Effect of Shear on the Rheology and Crystallization of Palm Oil

Abstract

ABSTRACT:This paper reports on the impact of shear on crystallisation upon cooling of palm oil.Samples were cooled down under shear from 70 °C to 10 °C, then kept at this temperature, while performing rheological measurements using a controlled shear rate rheometer and rheo-optical observations using optical microscopy and small-angle light scattering. Shear rates between 1 and 300 s -1 were investigated. Two crystallisation steps were observed, characterized by associated viscosity increases. The effect of shear on these two crystallisation processes was investigated. Shear was shown to influence almost all the steps of the structuring process of the crystallizing palm oil. The spherulite size and growth rate during the first crystallisation are affected by shear. The onset time of the secondary crystallisation process strongly depends on the extent of shear. The steady state structures after the first and the secondary crystallisation processes constituted of a suspension of aggregates of spherulites are controlled by the applied shear rate. PRACTICAL APPLICATION:The texture of crystallised vegetal fats and subsequent end product properties depend on the structure developed during the crystallisation process. This structuring process is strongly influenced by the thermo-mechanical history submitted to the product (cooling rate, degree of undercooling, annealing time, application of flow). This paper shows how the extent of shear affects the different steps of the crystallisation and aggregation processes in the case of palm oil after the first crystallisation.

Effect of Shearing on Crystallization of Palm Oil-Based Fat Blends

“…As mentioned at the beginning of the paper, there have been a number of recent reports on the crystallization of palm oil under shearing, and this subject has been well elucidated (Mazzanti et al, 2003, Mazzanti et al, 2005, De Graef et al, 2009, Tarabukina et al, 2009. However, the present study supplements these reports by providing further information on the long-term crystallization behavior of palm oil.…”

“…Syringe-extrusion method In the syringe-extrusion method, a 2-mL glass syringe was filled with a mixed fat blend and held at 80℃ before cooling. For rapid cooling, the syringe filled with the fat blend was covered with iced water for 2 min, held at 5℃ for 1 h, and then sheared by extruding 1995, Mazzanti et al, 2003, Mazzanti et al, 2005, Sonwai and Mackley, 2006, De Graef et al, 2009, Tarabukina et al, 2009; however, most of the research was focused on the effect of shearing on initial crystallization behavior. Commercially distributed fat food products are required to maintain their quality over weeks to months.…”

Effect of organogelator and fat source on rheological properties of olive oil-based organogels

“…For lower values, sample BM2 becomes more consistent and structured and a second slope change, indicating a potential second transition region, occurs because of the higher saturated fats content of cocoa butter with respect to olive oil, which gives hardness and elasticity to the oil phase at lower temperatures . The slope changes in G* curves can be explained by considering the fats crystallisation in different polymorphic crystalline forms Tarabukina, Jego, Haudin, Navard, & Peuvrel-Disdier, 2009). When the molten system is cooled down, fat crystals (in the α form) are obtained and their size and number increase with decreasing temperature; moreover, during the cooling process, potential transitions (α → β′ polymorphic transformation) and aggregations occur, yielding, finally, the formation of a three-dimensional crystalline network (Walstra, Kloek, & van Vliet, 2001).…”

Application of laser backscattering for monitoring of palm oil crystallisation from melt

“…Miskandar et al [10] examined the effects of cooling time on the crystal distribution of a blend of palm oil and palm olein using a combination of pulsed nuclear magnetic resonance (NMR) and PLM. Rheo-optical techniques have also been applied by De Graef et al [11] and Tarabukina et al [12] to study the effect of shear on crystals development in palm oil. A recent study by Vuillequez et al [13] used optical thermal analysis (OTA) on palm oil to investigate the effect of cooling rate variation on the crystal sizes.…”