Development and Evaluation of a Novel-Thymol@Natural-Zeolite/Low-Density-Polyethylene Active Packaging Film: Applications for Pork Fillets Preservation

Abstract

Sustainability, the circular economy, and the “greenhouse” effect have led the food packaging industry to use naturally available bio-compounds. The integration of such compounds in packaging films increases food safety and extends food shelf-life. The development of an active/antioxidant packaging film based on the widely commercially used low-density polyethylene, natural zeolite, and Thymol, a natural extract from thyme oil, is presented in this work. The obtained active films were characterized using X-Ray Diffraction, Fourier-Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Differential Scanning Calorimetry techniques. The tensile strength, water–oxygen barrier properties, and total antioxidant activity were measured. Low-density polyethylene incorporated with Thymol@Natural Zeolite at a proportion of 15 wt% was the most promising material and was used as film to wrap-up pork fillets. The thiobarbituric acid (TBA) method and heme iron measurements indicated a delayed lipids oxidation using this film. A linear correlation between the TBA method and heme iron values seems to be established, which could result in a fast method to determine the degree of lipid oxidation in pork fillets. Finally, a two-stage diffusion process during Thymol release was observed, and the values of the diffusion coefficient was 2.09 × 10−7 and 1.21 × 10−8 cm2/s for each stage. The applied pseudo-second sorption model provided a rate constant k2 = 0.01647 (s−1). These results indicate the strong potential of such films to be used as food packaging materials free of E-number preservatives.

Thymol@activated Carbon Nanohybrid for Low-Density Polyethylene-Based Active Packaging Films for Pork Fillets’ Shelf-Life Extension

“…In Figure 3c, the % mass loss of the first step and the % total mass loss are calculated by subtracting the mass values of TO@AC from the mass values of pure AC at 300 • C and 500 • C, respectively. The total TO mass adsorbed was found to be equal to 50.7 wt%-a value considerably higher than those recently obtained for TO's adsorption on natural zeolite (35.5 wt%) [41] and HNTs (31.4 wt%) [40]. This outcome reveals that AC is a promising bio-based material for application as a nanocarrier in controlled-release applications within the active food packaging sector.…”

“…This step correlates with the decomposition of cellulose, lignin, and hemicellulose matter, along with the expulsion of volatile matter that occurs during the carbonization process [59]. The TG plot of the TO@AC nanohybrid (see line (2) in Figure 4c) displays a first mass-loss step below 300 • C and a second one beginning at around 350-400 • C and ending around 500 • C. This pattern suggests that a fraction of TO desorbs from the AC surface in the temperature range from 150 to 300 • C, while another TO fraction desorbs in a higher temperature range from 350 to 500 • C. Considering the previously studied textural features of the AC [42], the Brunauer-Emmett-Teller surface area (S gBET ) of the AC was 1372 m 2 /g, with the micropore volume being 84.6% and exhibiting micropores at D micro1 = 1.28 and D micro2 = 1.6 nm [41]. Given that the size of a TO molecule is roughly equal to that of a phenol molecule (about 0.6-0.8 nm), a fraction of TO could be adsorbed within the micropore structure of AC.…”

“…This transformation was achieved by operating a hydraulic press with heated platens at 110 °Cand a constant pressure of 2 MPa for 2 min [12,43]. The methods used to carry out the physicochemical characterization of AC, TO@AC powders, and LDPE/AC and LDPE/TO@AC films were as described in [38][39][40][41]. To study possible crystallinity changes in the AC during the process of TO@AC nanohybrid development, XRD analyses were performed on both pure AC and TO@AC.…”

“…Palate cleansers-room-temperature distilled water and unsalted crackers-were The thiobarbituric-acid-reactive substances (TBARS) values of the packed pork fillets after 2, 4, 6, 8, 10, and 12 days were determined using the method of Tarladgis et al [50], as recently modified by Karabagias et al [51]. The methodology for determination of the TBARS values of packaged fresh pork fillets was as described in detail recently [40,41].…”

Active packaging from natural ingredients applied to meat: A review

“…The use of natural herbal ingredients in conjunction other preservatives can increase the effectiveness and minimize the influence on the organoleptic characteristics of meat [35]. The addition of natural extract ingredients that have antioxidant content in packaging materials can protect food from lipid oxidation and can extend its shelf life [36].…”