No. 2 (1921) REMARKS ON CANNING 9l 



goods of same size, contents, etc., at the same time, even in the 

 open pan. 



114. Until standard periods for the several cans of various sizes 

 and contents have been arrived at by experience, some losses 

 must be expected. It is well, during such time, that the canner 

 should, especially where work is more or less experimental, adopt 

 the plan of enclosing small recording thermometers in the centre of 

 the marked cans and thereby ascertaining whether the entire 

 contents have reached the desired temperature; meanwhile the 

 paragraphs below dealing with the various classes of goods, will 

 give approximate standards. 



115. The methods of processing are widely different and must 

 be selected on a consideration of conditions ; all will, if properly 

 conducted, give perfect results in sterilisation, but all are not 

 equally convenient under different conditions. The first and most 

 simple method is that of processing in plain water in an open pan ; 

 in this method the temperature cannot possibly rise above 212*^ F". 

 and in case of large cans of poorly conducting contents the cans 

 have to be cooked for a very long time. This not only wastes 

 time and demands several boiling vats in simultaneous use if the 

 cannery or rush of goods is at all large, but is apt unduly to cook 

 the outer layers of the contents while the heat is penetrating to the 

 centre; for ordinary sardine quarters the period of boiling from 

 the time that the actual boiling point (212° F.) is reached in the vat 

 may be I/^ hours. But the method has the great advantage for a 

 small cannery of requiring the simplest and cheapest of plant ; 

 any metal pan over an open fire will readily effect the necessary 

 cooking, nor is any expensive boiler attendant necessary. Other 

 advantages exist, especially the fact that no strain is put on the 

 joints or seams by the iiiter/tal generation of pressure steam ; the 

 internal pressure is due solely to^the expansion of any air in the 

 can and if this has been properly 'exhausted,' or if the goods are 

 merely sardines in oil, the internal pressure is inconsiderable ; 

 hence much fewer leaks than where a high temperature and press- 

 ure are adopted, unless great care is exercised. Another advantage 

 is that testing, exhausting, and processing may be continuous in the 

 same vat, so that much time, labour, fuel, etc., can be saved. One 

 further advantage is that when the processing period is over, the 

 ebullition is stopped and if any of the cans are then leaky the fact 

 may be discovered before removal of the baskets from the boiling 



