On Food and Cooking

quickly. Japanese researchers have peered
through the microscope and identified the
likely culprits: the enzymes and other
proteins in muscle cells that are not locked
in the contracting fibrils, but float free in
the cell to perform other functions. These
proteins generally coagulate at a higher
temperature than the main contractile
protein myosin. So when myosin
coagulates and squeezes cell fluids out,
these other proteins flow out with the fluid.
Some of them then coagulate in the spaces
between the muscle cells, where they glue
the cells together and prevent them from
sliding easily apart when we chew. Highly
active swimmers like tunas and billfish
require more enzymes than sedentary
bottom fish like snappers and cod, so their
fibers get glued more firmly to each other
if they are cooked to 130ºF/55ºC and
above.