The present study discusses the optimal crystal growth conditions required for the emulsion crystallization of hydrogenated castor oil (HCO) into several crystal morphologies. The best possible crystal shape is furthermore identified in case high rheology modifying performance is required. NCO was crystallized in a meso- and micro-continuous process which allowed for a controlled and fast screening of several crystal morphologies at different crystallization conditions. Applying high isothermal temperatures (above 55 degrees C) resulted in a combination of rosettes, thick fibers and thin fibers. At lower isothermal temperatures (below 55 degrees C) the shape gradually evolved to a combination of short needles, spherically shaped and/or irregularly shaped crystals. Crystals with the highest aspect ratio were obtained when crystals were grown between 30 degrees C and 45 degrees C and were subsequently reheated above 63 degrees C, forming high amounts of large thin fibrous crystals. When diluted to 0.25 wt% these fibrous crystals increased he low shear viscosity far better compared to the other crystal shapes. (C) 2013 Elsevier B.V. All rights reserved.