Abstract: A multiple-use injection machine of the type used in food processing, is especially suited for selectively injecting treatment media into meat products including, inter alia, beef, pork, whole chickens and chicken parts. The treatment media is chose from a group including both liquid aqueous solutions utilized at normal ambient temperatures and normal operating pressures and a thermal treatment medium such as live steam at elevated temperatures and pressures.

Abstract: A back-flushing method is practiced with a back-flushing filter construction wherein a perforate filter screen providing filter openings also forms an internal chamber for receiving the effluent from a liquid stream. A filter piston is disposed in the internal chamber and operates to divide the chamber into first and second zones on opposite sides of the piston. By selectively reciprocating the piston, the effluent in the chamber is compressed and moved on both sides of the piston. Thus, the effluent back-flushes the filter openings and creates a rolling action in the liquid surrounding the filter screen on the upstream side to dislodge particulate debris accumulated on the filter screen.