409 
THE "SPRINGING" OF TINS OF PRESERVED FRUIT. 
By W. W. L'Estrange and R, Greig-Simith, D.Sc, Macleay 
Bacteriologist to the Society. 
It occasionally happens in the canning of fruit that some of 
the tins, after a time, begin to swell. -Normally, the top and 
bottom of the container are slightlj^ concave, indicating a partial 
vacuum within If, however, one or both is convex, the tin is 
abnormal and is alluded to as a "springer." Such cans are 
rejected, and, as there may be many sprung tins, the loss may be 
considerable to the canner. The cause is generally ascribed to 
leaking containers, but as some fruits are more prone to produce 
" springers " than others, it appeared that much might be gained 
from a study of the phenomenon. It is certainly curious that, 
while pears and some varieties of plums with tight stones are 
frequently aftected in this way, peaches and other stone-fruits 
are but rarely so, even when they are processed or manufactured 
in precisely the same way. Our attention was called to the 
matter, and an examination was made of some of the affected 
tins. 
But before dealing with the results of this examination, it may 
be well to briefly describe the method of processing the fruit. 
The pears, generally the Bartlett variety, are picked, pared, cut 
in two, cored, in some cases sliced, and washed in running water. 
They are then put into empty containers, and placed on a 
travelling belt which carries them past a tap from which boiling 
syrup is run in up to within a quarter or half-an-inch of the top. 
They pass on to a machine which automatically fits on the lids 
and turns the edges. The cold pears reduce the temperature of 
the syrup, which is generally at lbO°F., when the lid is fixed 
and the container made tight. The tins are put into baskets 
and passed through a boiler. The passage occupies 24 minutes, 
and the tins are in the boiling water zone for 16 minutes. On 
30 
410 
THE SPRINGING OF TINS OF PRESERVED FRUIT, 
emerging from the boiler, the ends are bulged, but they become 
concave as the tins cool, while stacked on the floor near the 
boiler. When cold, they are taken to the store, and built up in 
tiers so that any springers may be detected. After a time, they 
are labelled and despatched. 
The springers appear to be of two kinds. One contains syrup 
in an actively fermenting condition: the other is quite still, but 
the syrup has a sharp, slightly acid taste noticeable only to the 
expert taster, and the fruit is apparently quite fit for human 
consumption. The fact that one or both ends of the container 
are bulged is, however, sufficient to cause the condemnation of 
the tin. 
The time during which the fruit is cooked seems to he suffi- 
cient to thoroughly pasteurise the (contents of the tins, but to 
gain some definite information upon the matter, two tests were 
made in the laboratory with fresh pears. These were peeled, 
halved, and cored. 'J'he bulb of a thermometer was inserted in 
the body of one of the halves and the tin was filled up with boil- 
ing syrup, and put into boiling water. The temperatures of the 
pear and of the syrup were read off' at intervals. 
At start 
2 minutes 
5 minutes 
10 minutes 
15 minutes 
20 minutes 
24 minutes 
Temperature in °C. of the 
pear 
syrup 
18° 
27° 
42-5' 
65-5' 
78° 
85° 
89° 
81° 
84° 
87° 
90- 
92° 
94- 
95° 
The conditions were not quite the same as in processing under 
factory-conditions, inasmuch as there was no lid on the con- 
tainer, and it was not completely submerged in the boiling water. 
BY W. VV. L ESTRANGE AND R. GREIG-SMITH. 
411 
For this reason, these temperatures are k)wer than would occur 
in practice, but even as, in the experiment, the pears and the 
syrup were over 70°C. for at least 30 minutes, and over 85* for 
20 minutes, the exposure was quite sufficient to pasteurise the 
contents 
One point about the experiment was, that the tin was put 
into the boiling water immediately the syrup was added; whereas 
in practice, a certain time must elapse before the tin is capped, 
put into a basket and pushed into the boiler, where it is some 
four minutes before the zone of boiling water is reached. It was 
considered that an interval of ten minutes would completely 
cover this interval, and, accordingly, in another laboratory-test, 
the container was allowed to stand for ten minutes after receiving 
the boiling syrup, and before it was put into the boiling water. 
Even with the ten-minute interval before placing the tin in 
the boiling water, the fruit and the syrup were well over 70° for 
at least 25 minutes, and this should be enough to destroy all 
vegetating yeasts and bacteria. 
A number of faulty tins, ten in all, were received in October, 
1916. They consisted of pears, greengages, and plums. They 
were examined bacteriologically, and no growths were obtained 
from the contents of seven. A tin of pears contained a small 
active yeast, Saccharoinyces Zopfii, which has been shown to be 
responsible for the "puffing" of tins of golden syrup in America. 
412 THE SPRINGING OP TINS OF PRESERVED FRUIT, 
It actively fermented fruit-syrup, and was undoubtedly the cause 
of the springing of this particular tin. Another tin of pears 
contained a mixture of inactive yeasts and moulds. As the}' 
did not ferment fruit-syrup, it was clear that the cause of the 
trouble had disappeared. A tin of greengages contained inactive 
bacteria and moulds, and, as in the previous case, the agent 
which had caused the fermentation had died or had been killed. 
