Impacts of various mixing approaches towards black seed oil-alginate emulsion attributes

Abstract

Black seed oil (BSO) contains thymoquinone, an active ingredient that is well-known for its antioxidant property. The bitter taste of BSO makes it challenging for the consumers, mainly children and the elderly, to consume it every day. Thus, BSO is encapsulated in alginate beads in micrometre size to enhance its palatability. This encapsulation was previously established in the lab-scale and the standard mixing method to produce a stable BSO-alginate emulsion used a magnetic stirrer coupled with a sonicator. This mixing method is not suitable for the production of BSO beads at a large scale. Hence, this research aims to investigate the impacts of various mixing methods coupled with sonication towards the BSO-alginate emulsion attributes. Four BSOalginate coarse emulsions were prepared using a magnetic stirrer (MS) as the benchmark, overhead stirrer (OS), homogeniser (H), and overhead stirrer combined with homogeniser (OSH). All the coarse emulsions were then sonicated to produce a nanoemulsion using a flow cell sonicator. The coarse emulsions were characterised in terms of dissolution time while the nanoemulsions were characterised in terms of droplet size, polydispersity index, zeta potential, conductivity and absorbance. These characteristics were statistically compared to the benchmark emulsion characteristics. MS, OS, H, and OSH coarse emulsion formation required 45, 230, 102, and 46 minutes to be produced, respectively. There were significant differences (p <0.05) between the droplet size of OSH (266.53±4.36) nm and MS (285.50±1.15) nm emulsions, indicating that the OSH emulsion was more stable. The absorbance of OSH BSO-alginate nanoemulsion was significantly lower (p <0.05) than the benchmark. In comparison to MS as the benchmark, OSH technique produced a stable emulsion in terms of lower dissolution time, droplet size, zeta potential, and absorbance.