Biofilm Formation Reduction by Eugenol and Thymol on Biodegradable Food Packaging Material

Recent Advances in Biofilm Control Technologies for the Food Industry

Biofilms remain a major challenge in the food industry due to the increased resistance of foodborne pathogens to antimicrobial agents and food processing stresses, leading to food contamination and significant health risks. Their resistance to preservation techniques, antimicrobial treatments, and processing conditions increases concerns regarding food safety. This review discusses recent developments in physical, chemical, and surface modification strategies to control and remove biofilms in food processing environments. Physical methods, such as thermal treatments, electric fields, and ultrasonic systems, have demonstrated their efficacy in disrupting biofilm structure and improving disinfection processes. Chemical treatments, including the use of sanitizers, disinfectants, acidulants, and enzymes, provide targeted approaches to degrade biofilm matrices and inhibit bacterial adhesion. Furthermore, surface modifications of food contact materials provide innovative solutions for preventing biofilm formation and enhancing food safety. These cutting-edge strategies not only improve food safety but also reduce contamination risk in food processing facilities. The review highlights the mechanisms, efficacy, and applicability of these techniques, emphasizing their potential to mitigate biofilm-associated risks and ensure food quality and safety.

Development of active films with thymol-based hydrophobic eutectic solvents

Thymol, known for its antimicrobial properties, was combined with acetic acid, betaine, and caprylic acid to form hydrophobic natural eutectic solvents (NAES), whose influence on the properties of bovine gelatin films was investigated. Films showed enhanced mechanical performance and a clear plasticizing effect provided by the natural eutectic solvents. At 300 wt% concentration, tensile strength and elongation at break reached 871 ± 78 kPa and 141 ± 10 % for acetic acid, 391 ± 41 kPa and 159 ± 10 % for betaine, and 1209 ± 52 kPa and 198 ± 15 % for caprylic acid. Water vapor permeability and total soluble matter were reduced, and swelling decreased to ~250 %, ~150 %, and ~ 200 % for films with 300 wt% of acetic acid, betaine, and caprylic acid, respectively. Pure thymol exhibited significant volatility, with 17.10 ± 1.50 % weight loss over one week, while the NADES demonstrated dramatically reduced losses (up to 1.15 ± 0.04 %). The films displayed exceptional antibacterial activity, achieving inhibition diameters of 34 mm against Gram-positive and Gram-negative bacteria, and films with caprylic or acetic NAES achieved undetectable CFU levels for major pathogens on chicken breast. These results highlight the antimicrobial potency and enhanced stability of NAES-based gelatin films for active packaging applications.

Extension of shelf life of tomato (Solanum lycopersicum L.) by using a coating of polyhydroxybutyrate-carboxymethyl cellulose-pectin-thymol conjugate

This study targets explicitly finding an alternative to petroleum-based plastic films that burden the environment, which is a high priority. Hence, polymeric films were prepared with carboxymethyl cellulose (CMC) (4%), pectin (2%), and polyhydroxybutyrate (PHB) (0.5%) with different concentrations of thymol (0.3%, 0.9%, 1.8%, 3%, and 5%) and glycerol as a plasticizer by solution casting technique. The prepared films were tested for mechanical, optical, antimicrobial, and antioxidant properties. Film F5 (CMC + P + PHB + 0.9%thymol) showed an excellent tensile strength of 15 MPa, Young's modulus of 395 MPa, antioxidant activity (AA) (92%), rapid soil biodegradation (21 days), and strong antimicrobial activity against bacterial and fungal cultures such as Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus. The thymol content increase in films F6 (1.8%), F7 (3%), and F8 (5%) displayed a decrease in mechanical properties due to thymol's hydrophobicity. For shelf life studies on tomatoes, F2, a film without thymol (poor antimicrobial and antioxidant activities), F5 (film with superior mechanical, optical, antimicrobial, and antioxidant properties), and F7 (film with low mechanical properties) were selected. Film F5 coatings on tomato fruit enhanced the shelf life of up to 15 days by preventing weight loss, preserving firmness, and delaying changes in biochemical constituents like lycopene, phenols, and AA. Based on the mechanical, optical, antimicrobial, antioxidant, and shelf life results, the film F5 is suitable for active food packaging and preservation. PRACTICAL APPLICATION: The developed active biodegradable composite can be utilized as a coating to extend the shelf life of fruits and vegetables. These coatings are easy to produce and apply, offering a sustainable solution to reduce food waste. On an industrial scale, they can be applied to food products, ensuring longer freshness without any technical challenges.

