| Popis: |
The main purpose of the research was to develop a bio-based environmentally-friendly antimicrobial packaging paper coating, containing microcapsules with a natural antimicrobial core, and a natural polymer wall. The essential oil of Cymbopogon citratus (citronella oil, lemongrass oil), known for its broad-spectrum antimicrobial activity and uses in food, pharmaceutical, cosmetic and repellent products, was chosen as the active compound. Microcapsules were produced by the complex coacervation process. Two pairs of macromolecular colloids of opposite charges were used for the formation of microcapsule walls: gelatin-carboxymethyl cellulose, and gelatin-gumi arabic. Sodium dodecyl sulphate was optionally used as an emulsifier. Microcapsule walls were cross-linked with glutaraldehyde or hardened with a natural tannin (extracted from chestnut wood) also known for its antimicrobial activity. Microcapsules were characterised by light-transmission and scanning electron microscopies. A container type microcapsules with a distinct liquid core and elastic natural polymer wall were obtained, with diameters 10 to 200 μm. Antimicrobial effects of microencapsulated citronella oil were determined on Bacillus subtilis and Escherichia coli. Freshly prepared aqueous microcapsule suspensions were formulated with or without binders and coated on packaging paper on a laboratory coating device. Mechanical activation of pressure-sensitive microcapsules was achieved by a 3 kg or 5 kg metal weight pulling test. Antimicrobial activity of coated papers with citronella oil coacervation microcapsules was tested by a modified agar plate method in sealed petri dishes, where mechanically activated microcapsules released vapors of citronella oil into the atmosphere of the petri dish, thus affecting the growth of microorganisms. The conclusion is that complex coacervate citronella oil microcapsules can be used for environmentally-friendly antimicrobial coated packaging paper products that require a combined prolonged antimicrobial activity and a quick release of the active substance by mechanical pressure. |
