Bound Water ? Water that is held very tightly to proteins. Heating to 100°C does not drive off this water nor is it frozen at temperatures down to ?40° C (-40°F). This water makes up a very small portion of the total water in muscle ? approximately 0.5% of the water in muscle is truly bound. Entrapped Water (also called immobilized water) ? Water that is held in muscle by being entrapped by the structural features of the muscle cell. For example water held in the myofibrils, and water held in the cell itself by the cell membrane (sarcolemma). Free Water ? Water whose flow from the tissue is unimpeded. This water makes up less than 10% of the total water found in pre-rigor meat.