Continuous laminar shear crystallizer to nanostructure edible fats.

摘要

A novel continuous laminar shear nanostructuring 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 driven by a controlled electromotor to produce a uniform shear in the sample fluid placed in the 1.5 mm gap between the cylinders. Sample's feed rate is controlled while it is pumped into the gap. The cooling system has three segments. Each segment, which is water jacketed, provides a separate temperature gradient for each region. The concept of separate water jackets provides smooth and precise temperature control during the crystallization process, which is usable in the crystallization of different fats. Cocoa butter was crystallized from the melt under different cooling regimes and shear rates. A major modification in cocoa butter phase transition behavior was observed; laminar shear induces acceleration of phase transitions from less stable polymorphic form to more stable forms. Moreover, X-ray diffraction patterns clearly showed crystalline orientation of the sample. This machine may open up new avenues for processing and manufacturing chocolate, shortenings and margarine.