WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2024 31 (CONTINUED ON PAGE 32) Case study The study was carried out within the research project “ICHTHYS: OptImization of novel value CHains for fish and seafood by developing an integraTed sustainable approacH for improved qualitY, safety and waSte reduction” funded by the EU Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement number 872217 (ICHTHYS) https://www.ichthys-eu.org/about. Research was conducted at the Agricultural University of Athens, in Greece and the University of Modena and Reggio Emilia, in Italy, and aimed to synthesize biodegradable packaging materials based on HPMC and different plasticizers (glycerol, oleic acid, and linoleic acid) to produce suitable flexible packaging for fresh gilthead seabream fillets. The method for HPMC-based film preparation is summarized in Figure 2. The produced films were tested for their physicochemical and mechanical properties and applied on gilthead seabream (Sparus aurata) fillets maintained at 2℃. The produced materials were tested for their surface morphology, bonds between the molecules, water content, water solubility, hydrophobicity, and mechanical, optical, and water barrier properties (Figures 3 and 4). They also were applied on fresh gilthead seabream fillets and the shelf life associated with each film was estimated under refrigerated storage conditions (2℃). Results and Conclusions The visual appearance of the produced films is important, as it affects consumer acceptance (Pirsa and Mohammadi 2021). As is shown in Figure 5, films plasticized with glycerol were more transparent compared to the other tested blends. The surface morphology of the produced films with different plasticizers is also an important parameter, as it allows the understanding of the film surface structure and the arrangements between the different ingredients in the final material. The physicochemical and mechanical properties of the materials are affected by these arrangements. As seen in Figure 6, glycerol creates a uniform matrix with a low percentage of particles while fatty acids had lower compatibility within the HPMC matrix, probably because HPMC is a hydrophilic compound while fatty acids are hydrophobic (Rodrigues Freitas et al. 2016, Deshmukh et al. 2017). The interactions between HPMC and plasticizers were also tested by Fourier-transform infrared (FT-IR) spectroscopy which is suitable for organic and polymeric materials. The results showed that films made from HPMC and glycerol had strong bonds in carbonyl functional group (C-O-C), while films made from HPMC and fatty acids had strong bonds in carboxyl acid groups (-COOH). Regarding mechanical properties and thickness, films plasticized with glycerol had lower thickness, indicating that they were more compact and more flexible. Linoleic acid resulted in lower maximum strength until breakage. Films with oleic acid had the higher value of elongation at breaking, which represents the stiffness of a film, and is acceptable for biodegradable materials for food applications as it increases the capability of film to wrap products. The hydrophobicity or hydrophilicity of a material is determined through water contact angles onto the material surfaces, indicating its ability to resist water absorption (Kchaou et al. 2018). In general, HPMC-based films have low contact angles due to the fact that HPMC has polar functional groups of oxygen, and the molecular interactions are more evident (Athanasopoulou et al. 2024). Films with glycerol were characterized as hydrophilic with a contact angle lower than 90° while films with oleic and linoleic acid were hydrophobic with a contact angle higher than 90°. Hydrophobicity is a desirable property in food packaging materials as it indicates the ability to repel water and other liquids. This ability can aid, to an extent, the shelf life of food products (Asim et al. 2022). The determination of water barriers of food packaging is an important parameter for retaining the quality of food products. Each food product has specific water barrier requirements for the wrapping material to avoid microbial contamination. The HPMC materials in general have high values of water vapor permeability, as they have long hydrophilic chains (Athanasopoulou et al. 2024). For this reason, hydrophobic compounds such as fatty acids are added FIGURE 5. The produced HPMC-based packaging materials. FIGURE 6. Surface morphology of films based on HMPC, with (a) glycerol, (b) oleic acid, and (c) linoleic acid. The surface morphology of the produced films with different plasticizers is also an important parameter, as it allows the understanding of the film surface structure and the arrangements between the different ingredients in the final material.
RkJQdWJsaXNoZXIy MjExNDY=