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CANNED GOODS

Description: Generally speaking, canned goods, provided they have been properly treated and properly canned, will keep indefinitely, but there are various factors which will give rise to rapid deterioration of the product. For example, the acids of certain fruits and vegetables may give rise to pin holes in the metal containers. Any imperfection in the product will cause rapid deterioration. Pin holes may also be caused by rusting, and the rust in its turn may have been caused by other means than contact with fresh or salt water. In some instances, examination of rusted cans has demonstrated that the glue used to label the cans contained or subsequently absorbed a certain quantity of moisture which had caused the cans to become rusted and subsequently holed. Rusting and subsequent holing may also be due to sawdust from wet or unseasoned timber being used in the packing, or even to wet or unseasoned timber being used in the making of the cases. Blowing of tins is generally ascribed to improper closure of the tins or incomplete sterilization of the contents, but wetting or denting of the tins during transit may cause minute holes through which bacteria can gain access to the contents. Rusted or strained seams are a similar cause; improper or insufficient packing can account for a variety of damage in canned goods. Cans of sub standard quality and insufficient tightness of the seams are a further cause of blowing, as is insufficient thermal processing, and the surveyor should be careful to note in his report any such deficiency. Blowing of tins may cause rusting and staining of otherwise sound tins, and, where this has occurred, the surveyor should make particular mention of this fact in his report. Discoloration of goods in cans may be the result of the action of sulphur on the container, and certain types of goods should be packed in glass or enamel containers. If the air has not been completely extracted from the cans, or the cans have not been properly sealed or the contents not properly sterilized, deterioration may occur, which will be accelerated in high temperatures. Defects in tins may be obscured by labels, these defects being of such a nature as to allow the entry of bacteria or seepage of contents. Where rusting of cans has not given rise to leakage or blowing, it may be possible to remove the rust spots, treat the surface of the tins with a suitable oil and so restore their appearance. Similarly, if canned goods have been submerged in water they should be washed thoroughly in fresh water and dried immediately on exposure to the air, then coated with a suitable oil or grease to prevent rusting. If certain canned goods are subjected to unduly low temperatures, this may result in the crumbling of the contents of cans, the bursting of the seams and sweating and rusting. Provided the cans have not burst, nor the seams loosened, they should be allowed to remain in that condition until such time as they are ready for use, when they should be allowed slowly to assume the natural temperature. Claims arise on account of sweat damage when shipment takes place in the spring from ports of British Columbia to Canadian East Coast ports, via Panama, due to the fluctuation of temperatures during the voyage. When loaded at Vancouver, or other ports where the temperatures are low, the goods are subjected to increased temperatures during the passage through the Canal, causing condensation when the vessel once again enters the lower temperatures of the Gulf of St. Lawrence. As these vessels usually carry shipments of lumber, the risk of sweat damage is increased. An investigation carried out on the West Coast of North America disclosed that heaviest sweat damage can be traced to Canneries not equipped with pre-cooling warehouses. Shipments which left the Canneries without pre-cooling and traveled by trucks through cold nights on their way to the harbor were found to contain cans with moisture spots under the labels, and along the rims or tops of the cans. Unsuitable or insufficient packing can account for a variety of damage in canned goods. "Lip-lifting" may be caused by the upper and lower edges of cans working against one another during transit. Crushing or denting reduces the cubic capacity of the tin and distends the ends, giving the appearance of blowing. Care should be taken to identify this class of damage. Denting or springing giving the appearance of blowing may be due to the manner in which they have been pneumatically closed, or due to the cans being overfilled. Generally speaking, where a can is not leaking or the seams are not seriously damaged, the contents may be edible. Tins packed in boxes can become defective through production faults. Defective tins with these faults can be divided into two groups - "Hollow sounders" and "Leakers." Hollow sounders can be identified by tapping them at both ends, and leakers can be recognized by swelling.
Index: 141
Commodity Name: CANNED GOODS

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