Antimicrobial activity and stability of Satureja khuzestanica essential oil pickering emulsions stabilized by starch nanocrystals and bacterial cellulose nanofibers

Pickering emulsions containing Satureja khuzestanica essential oil (SKEO) (O/W, 30:70) were produced by starch nanocrystals (SNCs) and bacterial cellulose nanofibers (B-CNF) as stabilizers. Heat acid hydrolysis method using different volumes of hydrochloric acid (0.8, 1.6 and 2 mL) was used to prepare SNCs from octenyl succinic anhydride starch. Characterization of SNCs by FT-IR and XRD revealed a lower increase in crystallinity by increasing acidity of hydrolysis solution. SEM results showed platelet-like fused nanocrystals with numerous surface pores after acid hydrolysis. Droplet size and absolute & zeta;-potential of SKEO emulsions stabilized by each of the SNCs (SNC-0.8, SNC-1.6 and SNC-2) and different B-CNF concentrations (0, 2, 4 and 8%) were evaluated. Results showed a downward and an upward trend from SNC-0.8 to SNC-2 and 0% B-CNF to 8% B-CNF, respectively. The viscosity of emulsions stabilized by combination of SNCs and B-CNF was higher than those without B-CNF. Besides, SNCs with higher degree of acid hydrolysis produced Pickering emulsions with lower viscosity. No significant changes were observed in the antimicrobial activity of SKEO emulsions stabilized with and without B-CNF against Staphylococcus aureus and Salmonella enterica in disk diffusion test, indicating that addition of B-CNF has no effect on antimicrobial properties. However, highest antibiofilm activity against mentioned bacteria was observed in emulsions stabilized by SNC-0.8. This study correlated the preparation method of SNCs and B-CNF addition on physical and antimicrobial properties of SKEO emulsions which could be used as safe and food grade systems for the delivery of EOs in the food industry.