Synchrotron study on crystallization kinetics of milk fat under shear flow

A detailed synchrotron X-ray diffraction study on the kinetics of crystallization of anhydrous milk fat (AMF) and milk fat triacylglycerols (MFT) was done in a Couette cell at 17 degrees C, 17.5 degrees C and 20 degrees C under shear rates between 0 and 2880 s(-1). We observed shear-induced acceleration of the transition from phase alpha to beta' and the presence of crystalline orientation, but no effect of shear on the onset time of phase alpha was observed. A two stage regime was observed for the growth of phase beta'. The first stage follows a series-parallel system of differential equations describing the conversion between liquid and crystalline phases. The second stage follows a diffusion-controlled regime. These mechanisms are consistent with the crystalline orientation, the growth of the crystalline domains and the observed displacement of the diffraction peak positions. The absence of the polar lipids explains the faster kinetics of MFT. (c) 2009 Elsevier Ltd. All rights reserved.