This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
Canned, or tinned fruits, suffer if allowed to remain at all in the tin after it has been opened; their acids act on the metal, and poisonous products are formed. The canned fruits have always been already cooked, for a time varying from five minutes even to some hours, so that but little further cooking is needed. To retain the natural flavour of Tomatoes (tinned) they should be parboiled quickly over a hot fire; if they are allowed to simmer long a bitter flavour becomes extracted from the seeds, and is imparted to the fruit. Asparagus is best cooked in the can before it is opened, by immersing this into boiling water for from twenty to thirty minutes; then open the can, and slide the contents carefully into a dish, taking care not to break the tender tips. With regard to tinned Lobsters, and Shrimps, owing to the large quantity of sulphur which they contain, there is a great likelihood of their turning black if their flesh comes in contact with the tin when they are packed dry; for which reason they should have been first put into parchment, or linen bags, or preserved in wood-lined cans.
A story is told of an American officer, a man of good physique, who throughout several years of exacting service at an out-of-the-way western post subsisted entirely on "canned" goods. "It was his custom to pick up, and open a can at haphazard, one at each meal; whether the contents were fish, fowl, vegetable, meat, or fruit, he ate that, and nothing more, and he still lives to tell the tale. But he was actively engaged all the time, both physically, and mentally, except when asleep; and he breathed fresh air in the open for the twenty-four hours of every day, and night." In New York, U.S., hundreds of millions of canned foods are consumed annually, but there has never been an authenticated case of poisoning by any one of the cans that could not be traced, and attributed to the carelessness of the consumer. At the present day no solder is used inside a tin, but the can is strictly a tin envelope with the contents in vacuo, as shown by the ends of each can being sucked inwards; if these ends are springy, or bulge outwards, then the vacuum does not exist, and the contents, being spoilt, must be thrown away.
The Epicure (December, 1903) tells a true story of an old lady who had a pious horror of tinned foods. "Once she supped at a friend's house, partaking of an entree which specially commended itself to her taste, insomuch that she resolved to ask for its recipe. But a fortnight elapsed before she could see her friend, and urge the request; then an explanation ensued; - the admired dainty was a tinned abomination! Incontinently the old lady went home, and took to her bed with a severe gastric attack, which shattered her strength, and more than ever confirmed her prejudices." Not improbably other such instances occur, where the imagination has more to answer for in illness from canned produce than the comestible itself.