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. 