Several of the containers showed clear evidence of having leaked 
at some time. 
A second lot of six faulty tins of pears was obtained in June, 
1917, and the notes upon these are as follows. 
No.l. The container had a faulty lid, the tinplate was spong\', 
and foaming syrup was oozing out of a central pin-hole. 'J'he 
syrup was actively fermenting and contained yeasts. 
No.2, The container had a small quantity of syrup, the bulk 
having apparently leaked out. The syrup contained yeasts and, 
when set aside under aseptic conditions, it fermented vigorously. 
No. 3. The contents appeared to be normal, but the syrup con- 
tained bacteria and yeasts. 
No. 4. The fruit appeared normal, but the syrup was thin, and 
contained bacteria and yeasts. 
Nos.5 and 6. The contents were normal, and the syrup con- 
tained bacteria only. 
All the containers, with the exception of No. 6, showed signs 
of having leaked at some time. No. 6 was the only one that ap 
peared to be intact. 
The bacteria in the tins were the same. On dextrose ajjar, 
they grew as short, irregular rods, and hs chains, especially in 
the condensed water. They were Gram-positive, and, as they 
had no action upon any sugar, they could not have been respon- 
sible for the springing of the retainers. 
The yeasts w^ere all of the culture-type, that is, they were 
varieties of Saccharomyces cereinsice. This type is associated 
with the manufacture of beer, and one would not expect to find 
it in a factory where there is so much fruit utilised. In a factory 
such as a fruit-cannery, wild yeasts and torulse should be present 
in abundance, and it certainly was extraordinary to find only 
BY W. W. i/eSTRANGE AND R. GREfG-SMlTH. 413 
culture- or beer-yeasts in the preserved pears. It was subse- 
quently discovered that, adjoining the cannery, there is a factory, 
where a large amount of ginger-beer is produced. It is safe to 
conclude that the yeasts came from this source. 
In October, 1917, a third lot of six tins of pears was examined, 
and, with one exception, all of them showed signs of leakage. 
The contents were sterile, and, from the presence of soldered 
vent-holes on two of the containers, it was concluded that the 
lot had been reprocessed, that is to say, they had been put 
through the boiler after evidence of springing had been detected. 
One of the tins contained a strongly foaming, sterile syrup, and 
as this was oozing from one of the ends, it was evident that the 
re-processing had been of recent date. 
We had an opportunity of inspecting the processing of pears 
in February, 1918, and, from our observations, we concluded 
that the root of the trouble lay with the closing of the containeis. 
l he margin of the lid is painted with a mixture containing Hour 
or starch, and when the closing machine overlaps the edges of 
lid and container-top, the mixture fills up the spaces between 
the interlocked edges. The joint appears to be tight, and doubt- 
less the starchy mixture makes a good lute. But the pressure 
exerted by the air contained in the tin (it constitutes from one- 
twelfth to one twenty-fourth of the contents) must be consider- 
able during the passage of the container through the boiler. The 
luting mixture is supposed to form a jelly in contact with the 
hot water, on the one side, and the hot syrup on the other, and 
it is quite reasonable to suppose that the jelly may be forced out 
of the joint by the pressure of the contents. The tins appear to 
be sound immediately after processing: it is when they are 
stacked in the store-room, that they show signs of leakage. In 
the case of pears, about every second tin leaks more or less; 
with plums, about every tenth tin is faulty; and, with peaches 
and apricots, the leaks are few in number. As the processing is 
the same in all cases, one is driven to the conclusion that the 
juice of pears and, in less degree, that of plums, has a solvent 
action upon the luting jelly, and that another mixture should be 
employed. 
414 THE SPKIVGING OF TINS OF PRESERVED FRUIT. 
The experimental evidence shows that the duration and tem- 
peiature of the processing are suflBcient to absolutely free the 
contents from active yeasts. Their entry into the containers is 
most likely to occur while the tins are cooling down or shortly 
after. It is reasonable to suppose that the original air of the 
tin has been partly or entirely expelled during processing, and 
the vacuum created during cooling draws in the air of the factory 
with its suspended yeasts and other organisms. It is entirely a 
matter of chance as to the number of organisms and the activity 
of the organisms that may be in the indrawn air. There 
may be none, or they may be inactive, and the tin will not leak. 
There may be one or more, and, if these are active gas-producers, 
the tin will " spring. ' It is quite possible that some of the tins 
might be so imperfectly closed that they would leak under any 
circumstances, but the scarcity of leaks and springers among the 
tins of stone-fruits shows that this is of very rare occurrence. 
The behaviour of the pears and plums, as compared with 
apricots and peaches, points to the use of a more insoluble luting 
material, and, failing this method of overcoming the trouble, 
there is the alternative and probably better plan of allowing the 
tins to cool after processing in a current of filtered, sterile air, 
and, when cold, painting the joints with a lacquer- varnish. Thus 
the entry of yeasts into the tins would be prevented during the 
cooling, and the varnish would make them germ-tight and germ- 
proof.