The Formation of a 12-Hydroxystearic Acid/Vegetable Oil Organogel Under Shear and Thermal Fields
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ORIGINAL PAPER
The Formation of a 12-Hydroxystearic Acid/Vegetable Oil Organogel Under Shear and Thermal Fields Edmund Co • Alejandro G. Marangoni
Received: 13 October 2012 / Revised: 29 November 2012 / Accepted: 12 December 2012 Ó AOCS 2012
Abstract External laminar oscillatory shear applied during crystallization in combination with different temperature fields was used to modify the microstructure and physical properties of edible oil organogels. Crystallization at a high cooling rate (30 °C/min) resulted in a spherulitic microstructure with a higher oil-binding capacity, lower storage modulus and lower yield stress compared with a material (with a fibrillar microstructure) crystallized at a slow cooling rate (1 °C/min). The application of an oscillatory shear resulted in the formation of novel microstructures depending on the cooling regime used. The application of an oscillatory shear (strain [ 500 % and frequency = 1 Hz) resulted in the thickening of fibers observed in the slow-cooled material and an increased incidence of spherulite nucleation in the rapidly cooled material. Increasing the frequency of the oscillatory shear applied did not change the microstructure for the slowcooled gel but further increased the incidence of nucleation for the rapidly cooled gel. The application of controlledstrain oscillatory shear to the crystallizing gel at either cooling rates resulted in an oily and very soft, paste-like material. This material had a lower storage modulus and poorer oil-binding capacity compared with the same gel crystallized statically. Reduction of the oscillatory strain from a maximum of 1500 to 500 % moderately mitigated the loss of mechanical properties and oil-binding capacity
Electronic supplementary material The online version of this article (doi:10.1007/s11746-012-2196-6) contains supplementary material, which is available to authorized users. E. Co A. G. Marangoni (&) Department of Food Science, Ontario Agricultural College, University of Guelph, Guelph, ON N1G 2W1, Canada e-mail: [email protected]
although these properties were in no way comparable to those obtained from static crystallization. The study shows that the application of oscillatory shear and different cooling regimes can be used to tailor a crystalline organogel. However, the application of continuous shear must be done with care as application of excessive shear can result in a complete breakdown in gel structure and large amounts of oil loss. Keywords Modified fatty acids Vegetable oil Organogel Shear
Introduction There is a recent trend within the food manufacturing industry of minimizing the use of fat and lipid ingredients containing saturated and/or trans fatty acids while simultaneously switching to ingredients that contain high amounts of unsaturated fatty acids [1, 2]. This trend is due to the perceived negative health effects believed to be associated with the ingestion of high amounts of saturated and trans fatty acids as well as the touted health benefits of consuming dietary fat predominantly in t
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