Poloxamer-Based Mixed Micelles Loaded with Thymol or Eugenol for Topical Applications

Poloxamers (P184, P188, and P407) have been investigated as the carrier system for eugenol or thymol. A synergic effect of mixed Poloxamers was proved by enhanced micellar parameters, with a lower critical micelle concentration (about 0.06 mM) and the highest surface adsorption of 9 × 10-7 mol m-2 for P188/P407. Dynamic light scattering revealed a decrease in micellar size after loading with biomolecules. Three mathematical models were applied to study the release kinetics, of which Korsmeyer-Peppas was the best fitted model. Higher relative release was observed for Poloxamer/eugenol samples, up to a value of 0.8. Poloxamer micelles with thymol were highly influential in bacterial reduction. Single P407/eugenol micelles proved to be bacteriostatic for up to 6 h for S. aureus or up to 48 h for E. coli. Mixed micelles were confirmed to have prolonged bacteriostatic activity for up to 72 h against both bacteria. This trend was also proven by the modified Gompertz model. An optimized P188/P407/eugenol micelle was successfully used as a model system for release study with a particle size of less than 30 nm and high encapsulation efficiency surpassing 90%. The developed mixed micelles were proved to have antibiofilm activity, and thus they provide an innovative approach for controlled release with potential in topical applications.

Inhibition mechanism of crude lipopeptide from Bacillus subtilis against Aeromonas veronii growth, biofilm formation, and spoilage of channel catfish flesh

Aeromonas veronii is associated with food spoilage and some human diseases, such as diarrhea, gastroenteritis, hemorrhagic septicemia or asymptomatic and even death. This research investigated the mechanism of the growth, biofilm formation, virulence, stress resistance, and spoilage potential of Bacillus subtilis lipopeptide against Aeromonas veronii. Lipopeptides suppressed the transmembrane transport of Aeromonas veronii by changing the cell membrane's permeability, the structure of membrane proteins, and Na+/K+-ATPase. Lipopeptide significantly reduced the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) by 86.03% and 56.12%, respectively, ultimately slowing Aeromonas veronii growth. Lipopeptides also restrained biofilm formation by inhibiting Aeromonas veronii motivation and extracellular polysaccharide secretion. Lipopeptides downregulated gene transcriptional levels related to the virulence and stress tolerance of Aeromonas veronii. Furthermore, lipopeptides treatment resulted in a considerable decrease in the extracellular protease activity of Aeromonas veronii, which restrained the decomposing of channel catfish flesh. This research provides new insights into lipopeptides for controlling Aeromonas veronii and improving food safety.

Eugenol-Based Polymeric Materials-Antibacterial Activity and Applications

Eugenol (4-Allyl-2-methoxy phenol) (EUG) is a plant-derived allyl chain-substituted guaiacol, widely known for its antimicrobial and anesthetic properties, as well as the ability to scavenge reactive oxygen species. It is typically used as a mixture with zinc oxide (ZOE) for the preparation of restorative tooth fillings and treatment of root canal infections. However, the high volatility of this insoluble-in-water component of natural essential oils can be an obstacle to its wider application. Moreover, molecular eugenol can be allergenic and even toxic if taken orally in high doses for long periods of time. Therefore, a growing interest in eugenol loading in polymeric materials (including the encapsulation of molecular eugenol and polymerization of EUG-derived monomers) has been noted recently. Such active macromolecular systems enhance the stability of eugenol action and potentially provide prolonged contact with pathogens without the undesired side effects of free EUG. In this review, we present an overview of methods leading to the formation of macromolecular derivatives of eugenol as well as the latest developments and further perspectives in their pharmacological and antimicrobial applications.

