30 THE CANNING OF FOODS. 



There are two conditions, known to the trade as " springers " and 

 " flippers." A springer is a can the end of which will bulge slightly 

 after a time, but on opening there is found neither gas nor spoilage, 

 though the cans have the appearance of being swells. This condition 

 has been found to be due to overfilling or to packing cold. Such 

 goods when placed in a warm grocery will bulge, due to the tempera- 

 ture. A flipper is a springer of such mild character that the head 

 may be drawn in by striking the can on a hard object. It is always 

 possible to tell a swell from a springer by the use of a microscope, as 

 in the former there will be large numbers of organisms while in the 

 latter there will be very few. 



While a spoiled can of food should never be eaten, tho danger of 

 poisoning from fruits and most vegetables is very remote. Ptomains 

 or other poisons may form in meat, milk, and fish, but rarely, if ever, 

 in vegetables. 



EFFECT OF HEAT AND COLD. 



Canned foods may be injured by an excess of either heat or cold. 

 Some products are injured more than others. The effect of pro- 

 longed heating is to cook the contents to a pulp. This is seen at 

 times, in the case of peas and tomatoes in particular, when the cans 

 have been stacked tightly before being fully cooled. The liquor will 

 become cloudy from short heating, thick and heavy from prolonged 

 heating, and the peas softened and broken if it is continued for a 

 number of days. The writer has seen peas stacked that were warm 

 for three weeks after packing. Tomatoes become soft and pulpy, 

 and often turn a walnut brown if stacked hot and the heat is retained. 

 All fruits become murky and lose their distinctive flavor and odor. 

 Canned foods will stand the high temperature of summer very well, 

 but as far as possible they should not be placed in the hot sun nor 

 kept in a very hot storeroom. The effect of moderate heat is not 

 nearly so marked as might be expected. 



Cold seems to have no ill effects upon canned goods unless it goes 

 below the freezing point. Most canned foods will stand a little 

 freezing without appreciable change. Kepeated freezing and thaw- 

 ing cause the goods to become flabby and give a flat taste. In all 

 cases the interior of the cans shows a distinct attack upon the tin. 

 With fruits, the coating of the cans is made to appear as though 

 it were galvanized. Canned foods will resist a fair degree of heat 

 or cold without serious injury, but continued heat or a very high 

 temperature, or repeated freezing and thawing will cause deteriora- 

 tion in quality. 



Foods properly prepared and kept under reasonably good condi- 

 tions deteriorate very slowly, so that cans carried from one year to 

 another may be as good as, or better than, the latest pack, depending 



