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

Abstract

Phytosterols can lower LDL-cholesterol and are frequently used by the functional food industry. However, little is known regarding how phytosterol crystallisation can be controlled, despite solubilised phytosterols having improved bioaccessibility. This study investigates phytosterol crystallisation in bulk milk fat and in model dairy emulsion systems at two average droplet sizes, 1.0 and 0.2 µm. The effect of lecithin and monoacylglycerol addition on phytosterol crystallisation for both emulsion and bulk systems was also evaluated. Results demonstrated that lecithin and monoacylglycerols enrichment into the bulk system minimised phytosterol crystallisation. However, in emulsions, phytosterol crystallisation was mainly influenced by decreasing the droplet size. Smaller emulsion droplets containing lecithin showed the greatest potential for decreasing phytosterol crystallisation and had improved physicochemical stability. This information can be employed by the functional food industry to minimise phytosterol crystallisation and possibly improve bioaccessibility.

Physical and interfacial characterization of phytosterols in oil-in-water triacylglycerol-based emulsions

“…Decreases in particle size have been observed previously with phytosterol enrichment in milk fat-based emulsions (Zychowski et al, 2016). Statistically significant decreases in particle size have been observed previously with phytosterol enrichment in milk fat-based emulsions (Zychowski et al, 2018;Zychowski et al, 2016). The overall droplet size distribution ranged from 0.1 to 16.4 µm (Fig.…”

“…Emulsions were prepared by homogenization with an APV 1000 homogenizer (SPX flow, Germany) at 300 bar pressure for 1 pass at 60°C. Higher pressures or more passes were not employed within this study as more intense treatments yielded smaller droplets, which were unsuitable for microscopic evaluation (Zychowski et al, 2018). Emulsions were allowed to statically cool and were stored at 20-25°C with 0.1% sodium azide added to the final emulsion.…”

“…droplet sizes to observe significant differences in stability (Zychowski et al, 2018). Interestingly, no significant difference was observed in stability upon the addition of phytosterols into the emulsion systems; typically, the presence of crystals within an emulsion system causes emulsion destabilisation, by means particle coalescence of the lipid droplets (McClements, 2012).…”

“…In a follow up study by the Zychowski et al (2018), emulsions with lecithin and whey protein were found, using synchrotron X-ray scattering, to prevent phytosterol crystallisation to a greater degree than phytosterol and whey protein emulsions without lecithin alone.…”

β-Sitosterol Loaded Nanostructured Lipid Carrier: Physical and Oxidative Stability, In Vitro Simulated Digestion and Hypocholesterolemic Activity

“…The remarkable stability profile of the emulsions was also attributed to the surface activity of β-sitosterol that reduces the interfacial free energy at the interface, and thus renders some degree of stability to the resulting emulsion system [23]. Furthermore, in studies performed by Chen et al (2016) and Zychowski et al (2018), phytosterols have been found to improve the overall stability of the oil in water emulsion over time [24,25]. Figure 2 represents the chemical stability of the NLCs at different temperatures over time in terms of their β-sitosterol content.…”