Abstract
THE cleansing of oysters on a commercial scale has now been accomplished after a period, of some fifteen year's continuous research work at the Conway Experimental Station of the Ministry of Agriculture and Fisheries. A purification station has been established at Brightlingsea, and since May has produced ‘certified’ American and Portuguese oysters. The principles of the process are almost the same as those involved in the cleansing of mussels, namely, a thorough preliminary cleansing of the outside of the shell is followed by a first and then a second bath in sterilised water. During immersion in the baths the oysters cleanse themselves internally and externally (that is, the external soft parts inside the shell) of bacteria in a simple way; the internal bacteria are expelled from the gut in the faeces, the external in mucoid films which are gleaned from all parts by cilia to be collected and extruded in masses as pseudo-faeces. After each bath, the shells are thoroughly washed to remove the excreta and are finally treated with water containing three parts in a million of free chlorine to destroy any remaining adherent germs. An essential feature of the oyster-cleansing process consists in the use of water at a temperature not less than 56 ° F., as it was found after a long series of experiments that ciliary activity below this temperature could not be relied upon to effect perfect cleansing. Mussels can be reliably purified in water which does not fall below 39 ° F. The English native (or European) oyster (Ostrea edulis) has been purified in a process involving three baths, and differs otherwise in its reactions from the American and Portuguese. It is reported that purified O. edulis may be produced in the coming winter. The summer capacity of the tanks is 360,000 oysters per week, but in winter when the sea-water requires to be warmed, the capacity is halved. Full details of the process and the plant are not yet available, but may be published in the near future.
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Cleansing of Oysters. Nature 134, 412 (1934). https://doi.org/10.1038/134412a0
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DOI: https://doi.org/10.1038/134412a0