If you’ve ever tried opening a fresh oyster, you will know just how difficult that can be. You need just the right sort of knife with a short and very stout blunt blade and guard. You also need something to protect your hand while you attempt to prise the two valves apart. It also helps if you know just how to do it and have a lot of practice.
The trick, with the European Flat Oyster at least, is to break the ligament from the outside of the shell using the point of the blade first to relieve some of the tension created by the tremendous muscular pull within the shell that holds the two valves together. If you can achieve this, the following stage is a bit easier.
The next thing is to insert the knife between the two shells at the edge of the oyster. The idea is to keep the flat of the blade parallel and right up against the inner surface of the flat or right valve. You use the point of the blade to feel for the position of the strong adductor muscle which is contracting and holding the oyster shut. Once this is located, you can cut through it and open up the oyster. Easier said than done, actually.
It is easy to imagine that the margins of the shells might get damaged in the opening process – especially if the knife has been twisted to prise the valves apart. The first three pictures in this post show oyster shells from excavations of archaeological sites in Poole, Dorset, UK, dating from early medieval times. These were found still in their original paired valves with V-shaped or W-shaped notches on the margins of the shell. It looks as if these notches were made by a knife or even by a type of pincers to open the oyster.
The fact that the shells were found in their original pairs indicates that the ligament was not broken as a preliminary. The marginal notches are evidence for the fact that the oysters were opened while they were still alive. If they had first been steamed, boiled, or roasted, the oysters would have gaped in the heat and no tools would have been required to open them.
The last three pictures show the inner surfaces of oyster shells from archaeological excavations of a Saxon site in Southampton, Hampshire, UK. There are sharply defined cut marks in the soft white surface of each specimen. In two shells these are straight lines and in one shell they form a series of parallel arcing lines. These are most likely to be marks left by a knife, probably one in which the edge was no longer honed but rough and irregular, as the oyster shell was opened and the meat was scraped from the shell.
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