β-sitosterol lipid nano carrier based on propolis wax and pomegranate seed oil: Effect of thermal processing, pH and ionic strength on stability and structure

The β sitosterol-loaded nanostructured lipid carrier (NLC) was formulated using propolis wax (PW) alone or in the mixture (1:1 w/w) with glyceryl behenate (GB), and pomegranate seed oil stabilized with Tween 80 and lecithin. The influence of thermal treatment (60-90ºC, pH 7, 20 min), pH (2, 4, 6 and 8) and ionic strength (0-200 mM NaCl, pH 7) on physical stability, structure and β sitosterol degradation was evaluated. The NLCs were physically and chemically stable during heating at low temperatures (≤70°C) while thermal treatment at 80-90 ºC led to an increase in size and a slight decrease in β sitosterol content. The particle size of PW and PW+GB NLCs increased from 96 nm and 105 nm at pH 7 to 108 nm and 114 nm at pH 2, respectively which may limit NLC long-term stability in highly acidic products. On the other hand, there was no significant difference in particle size and PDI with respect to electrolyte concentration. The NLC did not undergo polymorphic transitions by changes in pH and ionic strength. However, crystallinity decreased with increasing electrolyte concentration which was further confirmed by differential scanning calorimetry results. The β sitosterol NLC relatively showed a suitable potential for industrial applications. Practical applications: β sitosterol has many valuable physiological functions in human which has made it an attractive nutraceutical ingredient for food fortifications. Nevertheless, incorporation of β sitosterol in food and beverages is rather challenging since it is almost insoluble in water and only slightly soluble in oils. NLC based on PW and PSO offer a promising means for delivery of β sitosterol to aqueous-based foods and developing functional health promoting products by virtue of supplementary health benefits in addition to those of β sitosterol. However, functionality and dispersibility of formulations could be affected by environmental stresses typically experienced by foods during production and storage. Thus, behavior of www.ejlst.com European Journal of Lipid Science and Technology ccepte d A Article 3 emulsions at different conditions should be examined. NLC with relatively good physical and chemical stability to thermal processing, pH, and salt could be created using Tween 80 and lecithin as interfacial coating and PW as lipid matrix which ensures the successful delivery of β sitosterol to various food formats.