No. 2 (1921) REMARKS ON CANNING 123 



under the soldering iron of steam which forces its way through 

 the fluid solder ; hence it is usual to put in brine after the top is 

 soldered ; tipping is easy enough since it merely means a drop or 

 blob of solder on a small hole. With solderless cans this diflfi- 

 culty does not arise. 



191. Wet packed prawns require shorter processing than when 

 dry packed, since the convection currents in the fluid rapidly 

 transmit heat to all parts of the contents. But dry packing is more 

 practised than wet. In an American official pamphlet No. I cans 

 dry packed with only 4%, oz. of prawns are said to be processed 

 for I hour at 240^ F., while wet packed only require II minutes. 

 This has not been tested, but at Beypore the cylindrical flats in 

 which about 9 oz. of prawns are usually packed " dry " get up to 40 

 to 45 minutes, and this is found to be ample. 



Curried prawns are in favour; these require merely an addition 

 of curry mixture to the ordinary packing, 



192. Oysters. — These are always packed in fluid. Only a few 

 experiments have been made at the Government cannery and these 

 were not continued partly for want of good material close at hand, 

 partly because the contents of the cans, though perfectly sound, 

 generally assumed a green colour inside the fish, probably due to 

 the food of the fish. Much experiment is required to ascertain 

 the best sort of cannable oyster and the best mode of condition- 

 ing oysters intended for canning. 



193. The general practice is as follows :— On receipt the oysters 

 are well washed to get rid of adherent mud, etc., and are then 

 opened. The older fashion was to open by hand which is slow 

 and productive of small fragments of shell of which it is difficult 

 to get rid. The modern practice is to place the shells, round side 

 downwards, on trays which again are placed in cars or trollies; 

 these are run into horizontal steam chests or retorts, which are 

 then closed and steam turned on at about 10 lb. pressure for 5 or 

 more minutes, according to the size and thickness of the shells 

 or the incrustations on them. On removal from the chest, the 

 oysters are found to be gaping so that the meats can be easily 

 removed with a short blunt knife ; since the oysters are placed with 

 the convex side downward the natural juice is retained in the deep 

 shell and this is carefully removed, passed through a muslin sieve 

 to remove fragments, and set aside to add to the packed oysters. 

 It is stated that if oysters have to be kept over-night for packing,. 



