Amino-acid composition of heated oyster shells

More than 90% of the protein in the shells of the modern oyster, Ostrea angelica, is decomposed when shells are heated at 130 degrees for 1 week. There remains, however, a stable residue that is little changed as heating is continued for 9 weeks. This residue resembles, in both amount and composition, the material previously recovered from fossil oyster shells deposited before the Pliocene era.