Process for the preparation of a polyolefin polymer by continuously polymerizing one or more olefin monomers in suspension at temperatures of from 40° C. to 120° C. and pressures of from 0.1 to 10 MPa in the presence of a polymerization catalyst in at least one polymerization reactor, comprising a) withdrawing a suspension of solid polyolefin particles in a suspension medium from the polymerization reactor, wherein the suspension has a temperature of from 65° C. to 120° C.; b) feeding the suspension withdrawn from the polymerization reactor to a moderating vessel; c) keeping the suspension in the moderating vessel at a temperature of from 60° C. to 85° C. for a time sufficiently long that the mean residence time of the suspension in the moderating vessel is at least 5 min; d) withdrawing suspension from the moderating vessel; e) cooling the suspension withdrawn from the moderating vessel to a temperature of from 20° C. to 55° C.; and f) mechanically separating the solid polyolefin particles from the liquid suspension medium, and method for controlling the content of hydrocarbons with from 14 to 300 carbon atoms in a polyolefin polymer prepared by polymerizing one or more olefin monomers in suspension.