Enterococcus hirae OL616073 glucan exopolysaccharide based cumin oil emulsion: Characterization and antibacterial activity

Abstract

This study aims to prepare the cumin essential oil-based emulsion stabilized by glucan exopolysaccharide (EPS) from Enterococcus hirae OL616073. The emulsion was prepared by optimizing different ratios of EPS to essential oil via vortexing, ultrasonication, and high shear homogenization. The concentration of EPS (among 0.5, 1, 1.5, and 2 %) and the ratio of EPS to essential oil (among 1:0.5, 1:1, 1:1.5, and 1:2) were initially optimized using vortexing. Ultrasonication and high shear homogenization processes were applied to the vortexed samples and optimized the concentration of EPS and the ratio of EPS to essential oil combinations. The emulsion capacity, emulsion stability, the effect of various processing parameters (temperature and salt), and antimicrobial activity were determined for the emulsions prepared from vortexing, ultrasonication, and high shear homogenization. It was found that emulsion capacity and emulsion stability were better in ultrasonication and high shear homogenization treatment compared to vortexing. When these emulsions were treated with various temperatures and the effect of ionic strengths, the order of emulsion stability was recorded as ultrasonication > high shear homogenization > vortexing. Further, there was significant antimicrobial activity against four tested pathogens, namely Listeria monocytogenes (MTCC 1143), S. aureus (MTCC 1144), E. coli (MTCC 433), and Shewanella putrefaciens (MTCC 8104), but no antimicrobial activity against Salmonella enterica (950) was observed. Parameters such as type of emulsion, turbidity, pH, Fourier transform infrared (FT-IR) analysis, and microscopic analyses were also performed for emulsions. This EPS-based emulsion system can be further explored for functional applications in the field of food and health.