in land animals it is progressively reinforced
with age. Meat collagen is tough and must be
cooked for some time near the boil to be
dissolved into gelatin, but in most fish it
dissolves at 120 or 130ºF/50–55ºC, at which
point the muscle layers separate into distinct
flakes.
Succulence from Gelatin and Fat Both
gelatin and fat can contribute an impression of
moistness to fish texture. Fish with little
collagen — trout, bass — seem drier when
cooked than those with more — halibut,
shark. Because the motion for steady
swimming comes mostly from the back end of
the fish, the tail region contains more
connective tissue than the head end, and
seems more succulent. Red muscle fibers are
thinner than white fibers and require more
connective tissue to join them with each other,
so dark meat has a noticeably finer, more
gelatinous texture.