The consumption of tinned meats must always be associated with certain risks. The assurance that proper supervision is exercised in the choice of the meat, that it is canned under sanitary conditions, and preserved by scientific methods, is not in itself sufficient. Even with this much guaranteed, there will always be a possibility of accident or oversight in the process of canning. It is, therefore, just as well that the consumer should know how to safeguard herself.
The putrefaction which it is desired to render impossible in the preservation of meat in tins is due solely to microbes. These microbes constitute nature's method of getting rid of dead vegetable and animal matter, and, ipso facto, may produce a poisonous substance, ptomaines, the source of the much dreaded and frequently fatal ptomaine poisoning.
Danger, again, may arise through the contents of the tin absorbing some metal or solder, and so causing metallic poisoning. The Canning Process
In the process of canning the tin is first filled with the intended preparation and the top, which contains a small hole, is soldered on to the body. The tin is then immersed in boiling water to drive out the air and kill any microbes which may be present. Then the small hole in the top is soldered up. Provided that complete sterilisaton and exclusion of air from the tin has been effected, the contents will keep good for years, and can be eaten with safety. It is important, however, to see that the tin has not been punctured.
If the preparation be insufficiently sterilised, or if any air be present in the tin, the microbes will probably produce putrefaction, and a gas will be evolved from the meat. The pressure of this gas inside the tin will cause the top and bottom to bulge. A tin in this condition is known as " blown," and carries its own condemnation in its bulging ends. This bulging is accepted by food inspectors as sufficient reason for condemning the contents as unfit for human consumption. It is wise, therefore, to make a point of rejecting any tin which exhibits this characteristic however slightly.
Should further proof be thought necessary, the tin may be immersed in water, and the end punctured with some sharp instrument in order to discover if a gas will issue from the hole. The very fact of any gas emerging is positive proof that the meat is unsound.
Unscrupulous dealers, however, sometimes puncture the tins themselves, and having re-heated them, solder up the second hole and pass the tin off as sound.
This, if skilfully done, is not easy to detect. In the ordinary course of events, therefore, we have to rely upon the vigilance of our food inspectors to confiscate the tins before they reach the process of renovation.
The subject of ptomaines is very imperfectly understood by scientists. In some cases the ill effects that have resulted from the consumption of tinned meat have been attributed to toxic substances other than ptomaines; in other cases the effects have been held to be due to the action on the human system of the microbes still alive in the meat. The truth is that, if these poisonous substances be present in the food the microbes that produced them may have been killed by heating without the poisonous principles being rendered harmless.
In purchasing a tin of preserved meat, therefore, attention first should be directed to the possible presence of more than one spot of solder, and secondly to the ends of the tin to ascertain if they are " blown."
The contents of the tin always should be sweet. Even a slightly unpleasant odour or a "soapy " taste will warrant its rejection. If, when opened in the dark, the contents exhibit any phosphorescence, the tin should be condemned. A metallic flavour indicates the presence of metallic impurity.
The contents should not be allowed to remain in the tin after it has been opened, and should be consumed as soon as possible.
Glass versus Tin
A great many firms pack their wares in glass vessels in lieu of tins, and this form of packing, if properly carried out, is held by many to be preferable, as in glass vessels there is no risk of metallic poisoning. Against this, however, is the fact that complete sterilisation in glass is more difficult to secure, and it is questionable whether tinned meats may not be taken to be more wholesome, generally speaking, than meats packed in glass. Flaws in the latter, however, are more readily accessible to the public eye; and on this account meats packed in glass frequently find more favour with the ordinary housewife than meats packed in tins.
It must be remembered that there is now a regular trade in re-packing food - that is, meat, fish, or fruit which has been imported in tins is put up in glass directly it reaches England, in order to catch the eye of the careful housekeeper who does not fancy tinned goods. Legislation on the subject of such transactions has been talked of, and it is to be hoped that this matter will soon be looked into by the authorities.
The following are good firms for supplying foods, etc., mentioned in this Section: Messrs. G. Borwick & Sons, Ltd. (Baking Powder); Brown & Poison (Cornflour); J. S. Fry * Sons, Ltd. (Cocoa); Samuel Hanson & Son (Red, White & Blue Coffee); C R. Shippair. (Tongues, Potted Meats, etc.)