| Natural essential oil extracted from plant has characteristic odor, which is natural, safe, nontoxic and has good control against food spoilage microorganism. Natural essential oil has been studied extensively as most potential substitute of traditional chemical preservative. Application of natural essential in food industrial is limited by its volatile and hydrophobic nature, which could be solved by microcapsule technology. This paper mainly researched preparation, characterization and antibacterial properties of cinnamon essential oil (CEO) microcapsules made by complex coacervation and layer by layer assembly (LBL) technology. Sustained release of complex coacervation CEO microcapsules was studied by comparison to CEO microemulsion. Significance of this study is to develop natural biological preservatives and speed up the step of substitution of traditional chemical preservatives and build theory basis for the use of plant essential oil in food industry.Firstly, nano-capsule were fabricated by complex coacervation process, taking chitosan as wall material and CEO as core material. Then effect of core material concentration on the microcapsule size, zeta potential and encapsulation efficiency were studied. The dynamic bacteriostatic curve of different core material concentration was plotted by measuring the bacteriostatic effect on Escherichia coli and Staphylococcus aureus with varied core material concentration. Result indicated that core material concentration had no significant effect on the microcapsule size but can distinctly affected the zeta potential, effect on the encapsulation efficiency has no obvious regularity. Bacteriostatic effect of cinnamon essential oil nano-capsule increases with increase of core material concentration, while the bacteriostatic effect of CEO nano-capsule on Escherichia coli is better than that of Staphylococcus aureus.Secondly, Bacteriostatic effect of CEO in different form were observed by comparing the bacteriostatic effect of CEO pure aqueous solution, CEO microemulsion and CEO microcapsules after placing different time. Result indicated that antibacterial endurance of CEO nano-capsule was the best and that of pure aqueous solution was the worst while CEO microemulsion was in the middle.Finally, effects of LBL CEO microcapsules on food spoilage microorganism and preparation of LBL CEO microcapsules were under investigation. LBL CEO microcapsule were prepared with chitosan and sodium lignosulfonate as wall material by LBL technology. Effects of assembly time, ploy-electrolyte concentration, pH and ionic strength on zeta potential of LBL microcapsules were studied. Inhibition of LBL microcapsules with different layers in vitro and in vivo against food spoilage microorganism were observed. Results indicate that the assembly time, polyelectrolyte concentration, pH and ionic strength all have significant influence on the surface zeta potential of microcapsule. Results of in vitro bacteriostasis experiment indicated that assembly layer has positive impact on the bacteriostatic effect and endurance of LBL microcapsules, bacteriostatic effect of CEO microcapsule of different layers on mould was better than that of bacteria. Results of antibacterial experiment in vivo indicated that assembly layer number and outside layer had significant impact on inhibiting effect against fruit postharvest pathogens. |
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