Investigation of the use of menthol and organic acid based deep eutectic solutions as plasticizers in food packaging

The environmental pollution has became a major crisis as the human population grows almost exponantially and petrol-derived plastics are the most frequent pollutant of this global crisis. So the substitution with biodegredable materials is a promising solution for pollution of the planet earth. However the biodegradable packaging materials lacks of some essentials, especially mechanical resistance. Although plasticisers are added to biodegradable polymers to improve its mechanical properties, most of the common ones are toxic. Therefore coherent biodegradable plasticisers are needed to be researched. Deep eutectic solvents (DES) which are classified as "generally recognized as safe (GRAS)", are promising alternative plasticiser. In the current thesis, menthol (M) and organic acid (levulinic acid (Lev) and pyruvic acid (Pyr)) based DES are examined as plasticiser. Both DES (M-Lev and M-Pyr) are added to casted polylactic acid (PLA) films with the mass concentration of 5%, 10%, and 20%. Performance of these organic plasticisers are compared with two most commonly used plasticiser in the packaging industry, di-2-ethylhexyl phthalate (DEHP) and epoxidized soybean oil (ESBO). Optical, mechanical, barrier and structural properties of DES containing PLA films were examined. Characteristic Fourier Transform Infra-Red (FTIR) absorbance peaks of menthol and the organic acids are confirmed by the FTIR spectrum of the DES. Densities which are important in terms of processability were measued as similar with the comperates. Additionally, flow behavior of the DES were found to be Newtonian. DES which are hypothesized as to improve mechanical properties of the PLA are found as comperable with ESBO and DEHP. Moreover, optical properties were similar of DES containing films with the ESBO and DEHP containing ones. While water solubility and water retention were greater for the DES containing films, migration were lower especially to the fatty foods which limits the use of ESBO and DEHP are easily migrating to the fatty foods. In conclusion both DES are compatible with PLA. Use of DES as plasticiser has improved mechanical and barrier properties of the films. When the findings of the film analysis were considered it was suggested to add M-Lev and M-Pyr with a concentration of 10% and 5% respectively.