Process development for continuous crystallization of fat under laminar shear

A novel continuous laminar shear structuring crystallizer with a suitable cooling system was designed and built. This is a new method to continuously crystallize edible fat in the desirable polymorphic form from the melt while being uniformly sheared. The machine consists of four main sections: Feed unit, shearing mechanism, cooling system and power unit. In each of these sections specific design considerations are taken into account which makes the process controllable and continuous. The shearing unit is made of two concentric cylinders. The internal cylinder is stationary and has a cooling system inside for temperature control. The outer cylinder rotates to produce a uniform shear in the sample fluid placed in the 1.5 mm gap between the cylinders. The sample's feed rate is controlled while it is pumped to the gap. The cooling system has three segments and provides an individual temperature gradient for each region. Cocoa butter and a binary mixture of cocoa butter and milk fat were crystallized from the melt under shear and different cooling regimes. A major modification in the samples phase transition behavior was observed; laminar shear induces acceleration of phase transition from less stable polymorphic form to the more stable form, beta(v). Moreover, X-ray diffraction patterns clearly showed crystalline orientation of the samples. This machine may open up new avenues for processing and manufacturing chocolate, shortenings and margarine. (C) 2008 Elsevier Ltd. All rights reserved.