Characterization of Synthetic Polymer Coated with Biopolymer Layer with Natural Orange Peel Extract Aimed for Food Packaging

Abstract

This research was aimed to make biolayer coatings enriched with orange peel essential oil (OPEO) on synthetic laminate, oriented poly(ethylene-terephthalate)/polypropylene (PET-O/PP). Coating materials were taken from biobased and renewable waste sources, and the developed formulation was targeted for food packaging. The developed materials were characterized for their barrier (O₂, CO₂, and water vapour), optical (colour, opacity), surface (inventory of peaks by FTIR), and antimicrobial activity. Furthermore, the overall migration from a base layer (PET-O/PP) in an acetic acid (3% HAc) and ethanol aqueous solution (20% EtOH) were measured. The antimicrobial activity of chitosan (Chi)-coated films was assessed against Escherichia coli. Permeation of the uncoated samples (base layer, PET-O/PP) increased with the temperature increase (from 20 °C to 40 °C and 60 °C). Films with Chi-coatings were a better barrier to gases than the control (PET-O/PP) measured at 20 °C. The addition of 1% (w/v) OPEO to the Chi-coating layer showed a permeance decrease of 67% for CO₂ and 48% for O₂. The overall migrations from PET-O/PP in 3% HAc and 20% EtOH were 1.8 and 2.3 mg/dm², respectively. Analysis of spectral bands did not indicate any surface structural changes after exposure to food simulants. Water vapour transmission rate values were increased for Chi-coated samples compared to the control. The total colour difference showed a slight colour change for all coated samples (ΔE > 2). No significant changes in light transmission at 600 nm for samples containing 1% and 2% OLEO were observed. The addition of 4% (w/v) OPEO was not enough to obtain a bacteriostatic effect, so future research is needed.

Keywords: chitosan biolayer; gas and water vapor barrier; orange peel essential oil; overall migration.

Figure 1

Permeance (q) values through PET-O/PP (12/50 µm) referent commercial sample at different temperatures.

Figure 2

The overall migration values from PET-O/PP referent commercial sample into food simulants: 3% (w/v) acetic acid (HAc) and 20% v/v aqueous ethanol (EtOH).

Figure 3

FTIR spectra of PET-O/PP (referent commercial sample; facing the PP side of the laminate) before and after exposure to food simulants.

Figure 4

Pictures of films taken on the white surface.

Figure 5

Absorbance (A) values for plain PET-O/PP referent commercial sample and the Chi-coatings enriched with orange peel essential oil (OPEO): 1% w/v (A), 2% w/v (B), and 4% w/v (C).

Figure 6

Effect of the PET-O/PP film coated with chitosan enriched with 4% OPEO on the growth of Escherichia coli (ATTC 25922). (a) Orange peel essential oil (OPEO), 100 µL, and (b) PET-O/PP referent commercial sample with Chi-coating enriched with 4% OPEO (C/OPEO).

Figure 6

Effect of the PET-O/PP film coated with chitosan enriched with 4% OPEO on the growth of Escherichia coli (ATTC 25922). (a) Orange peel essential oil (OPEO), 100 µL, and (b) PET-O/PP referent commercial sample with Chi-coating enriched with 4% OPEO (C/OPEO).