36 SHELLFISH CONTAMINATION FROM SEWAGE-POLLUTED WATERS. 



INSUFFICIENT COOLING. 



The proper cooling and subsequent refrigeration of any perishable 

 food product is highly essential to prevent rapid decay from bacterial 

 activity. The results obtained in a series of experiments on the keep- 

 ing qualities of oysters demonstrate that the proper refrigeration of 

 shucked oysters is necessary to retard deterioration. Even when 

 such oysters are kept at low temperatures above the freezing point 

 there is some bacterial development taking place, but this is reduced 

 to the minimum by a plentiful supply of ice. 



SOURING DUE TO AGE. 



The souring of oysters may occur because of the length of time 

 they are allowed to stand after shucking. Such oysters may have 



FIG. 14. Various types of containers for shipping oysters, as used by the trade. 



contained but few organisms originally when freshly opened, but 

 because of age alone they become unfit for use. There are always 

 enough bacteria present in oysters even when opened under the best 

 of sanitary conditions to cause spoilage after a certain interval of 

 standing. This length of time will depend upon the number and kind 

 of bacteria present and the temperature at which the oysters are 

 stored. This fact is well illustrated in fig. 15, showing the results of 

 two methods of keeping opened oysters. 



Shucked oysters are best when freshly opened, and they should be 

 consumed at the earliest possible moment after shucking, although 

 oysters grown on sanitary beds and handled under proper conditions 

 remain edible for several weeks, when unshucked, but their quality 

 does not improve with the length of time out of the shell. Illness 

 of a serious nature may result from eating stale shellfish. 



