SCIENCE AND INDUSTRY. 
Leaks in Fruit Containers. 
R. GREIG-SMITH, D.Sc. 
“The Tin Factory, in what might be termed its trial run, was an expensive 
experiment. In a total of 107,191 23-lb. cans made by this Factory, and used in 
canning, 15,408 were found during processing to be leaky, and of those manu- 
factured and purchased 5,013 developed leaks in the warehouse. Besides these, 
6,959 were spoiled in manufacture, and 4,773 faulty cans were found amongst 
those purchased, These make a total loss of 14.7 per cent. of the 24-lb. cans 
used. Further, of 3,140 No. 10 cans purchased, there was a loss of 23 per 
cent. through leaks. It is still a controversial point as to where the fault 
lies, but in the light of cold fact, wherever the fault, considerable monetary 
loss has been the result.” 
—State Industrial Undertakings (New South Wales) Report of the Auditor- 
General, 1918, p. 77. 
The quotation is interesting in showing the heavy loss that may occur in a can- 
nery, even with the most improved plant, for that at Leeton, on the Murrumbidgee 
Irrigation Area, is of the most modern type. It may be that much of the loss was 
caused by the faulty closing of the containers, for that is the weak point about 
the preservation of fruit and vegetables. Unless solder is used, no machine can 
fit on a lid and make the container absolutely air and water tight, that is, 
make it equivalent to a hermetically-sealed vessel. ‘There is always a weakness 
where metal joins metal with a non-metallic luting material at the points of 
contact. ‘The internal pressure developed during the processing finds out the weak 
places, and there is leakage, with its attendant troubles. 
My attention was called to the irregularities in the canning process by one of 
our leading fruit-canners, who desired to know the reason for the “ springing ”” 
of his tins of preserved fruit. Some time after processing, the tins, which nor- 
mally should haye concave ends, indicating a partial vacuum within, become 
bulged at one or both ends, 
clearly showing that internal fermentation has 
occurred. Such containers are condemned as containing food unfit for human 
consumption, as doubtless they do. Putting them through the boiler again, that 
is “reprocessing ” them, does not do much good, as they may become worse, and 
the reason for this becomes evident when the cause of the “springing ” is under- 
stood. 
Tn processing pears, for example, the fruit is pared, halved, cored, washed, and 
filled into the empty containers, which are placed upon a travelling belt. A girl 
fills them with boiling syrup up to anything from half to a quarter of an inch 
from the top. Then they pass to the closing machine, which turns the lid on 
the cylindrical wall of the container by forming a double interlocking hook. The 
tin goes to the boiler, where it is cooked, On emergence from the boiler, the 
tins are stacked on the floor of the cannery until they are sufficiently cold to 
enable them to be taken to the storage room, where they are arranged in tiers. 
After a time many of them begin to ooze syrup from the junction around the top 
or bottom, and the leakage may continue, or it may stop, and the syrup hardens, 
forming a lute of dried syrup. It is among these that the springers are 
afterwards found. . 
The “springing” results from th 
e production of gas inside the tin, and, as 
this is unable to escape, the top 
is forced outwards, and the pressure may 
be so great as to cause the syrup to be forced out through the junction 
of the lid with the side of “the tin. The gas must be produced by 
the action of micro-organisms, unless it be by the activity of fruit 
enzymes. The latter is unlikely, partly because of the heat to which the contents 
have been subjected during the cooking process, and partly because, if they 
were the agents, every tin would be a springer. The closed tins are put through 
a boiler, and are in the boiling water for sixteen minutes, which, according to 
laboratory experiments,* is quite enough to thoroughly pasteurize the contents. 
One should, therefore, look to the subsequent treatment for the cause of the 
trouble. We found that the active organisms were yeasts, and as these could not 
have persisted through the cooking process, it follows that they must have gained 
entry afterwards. ‘The most plausible Suggestion is that the lids are not absolutely 
*“The ‘Springing’ of Tins of Preserved Fruit.” 
By W. W. L’Estrange and 
R. Greig-Smith, Proc. Linn. Soc.. New South Wales. i 
1918, p. 409. 
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