Fabrication and Characterization of Active Poly(Lactic Acid) Films Containing Thymus daenensis Essential Oil/Beta-cyclodextrin Inclusion Complex and Silver Nanoparticles to Extend the Shelf Life of Ground Beef

Thymus daenensis Celak. (T. daenensis) essential oil (TDO) was encapsulated into beta-cyclodextrin (ss-CD) by co-precipitation method and incorporated into polylactic acid (PLA) films along with silver nanoparticles (AgNPs) to generate the active PLA film for extending the ground beef shelf life at 4 degrees C. Scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FTIR) confirmed the proper dispersion of AgNPs, TDO, and ss-CD/TDO throughout the PLA films. Different physical properties were observed in the active PLA films, so that the addition of ss-CD/TDO in the films increased the thickness and decreased the tensile strength (TS) and elongation at break compared to TDO films. The color of the AgNP films was lightly darker than the others. The microbial evaluation of the packaged ground beef samples with active PLA films indicated that accompanying AgNPs with ss-CD/TDO and TDO could synergistically inhibit total viable bacteria counts, psychrotrophic bacteria counts, and Enterobacteriaceae counts during the sample's storage for 12 days. This effectiveness was also observed in controlling changes in pH and total volatile basic nitrogen (TVB-N) in the samples. Considering the efficient entrapment of TDO in ss-CD, the shelf life of samples was significantly extended, due to sustained and long-lasting release of the essential oil compounds, compared to the net TDO films. Based on the results, it can be concluded that ss-CD/TDO+AgNP film can be a promising approach to extend the shelf life of ground beef.

Automated summary

Encapsulation of Thymus daenensis essential oil with beta-cyclodextrin and incorporation of silver nanoparticles into polylactic acid films can extend the shelf life of ground beef and inhibit microbial growth.