Synergistic Antimicrobial Activities of Limonene with Mineral Carriers in LDPE Films for Active Packaging Application

Abstract

The integration of essential oils (EOs) into polymers to endow antimicrobial properties has received a lot of attention. EOs are remarkable in that they have broad antimicrobial activity from a natural source while also being volatile. Their volatility, on the other hand, makes high-temperature processing techniques difficult to incorporate into polymers. In this study, active films based on low-density polyethylene (LDPE) and limonene essential oil (LEO) were prepared and characterized. Before incorporation of LEO into LDPE, vacuum pulling method was used to load the LEO into five different mineral carriers. All Carrier-LEO complexes were added into LDPE using melt compounding. The goal is to analyze the potential use of these formulations to achieve prolonged antimicrobial film packaging. The halloysite nanotubes (HNTs), kaolinite (Kao), mesoporous silica nanoparticles (MSNs), zinc oxide nanoparticles (ZnONPs), and molecular sieve type 4A (Z4A) were used as mineral carriers for limonene. The functional characterizations including mechanical, thermal, optical, barrier, and antimicrobial properties as well as limonene release behavior from the LDPE composite films were investigated. As expected, free limonene molecules acted as a plasticizer in the LDPE matrix. Thermogravimetric analysis (TGA) showed 20-25% of the initial limonene content was retained against thermal degradation in compounding and film making steps and its release from the films was efficiently delayed. A decrease in optical and oxygen barrier properties, as well as elastic modulus and tensile strength, was obtained for all developed films compared with neat LDPE. Significant antibacterial activities of the films were observed against Escherichia coli DH5-Alpha (E. coli) as a model gram-negative bacterial species. Moreover, the obtained results and the short-term and long-term release studies indicated that both HNTs and the MSNs due to their strong synergistic interactions with limonene exhibited sustained release profiles of limonene from LDPE films. Thus, these new active polymer composites present promising features in controlling microbial contamination, rendering them as excellent candidates in active packaging applications.

Development, Characterization, and Evaluation as Food Active Packaging of Low-Density-Polyethylene-Based Films Incorporated with Rich in Thymol Halloysite Nanohybrid for Fresh “Scaloppini” Type Pork Meat Fillets Preservation

“…The obtained TO@HNT nanohybrids were loaded in LDPE via a melt-extrusion preparation process at 5, 10, and 15 %wt. nominal contents, which were higher compared to those reported in the literature [ 15 , 16 , 17 , 18 , 19 ]. Such high contents of HNT and/or TO@HNT nanofillers, to the best of our knowledge, are reported for the first time.…”

“…essential oils concentration that exhibited a higher inhibitory effect than the films obtained using the ionizing treatment. Recently, researchers proposed adsorption of EOs in nanoclays, such as montmorillonite (Mt) and Halloysite nanotubes (HNT), to develop a hybrid EO/nanoclay nanostructure and incorporation of such hybrids into the LDPE matrix [ 15 , 16 , 17 , 18 , 19 ]. Nanoclays such as HNT act as nanoreinforcements, barrier agents, and EOs nanocarriers according to this method.…”

“…Nanoclays such as HNT act as nanoreinforcements, barrier agents, and EOs nanocarriers according to this method. Mahdi et al [ 17 ] performed impregnation under vacuum to load limonene into five different mineral nanocarriers, i.e., HNT, kaolinite, mesoporous silica nanoparticles, zinc oxide nanoparticles, and molecular sieve type 4A. The obtained limonene–nanocarrier hybrids were incorporated into LDPE and short- and long-term release studies indicated that both HNT and mesoporous silica nanoparticles exhibited long-time release profiles of limonene from LDPE films.…”

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

“…Hypothesis tests were carried out via the ANOVA method, using the Tukey criteria for equal-variance assumptions, setting confidence intervals at 95% and significance levels at p < 0.05. In addition, the assurance of mean equality (EA%) or inequality (IA%) was examined based on empirical equations previously reported in the literature [ 55 ]. Across all tests, it was observed that the mean values of the various sample properties that were statistically different exhibited an inequality assurance factor (IA%) of over 56%, while the mean values that were statistically equal exhibited an equality assurance factor (EA%) of over 61%.…”

Effect of Corona Treatment Method to Carvacrol Nanocoating Process for Carvacrol/Halloysite-Nanotube/Low-Density-Polyethylene Active Packaging Films Development

“…In the literature there is a plethora of studies with EOs addition on polymers such as polyethylene (PE), low density polyethylene [7][8][9], polyethylene tetraphthalate (PET) [10], polystyrene (PS) [11] and biopolymers such as starch, chitosan, gelatin, alginates, poly-lactide acid (PLA) active packaging films [12][13][14][15][16][17][18][19][20]. In addition, there are many studies with use of EOs active components in active packaging systems such as limonene, eugenol, thymol, cinnamaldehyde and carvacrol [21][22][23][24][25][26][27][28]. Carvacrol (CV) is a phenolic monoterpenoid found in EOs of oregano (Origanum vulgare), thyme (Thymus vulgaris), pepperwort (Lepidium flavum), wild bergamot (Citrus aurantium bergamia), and other plants and is useful for its significant antibacterial, antifungal, antimicrobial, and antioxidant activities.…”