Effects of Shear Rate Variation on the Nanostructure of Crystallizing Triglycerides

Abstract

Shear flow affects the kinetics of crystallization and modifies the composition of the solid and liquid phases obtained during crystallization. Research on the effects of shear flow on the crystallization is necessary to understand how triglycerides form crystalline structures. In this Article, palm oil, milk fat, and milk fat triglycerides were cooled at 3 or 0.5 °C/min from the melt at 50 °C down to 17.5 or 17 °C and left to crystallize under a shear rate of 90 s À1 in a Couette cell system. The shear rate was then increased to 1440 s À1 . Synchrotron X-ray diffraction patterns were captured during the crystallization process. The integrated intensity, average thickness, and average lamellar spacing of the crystalline nanoplatelets were modified by the shear rate step. Increased thickness and crystalline orientation were evident after the shear rate step-up. Similar experiments with milk fat in a Rheo-NMR instrument provided additional information to interpret the orientation and thickness changes observed. These effects of shear step-up on crystallizing fats offer new options for the industrial processing of chocolate, dairy, margarine, and shortening production, allowing more freedom for tailoring their desired crystalline nanostructures.

Rheological characterization of triglyceride shortenings

“…The possibility of higher structural ordering is qualitatively supported by our previous wide-angle X-ray scattering analysis which displayed sharper Bragg's peaks for roll-in shortenings (Macias-Rodriguez and Marangoni 2016). Further evidence is provided by several accounts in the literature demonstrating that shear accelerates polymorphic transitions and orients fat crystallites at the molecular and mesoscale levels, respectively (Mazzanti et al 2011;Maleky et al 2011).…”

Effects of external shear forces on crystallisation kinetics of model fat blends

“…In contrast to samples crystallised under static conditions, shear crystallisation created a crystal network of a large number of small crystals (3.2 ± .1.69 μm) evenly distributed and tightly packed together. These findings are in agreement with those of previous studies, which reported the presence of larger crystals when crystallisation was conducted under static conditions (Chaiseri & Dimick, ; Sonwai & Mackley, ; Marty & Marangoni, ; Maleky & Marangoni, ; Mazzanti et al ., ).…”

Physical properties of fats in food

“…Since this review was published, more detailed work on cocoa butter and milk fat has been reported by many groups (MacMillan et al, 2002;Mazzanti et al, 2003Mazzanti et al, , 2007Mazzanti et al, , 2008Mazzanti et al, , 2009Mazzanti et al, , 2011Padar et al, 2009). In these studies, it was evident that the rates of polymorphic crystallisation and transformation were largely increased by applying shear.…”

“…• clarification of formation mechanisms of mesoscale and macroscale fat crystal network starting from nanoscale primary fat crystals (Acevedo et al, 2011); • rheological and texture properties that are dominated mainly by fat crystal networks (Boode et al, 1991;Marangoni and Hartel, 1998;Marangoni et al, 2012;Walstra et al, 2001); • influences of external factors such as shear, ultrasound irradiation, minor lipids on fat crystallisation kinetics (Martini et al, 2008;Mazzanti et al, 2011;Smith et al, 2011;Wright et al, 2000).…”