The antioxidant activity of Eryngium campestre, Froriepia subpinnata, and Mentha spicata polyphenolic extracts nanocapsulated in chitosan (CS) and maltodextrin (MD), and incorporated in canola oil under accelerated oxidation condition was evaluated. The zeta potential of nanoemulsions coated with 10%MD, 9.5%MD:0.5%CS, 9%MD:1%CS, and 8.5%MD:1.5%CS was −7.51 to −7.68, −0.06 to −0.08, 1.20 to 1.25, and 1.85 to 1.89 mV, respectively, also the average particle size was 52.73–52.91, 50.33–50.73, 26.05–27.29, and 15.78–15.92 nm, respectively. The highest (>91%) and lowest (70%–75%) encapsulation efficiency of the extracts obtained for 8.5%MD:1.5%CS and 10%MD, respectively. IC50 (DPPH assay) and EC50 (FRAP assay) of 8.5%MD:1.5%CS‐treated samples were the lowest among the different formulations. The E. campestre extract nanoencapsulated with 8.5%MD:1.5%CS had the best antioxidant capacity in canola oil, followed by 9%MD:1%CS, 9.5%MD:0.5%CS, and 10%MD. In the conclusion, the encapsulation with 8.5%MD:1.5%CS is suggested as an efficient coating formulation to enhance the antioxidant efficacy of the extracts.
Practical applications
Despite the great potential of herbal extracts as food antioxidants and antimicrobials, low solubility in oil and high volatility of phenolic compounds cause problems in their usage. To protect hydrophobic bioactive compounds against processing conditions in food preparation, increase their solubility and stability in the food matrix, and prevent undesirable flavors, nanoencapsulation, and nanoemulsifying of herbal extracts are used. Due to the small size, transparency, and high thermodynamic stability against precipitation and accumulation in food complex, nanoemulsions are most preferred. So, the results of this work will help design the proper formulation of coatings for bioactive compounds applied in the food industry.
