What it actually is
Heat denatures the protein network and makes it contract. As it contracts it squeezes out the water it was holding between the filaments. How much leaves depends on how well that water was held in the first place and how severe the heat step is.
Why it matters
It is the most direct yield number in a meat plant. Water that leaves is weight already bought and no longer sellable, and it leaves as drip in the pack as well as as steam in the oven. A point of cook loss is a point of margin.
What changes it
pH relative to the isoelectric point, salt level, how much myofibrillar protein was solubilised, the rate and endpoint of cooking, and the quality of the raw material. Phosphate acts on the first three at once, which is why removing it moves this number so sharply.
