LAYER-BY-LAYER ASSEMBLY OF POLYLACTIC ACID AND CHITOSAN FILMS DOPED WITH OLIVE LEAF EXTRACT AND DEEP EUTECTIC SOLVENTS FOR EXTENSION OF SHELF LIFE OF CHEESE PRODUCTS

Date

2026-8-14

Author

Ahmadova, Nazrin

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Active food-packaging films were developed by sequentially depositing olive leaf extract (OLE)-containing chitosan layers onto a poly(lactic acid) (PLA) substrate using a doctor-blade applicator. The films were designated PLA/CH0, PLA/CH1, PLA/CH2, and PLA/CH4 according to the number of deposited layers. A deep eutectic solvent (DES) incorporated into the coating formulation acted as a plasticizer and enabled direct deposition of the hydrophilic chitosan-based coating onto the hydrophobic PLA substrate without prior surface treatment or an intermediate layer. Film thickness increased progressively from 16.3 to 41.3 µm, confirming successive build-up, while FTIR indicated no detectable chemical alteration of the PLA backbone. Increasing the number of layers reduced tensile strength by approximately 62% and increased water vapor permeability by approximately 121%, whereas total phenolic content increased from 11.97 to 342.74 mg GAE/g film, accompanied by higher DPPH, ABTS, and FRAP antioxidant capacities and film opacity. Agar-contact assays demonstrated contact-mediated antifungal and microorganism-dependent antibacterial activity. PLA/CH4 was further evaluated using Cheddar cheese stored at 4 °C for 42 days. On day 14, the total viable count and yeast and mold count were 4.13 and 3.82 log CFU/g, compared with 6.25 and 5.78 log CFU/g for PLA/CH0. PLA/CH4 also limited the storage associated pH increase and maintained significantly lower TBARS values from day 7 to day 42, with an approximately 85% reduction on day 14. These findings demonstrate that the OLE-containing chitosan coating imparted antioxidant, antimicrobial, and food-preservation functionality to PLA, although increasing the number of layers involved a trade-off with tensile strength and barrier performance.

Subject Keywords

Olive Leaf Extract; Chitosan; Polylactic Acid; Deep Eutectic Solvent; Active Packaging

URI

https://hdl.handle.net/11511/120079

Collections

Graduate School of Natural and Applied Sciences, Thesis