Development and characterization of biobased food packaging materials from orange and pomegranate peel waste

Environmentally friendly, renewable and sustainable packaging materials are of getting interests as an alternative to the petroleum-based polymers and there has been more focus on bio-based materials from different sustainable sources including food waste. The aim of this study was to develop biobased films from pomegranate and orange peels. For this purpose, pomegranate and orange peels were dried and processed into flour in four different particle sizes. The effects of particle size, citric acid (3% and 5%) and glycerol (7% and 10%) concentrations on the physical and mechanical properties of bio-based films produced by solvent casting method were investigated. Considering the mechanical properties, the effect of particle size on antimicrobial, antioxidant, light transmission, morphological and thermal properties was investigated for films containing 5% acid and 7% glycerol. Results showed that the particle size was the most important parameter (p≤0,05) on the mechanical properties of the films tested as reducing the particle size improved the mechanical properties. The mechanical properties (tensile strenght and elongation at break) were improved by using 5% acid concentration for the pomegranate and orange peel based films. Increasing glycerol concentration resulted in significant decrease in tensile strength values at all particle sizes for each waste type. However, elongation at break value (40.29%) was the highest at smallest particle size of 53 micron and 5% acid concentration for the pomegranate peel films. Pomegranate and orange peel based films showed very high antimicrobial and antioxidant activity against E.coli and S. aureus. SEM images showed that both pomegranate and orange peel based films had a homogeneous, smooth and crack-free surfaces. The results of TGA-DSC analysis for pomegranate film showed that glass transition, melting and crystallinity temperatures were 90-100 ℃, 200-220 ℃ and 250-255 ℃, respectively. For orange peel based films, the glass transition, melting and crystallinity temperatures were 85-90 ℃, 200-220 ℃ and 255-260 ℃, respectively. In conclusion, pomegranate and orange peels could be good potential as antimicrobial and antioxidant sources to be used in the polymer matrix in the sustainable and active food packaging, but especially mechanical and thermal properties need further improvement. Keywords: Biodegradable plastic, food packaging, pomegranate peel, orange peel, food waste, biopolymer