The impacts of chitosan-essential oil nanoemulsions on the microbial diversity and chemical composition of refrigerated minced meat.

Essential oils of Mentha piperita, Punica granatum, Thymus vulgaris and Citrus limon in olive oil as a carrier were mixed with biopolymer chitosan to prepare nanoemulsions. The formulations were prepared using the following ratios: 0.5:0.5:4, 1:1:4, and 2:3:4 of chitosan: essential oil: olive oil, respectively, representing 12 formulations based on four essential oils. Based on the characterization of nanoemulsions, M. piperita, T. vulgaris, and C. limon oils produced the smallest droplets. However, P. granatum oil produced high droplets size. The products were evaluated in vitro for antimicrobial activity against two pathogenic food bacteria, Escherichia coli and Salmonella typhimunium. The in vivo antibacterial activity was further investigated on minced beef meat during storage at 4 °C for ten days. Based on the MIC values, E. coli was more susceptible than S. typhimunium. Chitosan was more effective as an antibacterial than essential oils (MIC = 500 and 650 mg/L against E. coli and S. typhimunium). Among the tested products, C. limon had a more antibacterial effect. In vivo studies proved that C. limon and its nanoemulsion were the most active products against E.coli. These results suggest that chitosan-essential oil nanoemulsions may help extend the shelf life of meat by acting as antimicrobial agents.

Facile synthesis and characterizations of antibacterial and antioxidant of chitosan monoterpene nanoparticles and their applications in preserving minced meat.

Chitosan nanoparticles loaded monoterpenes (ChMNPs) were prepared for preservation of minced meat from oxidative changes and growth of microorganisms. Four monoterpenes (limonene, linalool, menthol and thymol) were used to synthesis of four different types of ChMNPs. The physicochemical characteristics of nanoparticles were analyzed using Scanning electron microscopy (SEM) and Zeta potential. SEM showed that the nanoparticles were nearly uniformly shape and size and the zeta potential values ranged between 0.0346 and -0.1690 mV. In vitro antimicrobial activity of Ch, monoterpenes (M) and ChMNPs against Gram (-) bacteria Escherichia coli (ATCC 8739) and Salmonella typhimurium (ATCC 1402) was analyzed using serial dilution test. E. coli was more susceptible than S. typhimurium to these products. ChMNPs exhibited good in vivo antimicrobial and antioxidant property for the minced meat samples during refrigerated storage. Verification of testing hypothesis was performed by assessing a DPPH radical scavenging activity, peroxide value and E. coli reduction of experimental nanoparticles. Significant effects of ChMNPs were observed at 1000 and 2500 mg/kg on the total number of E. coli in meat samples during storage time. The results indicate that ChMNPs can be used to preserve food as antimicrobial agents and to extend shelf life.