Caseinate-Stabilized Emulsions of Black Cumin and Tamanu Oils: Preparation, Characterization and Antibacterial Activity

Abstract

Caseinate-stabilized emulsions of black cumin (Nigella sativa) and tamanu (Calophyllum inophyllum) oils were studied in terms of preparation, characterization, and antibacterial properties. The oils were described while using their basic characteristics, including fatty acid composition and scavenging activity. The oil-in-water (o/w) emulsions containing the studied oils were formulated, and the influence of protein stabilizer (sodium caseinate (CAS), 1–12 wt%), oil contents (5–30 wt%), and emulsification methods (high-shear homogenization vs sonication) on the emulsion properties were investigated. It was observed that, under both preparation methods, emulsions of small, initial droplet sizes were predominantly formed with CAS content that was higher than 7.5 wt%. Sonication was a more efficient emulsification procedure and was afforded emulsions with smaller droplet size throughout the entire used concentration ranges of oils and CAS when compared to high-shear homogenization. At native pH of ~ 6.5, all of the emulsions exhibited negative zeta potential that originated from the presence of caseinate. The antibacterial activities of both oils and their emulsions were investigated with respect to the growth suppression of common spoilage bacteria while using the disk diffusion method. The oils and selected emulsions were proven to act against gram positive strains, mainly against Staphylococcus aureus (S. aureus) and Bacillus cereus (B. cereus); regrettably, the gram negative species were fully resistant against their action.

The Bioactivity and Physicochemical Properties of Emulsions Based on Tamanu, Moringa, and Inca Inchi Oils

“…The destabilization of the emulsion was a direct result of the oil content since the amount of the emulsifier added was constant. Referring to the studies conducted for emulsions with tamanu oil and casein, it can be concluded that the use of a larger amount of stabilizing agent with an increase in oil concentration has a beneficial effect on the obtained creaming index value [ 15 ]. Due to the emulsifier used, lecithin showed better stabilizing properties.…”

“…Additionally, studies on emulsions with tamanu oil indicate its poor emulsifying properties. It has been shown that oils with high viscosity tend to form emulsions with a larger particle size [ 15 ]. The most viscous of the oils applied is tamanu oil, which is roughly four times more viscous than inca inchi oil [ 3 , 27 , 28 ].…”

“…The same surfactant was used by Musa et al [ 14 ] to emulsify moringa oil. In contrast, Urbánková et al [ 15 ] used a natural casein-based emulsifier to emulsify with tamanu oil, but this is the only paper describing the properties of such a system, in addition to not addressing the rheological properties of the emulsion. In the case of inca inchi oil, the only paper on its emulsion with natural stabilizers (maltodextrin and a modified starch) is that published by González-Cardozo et al [ 16 ].…”

Thermal Properties of Novel Phase-Change Materials Based on Tamanu and Coconut Oil Encapsulated in Electrospun Fiber Matrices

“…For tamanu oil emulsions (Figure 3c,d), a slight thermal shift in the range of 0.06-2.2 • C between the melting and solidification curves occurred. Urbánková et al [45] studied tamanu and black cumin oil emulsions with the addition of sodium caseinate, and observed an average emulsion size in the range from 0.3 to 1.5 µm. In the current study, the average emulsion size of tamanu oil with Tween 20 (Figure 6) and Tween 80 (Figure 7) was 5-16 and 8-17 µm, respectively.…”

Polymer Biointerfaces

“…The oils and selected emulsions were proven to act against Gram-positive strains, mainly against Staphylococcus aureus and Bacillus cereus. Regrettably, Gram-negative species were fully resistant to their action [30].…”