A fat conditioning apparatus includes a conditioning vessel enclosing a conditioning chamber and a displacable plug. The conditioning chamber is bounded on one end by the displacable plug and has a variable volume that is a function of the position of the plug within the conditioning vessel. The apparatus has utility in a fat conditioning method, wherein the conditioning chamber contains a harvested fat emulsion. A washing liquid is injected into the conditioning chamber and mixes with the harvested fat emulsion, thereby displacing the plug in an outward expansion direction and expanding the variable volume of the conditioning chamber. The resulting mixture of harvested fat emulsion and washing liquid is stratified in the conditioning chamber into a contaminant-lean fat fraction and a contaminant-rich remainder fraction. The fat fraction, which is substantially free of the remainder fraction, is recovered from the conditioning chamber as a desired product of the method.