Influence of moisture movement on the muscular tissue during vacuum cooling of cooked meat

Vacuum cooling of cooked meat was carried out to investigate the fundamental principles of moisture movement by the variations of temperature field, evaporation rate and water content of cooked meat. In addition, the effect of moisture movement on the interior tissue structure of cooked meat was studied by using transmission electron microscopy (TEM). During vacuum cooling, it can be found from the experimental results that it took only about the first 4～5 min to reduce the surface temperature of the cooked meat from 63℃ to 10℃. Average water content of cooked meat decreased from 71% to 60.69%. For evaporation rate, there were two periods: an accelerating period and a falling period. Experimental results and theoretical analysis showed that moisture movement within cooked meat during vacuum cooling consists of two parts. One was water migration within cooked meat caused by chemical potential; the other was water vapour movement produced by evaporation or ebullition caused by pressure drop. At the same time, transmission electron microscopy observations revealed that morphology of muscular tissue at the surface and the core of cooked meat treated by vacuum cooling remained intact. However, muscle fiber separation and formation of large intercellular spaces occurred in the intact muscle fiber of muscular tissue treated by vacuum cooling.