy the adhesive strips or dent the carton walls and edges.
• Cartons which have inadequate strength are frequently damaged when stowed carelessly and inappropriately. The cans become dented and squashed. Leakage results in total loss. If the contents of the cans leaks out, the cartons become soft and the carton stacks may collapse. Large cans should be packed in compartmentalized cartons.
• The packages must be secured appropriately in the container or truck so that they cannot move during transport. In the case of container transport, it is also important for the goods to be secured in the door area so that they cannot fall out of the container when the doors are opened.

• Loss of volume may be caused by breakage, leakage or theft. To avert the risk of theft, in the case of container transport the containers should be stowed such that the doors of adjacent containers block each other, thereby preventing access to the container interior.
• Warehouses must be locked.