Whey protein isolate-guar gum stabilized cumin seed oil nanoemulsion

Cumin seed oil (CSO) nanoemulsions were prepared using an ultrasonication method with preheated 10% wt whey protein isolate (WPI) and 0.2% wt guar gum (GG) as an aqueous phase, and mix of CSO and corn oil (30:70) as an oil phase. The droplet size of the emulsion was about 75 nm. The physical stability of the emulsion improved significantly in the presence of GG (0.1–0.2% wt).

Based on FTIR analysis, interaction of reducing groups of GG with amino groups of WPI occurred through covalent attachment, which was verified using sodium-dodecyl-sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). The glycosylated fraction of protein was ∼110 kDa. Minimum bactericidal concentrations (MBC) of CSO nanoemulsions were 2.27 and 0.6 mg/mL against Staphylococcus aureus and Escherichia coli, respectively.

The killing kinetics assays showed that CSO nanoemulsions were able to kill these microorganisms after 15 and 5 min of incubation, respectively. In the case of Aspergillus flavus, the inhibition zone of CSO nanoemulsions with different concentrations of CSO (15, 5, 3 mg/mL) ranged between (32-10 mm) after 5 days of incubation at 25 °C.

Moreover, based on a cytotoxicity assay, CSO nanoemulsions showed good biocompatibility. It can be concluded that WPI-GG stabilized CSO nanoemulsions may have the potential to be used in food as an effective preservative.