In situ generation of H2O2 using CaO2 as peroxide storage depot for haloperoxidase mimicry with surface-tailored Bi-doped mesoporous CeO2 nanozymes

Designing the size, morphology and interfacial charge of catalyst particles at the nanometer scale can enhance their performance. We demonstrate this with nanoceria which is a functional mimic of haloperoxidases, a group of enzymes that halogenates organic substrates in the presence of hydrogen peroxide. These reactions in aqueous solution require the presence of H₂O₂. We demonstrate in situ generation of H₂O₂ from a CaO₂ reservoir in polyether sulfone (PES) and poly(vinylidene fluoride) (PVDF) polymer beads, which circumvents the external addition of H₂O₂ and expands the scope of applications for haloperoxidase reactions. The catalytic activity of nanoceria was enhanced significantly by Bi³⁺ substitution. Bi-doped mesoporous ceria nanoparticles with tunable surface properties were prepared by changing the reaction time. Increasing reaction time increases the surface area S_BET of the mesoporous Bi_0.2Ce_0.8O_1.9 nanoparticles and the Ce³⁺/Ce⁴⁺ ratio, which is associated with the ζ-potential. In this way, the catalytic activity of nanoceria could be tuned in a straightforward manner. H₂O₂ required for the reaction was released steadily over a long period of time from a CaO₂ storage depot incorporated in polyether sulfone (PES) and poly(vinylidene fluoride) (PVDF) beads together with Bi_0.2Ce_0.8O_1.9 particles, which may be used as precision fillers and templates for biological applications. The spheres are prepared as a dry powder with no surface functionalization or coatings. They are inert, chemically stable, and safe for handling. The feasibility of this approach was demonstrated using a haloperoxidase assay.

Antimicrobial Compounds in Food Packaging

This review presents current knowledge on antimicrobial agents that are already used in the food packaging industry. At the beginning, innovative ways of food packaging were discussed, including how smart packaging differs from active packaging, and what functions they perform. Next, the focus was on one of the groups of bioactive components that are used in these packaging, namely antimicrobial agents. Among the antimicrobial agents, we selected those that have already been used in packaging and that promise to be used elsewhere, e.g., in the production of antimicrobial biomaterials. Main groups of antimicrobial agents (i.e., metals and metal oxides, organic acids, antimicrobial peptides and bacteriocins, antimicrobial agents of plant origin, enzymes, lactoferrin, chitosan, allyl isothiocyanate, the reuterin system and bacteriophages) that are incorporated or combined with various types of packaging materials to extend the shelf life of food are described. The further development of perspectives and setting of new research directions were also presented.

Frontiers on Sustainable Food Packaging

The implementation of sustainable food packaging solutions within future circular food supply chains is essential to protect customers and ensure food quality, safety, and optimal shelf-life [...].

Recent Advances in PLA-Based Antibacterial Food Packaging and Its Applications

In order to reduce environmental pollution and resource waste, food packaging materials should not only have good biodegradable ability but also effective antibacterial properties. Poly(lactic acid) (PLA) is the most commonly used biopolymer for food packaging applications. PLA has good physical properties, mechanical properties, biodegradability, and cell compatibility but does not have inherent antibacterial properties. Therefore, antibacterial packaging materials based on PLA need to add antibacterial agents to the polymer matrix. Natural antibacterial agents are widely used in food packaging materials due to their low toxicity. The high volatility of natural antibacterial agents restricts their application in food packaging materials. Therefore, appropriate processing methods are particularly important. This review introduces PLA-based natural antibacterial food packaging, and the composition and application of natural antibacterial agents are discussed. The properties of natural antibacterial agents, the technology of binding with the matrix, and the effect of inhibiting various bacteria are summarized.

Bioconjugated Thymol-Zinc Oxide Nanocomposite as a Selective and Biocompatible Antibacterial Agent against Staphylococcus Species

Owing to the rapid spread of antibiotic resistance among Staphylococcus species, effective and low-risk alternatives to antibiotics are being actively searched. Thymol (THO), the most abundant component of the oil extracted from thyme, can be considered as a natural antibacterial alternative. However, the low antibacterial activity and non-selectivity of THO limit its usage as a universal anti-Staphylococcus agent. Herein, we report the bioconjugation of THO with ZnO nanoparticle (ZO), which resulted in the TZ nanocomposite (NC), as a potent and selective antibacterial agent against Staphylococcus species, particularly S. epidermidis. The cell-free supernatant (CFS) of ATCC 25923 cultures was employed for the production of TZ NC. Successful production of TZ NC was confirmed via X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet-visible (UV-Vis) studies. TZ NC had selective efficacy against Staphylococcus species, with MIC values 2-32-fold lower than THO. The antibacterial mechanisms of TZ NC are proposed to involve membrane rupture, suppression of biofilm formation, and modulation of new cell wall and protein-synthesis-associated cellular pathways. Its biocompatibility against HCT116 cells was also checked. Our findings suggest that the TZ nanocomposite could improve the selectivity and bactericidal activity of THO against target species.