Articles
Effect of shellac coating on the properties of egg white protein (EWP) films for cherry tomato packaging
Article number
1396_50
Pages
375 – 384
Language
English
Abstract
Egg white protein (EWP) films have limited applications for the modified atmosphere packaging (MAP) of fresh fruits and vegetables due to their poor water vapour barrier properties compared to commonly used petroleum-based polymers.
There are some strategies to improve this drawback such as nanoparticles addition, layer intercalation, or coatings application.
Shellac is a natural non-toxic polymer with good film-forming properties, biodegradability, and noted moisture resistance.
For these reasons, in this study shellac was used as coating material for EWP films obtained by compression moulding and was applied in two thicknesses (24 and 40 µm) on one or both sides of the film.
The objective was to improve the barrier properties of these films and bring them closer to those of bio-based commercial films such as polylactic acid (PLA), and to compare with petroleum-based materials such as oriented polypropylene (OPP). At 23°C, the oxygen transmission rate (OTR) of EWP films was lower than that of PLA and OPP films, while the water vapour transmission rate (WVTR) was significantly higher.
Shellac coating reduced the WVTR of EWP films up to values close to those of PLA and did not change OTR at 50% relative humidity.
The colour of coated EWP films differs from that of commercial films, especially in lightness and in yellowish tone, which decreased and increased, respectively, with the thickness and number of coating layers.
Cherry tomatoes were kept for 21 days at 4°C in bags made with these films to verify with real-product situations these improvements.
The product experienced a similar weight loss in shellac-coated EWP packages compared with that of PLA, so in this regard it could be considered an alternative to this commercial film.
However, further improvement needs to be addressed in order to make them comparable to water barrier properties of OPP.
There are some strategies to improve this drawback such as nanoparticles addition, layer intercalation, or coatings application.
Shellac is a natural non-toxic polymer with good film-forming properties, biodegradability, and noted moisture resistance.
For these reasons, in this study shellac was used as coating material for EWP films obtained by compression moulding and was applied in two thicknesses (24 and 40 µm) on one or both sides of the film.
The objective was to improve the barrier properties of these films and bring them closer to those of bio-based commercial films such as polylactic acid (PLA), and to compare with petroleum-based materials such as oriented polypropylene (OPP). At 23°C, the oxygen transmission rate (OTR) of EWP films was lower than that of PLA and OPP films, while the water vapour transmission rate (WVTR) was significantly higher.
Shellac coating reduced the WVTR of EWP films up to values close to those of PLA and did not change OTR at 50% relative humidity.
The colour of coated EWP films differs from that of commercial films, especially in lightness and in yellowish tone, which decreased and increased, respectively, with the thickness and number of coating layers.
Cherry tomatoes were kept for 21 days at 4°C in bags made with these films to verify with real-product situations these improvements.
The product experienced a similar weight loss in shellac-coated EWP packages compared with that of PLA, so in this regard it could be considered an alternative to this commercial film.
However, further improvement needs to be addressed in order to make them comparable to water barrier properties of OPP.
Authors
V. Baquero, M.L. Salvador, J. González-Buesa
Keywords
edible film, egg white protein, shellac, compression moulding, food packaging, modified atmosphere, quality
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