The effect of polyethylene crystallinity and polarity on thermal stability and controlled release of essential oils in antimicrobial films

Abstract

Antimicrobial packaging can preserve and increase shelf life of free preservatives food products. Active materials present in the packaging material can migrate, in a controlled manner, to the food surface, avoiding bacterial and fungal proliferation and keeping the food product edible for longer periods of time. Essential oils (EO) are natural antimicrobial agents that can be released to the headspace with no direct contact between the package and the food. To minimize loses of EO during high heat melt processing, a three stages process was implemented and tested. Antimicrobial films were prepared by melt mixing a variety of polyethylene copolymers in the presence of organo-modified montmorillonite nano clay (NC) and thymol, an EO present in oregano and thyme. A controlled EO desorption from films can be achieved by changing the polymer crystallinity and polarity. As the crystallinity increased, the thermal stability of the EO during the extrusion process improved. The addition of NC affects the structure and homogeneity of the crystals. The combination of high polymer crystallinity and chemical affinity between EO and NC increased the thermal stability of the EO during film processing, enabling to control the desorption rate. The effect of multilayer structure based on varied densities and polarities was also studied. Increasing the polarity of the outer layers in multilayered film reduced the EO desorption rate as a result of chemical interactions between the polymer and the EO. The final antimicrobial activity of the films was also found to be dependent on the EO partitioning.

Preparation of halloysite nanotubes coated with Eudragit for a controlled release of thyme essential oil

“…This clay had a specific gravity of 2.53 g/cm 3 and a pore volume of 1.26-1.34 mL/g. TO was purchased from Dotter-Line (Gunpo, Korea).…”

“…Accurately weighed quantities of sample (300 mg) were incubated at 258C oven. At specific time intervals (0, 1.5, 3,6,12,24,36,48,72, and 96 h), each sample was added to 10 mL of absolute ethyl alcohol to determine the amount of TO remaining after evaporation. The amount of TO was measured using the method described above.…”

Antibacterial and antifungal LDPE films for active packaging

“…[47][48][49] The prevailing methodology in most studies is to incorporate organo-modified montmorillonite clays (MMT) as filler during melt compounding. [26,31,50] The rational for the incorporation of the clay was to improve the barrier properties of the films in order to protect the volatile and heat-sensitive essential oil molecules.…”

Effect of clay and clay/essential oil in packaging films

“…Carrier systems for these oils are constantly being proposed as alternatives due to their antimicrobial and antioxidant properties . Although some recent studies report the use of EOs with organic antimicrobial characteristics as additives for the development of antimicrobial packaging , efforts still need to be made to extend and control the time of bacterial action, besides improving thermal stability, since the antibacterial activity is not lost during processing by extrusion.…”