meat can be quite tough, in part because they apparently accumulate connective-tissue collagen as an energy reserve! Either very gentle or prolonged heating is essential; the meat toughens badly when it exceeds 120ºF/50ºC, and the collagen shrinks and compacts the tissue Once this happens, continued simmering will eventually dissolve the collagen into gelatin and make the meat densely silken Japanese cooks simmer abalone for several hours to obtain a more savory flavor (free amino acids apparently react to form taste-active peptides) Clams Clams are the burrowing bivalves They dig themselves into ocean or river sediments by extending a foot muscle downward, expanding its end into an anchor, and then contracting the foot while squirting water and rocking the shell In order to reach the water from their burrow to breathe and feed, they have a pair of muscular tubes or “siphons,” one for inhaling and the other for exhaling, which may be separate or else joined together into a single “neck.” The U.S term “hard shell” is applied to sturdy clams that close completely (littleneck, quahog), while “soft shell” clams have siphons much longer than the shell, which is thin and always gapes (steamer, longneck) The Japanese or Manila hard-shell clam (Ruditapes philippinarum) is the only one to be cultivated on a large scale worldwide, thanks to its robustness and preference for shallow burial The other dozen or so common clam species are mainly regional products Some species of the large surf clam (Mactromeris species) absorb plankton pigments and have a striking red layer on several muscles The largest and most grotesque of the temperate commercial clams is the deep-burrowing geoduck of the Pacific Northwest subtidal mudflats (Panope generosa), whose neck looks like a small ... Some species of the large surf clam (Mactromeris species) absorb plankton pigments and have a striking red layer on several muscles The largest and most grotesque of the temperate commercial clams is the deep-burrowing geoduck of the Pacific... sturdy clams that close completely (littleneck, quahog), while “soft shell” clams have siphons much longer than the shell, which is thin and always gapes (steamer, longneck) The Japanese or Manila hard-shell clam (Ruditapes philippinarum) is the only one to... (Ruditapes philippinarum) is the only one to be cultivated on a large scale worldwide, thanks to its robustness and preference for shallow burial The other dozen or so common clam species are mainly regional products