Effect of Phytosterols on the Crystallization Behavior of Oil-in-Water Milk Fat Emulsions

Abstract

Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.

Phytosterol crystallisation within bulk and dispersed triacylglycerol matrices as influenced by oil droplet size and low molecular weight surfactant addition

“…After heating, the WPI solution was mixed with Milli-Q water at 70 °C to create a 1% protein solution. This process, as employed previously, was utilised to minimise denaturation of the whey protein caused by excessive heating or high temperatures (McClements, 2004;Zychowski, et al, 2016).…”

“…In this equation, a is the maximum height of the diffracted peak, b is the peak position, and c is the full width at half-maximum (FWHM) of the peak, as used previously for SAXS/WAXS analysis (Zychowski, et al, 2016).…”

“…Promising research has also shown that milk enriched with phytosterols (1.8 g/day) using a proprietary crystal-retardation method can result in a 29.1 ± 4.1% reduction in LDL-cholesterol levels (Pouteau, Monnard, Piguet-Welsch, Groux, Sagalowicz, & Berger, 2003). In a previous study by the authors, the underlying mechanism of phytosterol crystallisation within milk fat matrices was examined (Zychowski, Logan, Augustin, Kelly, Zabara, O'Mahony, et al, 2016). However, to date, no work has explored possible ways to decrease phytosterol crystallisation within a milk fat system.…”

In Vitro Bioaccessibility of Low‐Crystallinity Phytosterol Nanoparticles Generated Using Nanoporous Starch Bioaerogels

“…Considerable efforts have been recently dedicated to improving the solubility and/or bioavailability of phytosterols. So far, chemoenzymatic modifications (He et al., ), emulsion formulations (Fisher, Wachtel, Aserin, & Garti, ; Leong et al., ; Moschakis, Dergiade, Lazaridou, Biliaderis, & Katsanidis, ; Ribeiro et al., ; Rozner, Aserin, Wachtel, & Garti, ; Zychowski et al., ), formation of colloidal phytosterols by precipitation from organic solvents (Rossi, Seijen ten Hoorn, Melnikov, & Velikov, ), synthesis of cyclodextrin inclusion complexes (Meng, Pan, & Liu, ), cocrystallization of phytosterols and triacylglycerols (Acevedo & Franchetti, ), and microencapsulation by spray drying (Di Battista, Constenla, Ramírez‐Rigo, & Piña, ) have been used for decreasing the particle size and improving the solubility of phytosterols. However, long complicated chemical modifications, the use of toxic organic solvents and nonfood grade surfactants remain major obstacles with these methods.…”

Highly Efficient Synthesis of Hydrophilic Phytosterol Derivatives Catalyzed by Ionic Liquid

“…So far, little research has been reported to improve the solubility of phytosterols in water. Recently, some scholars attempted to improve the dispersity or solubility of phytosterols in water via a physical route (Cowins, Abimbola, Ananaba, Wang, & Khan, 2015;Leong et al, 2011;Zychowski et al, 2016). Leong et al (2011) demonstrated the feasibility of phytosterol nanodispersions production using an emulsification-evaporation technique and the particle sizes were about 50 nm.…”