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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 



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