Abstract
In this study, some properties and antioxidant capacity of anchovy (Engraulis encrasicholus) by-product protein films with added 0.5, 1.0 and 1.5% of thyme essential oil were investigated. The films with thyme essential oil had higher elongation at break, water vapour permeability and oxygen permeability, lower solubility and tensile strength than control film (p<0.05). The incorporation of thyme essential oil affected transparency values of the films, but only the addition of 1.5% of thyme essential oil significantly reduced the transparency (p<0.05). In the film matrix, molecular organisation and intermolecular interaction were changed by thyme essential oil addition. The films with thyme essential oil had a heterogeneous surface and a relatively smooth cross-section structure. Slightly higher phase transition and lower glass transition temperatures were observed in films with thyme essential oil. The antioxidant capacity of the films was improved by incorporating thyme essential oil depending on its volume fraction.
Highlights
Due to the environmental impact of the excessive quantity of non-degradable waste materials, packaging studies have recently focused on developing biodegradable and/or edible packaging films obtained from natural sources, such as by-products of agriculture, fishing or livestock raising (1)
Various properties of chitosan films containing thyme essential oil were investigated by Altiok et al (12), and they indicated that oxygen transmission and Water vapour permeability (WVP) rate of the film barely increased, while its mechanical properties decreased with the addition of thyme essential oil
Similar results were found by Arfat et al (9) for fish protein isolate/fish skin gelatin films with zinc oxide nanoparticles and basil leaf essential oil, where amide I, amide II and amide III peaks were observed at ν=1631, 1537 and 1238 cm–1, respectively
Summary
Due to the environmental impact of the excessive quantity of non-degradable waste materials, packaging studies have recently focused on developing biodegradable and/or edible packaging films obtained from natural sources, such as by-products of agriculture, fishing or livestock raising (1) Among these natural sources, proteins from fish processing by-products have been successfully utilised in the development of edible films, as reported by various researchers (2–4). Kavoosi et al (13) found that the addition of thyme essential oil to gelatin films led to an important decrease in tensile strength (TS), an increase in water solubility, elongation at break (EAB) and WVP They indicated that the films containing thyme essential oil showed perfect antioxidant properties. Jouki et al (14) found that thyme essential oil addition to quince seed mucilage films increased the WVP and oxygen permeability (OP), whereas decreased the glass transition temperature
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