Antioxidant and antimicrobial properties of ethylene vinyl alcohol copolymer films based on the release of oregano essential oil and green tea extract components

Biodegradable and antibacterial edible films based on egg yolk granules/gelatin/CMC with e-poly-l-lysine: Application in fresh chicken meat preservation

Novel biodegradable and antibacterial edible films were fabricated by incorporating E-poly-l-lysine (EPL) into egg yolk granules, gelatin, and sodium carboxymethyl cellulose matrices. With increasing EPL concentration (0.3-0.9 %), water vapor permeability decreased to 0.215 ± 0.005 g.mm/m2.h.Kpa, while the water contact angle increased to 79.8°, enhancing transparency. X-ray diffraction, attenuated total reflectance-Fourier transform infrared spectroscopy, and scanning electron microscopy revealed the uniform dispersion of the EPL in the matrix, likely due to enhanced intermolecular interaction. The 0.9 %-EPL film exhibited strong antimicrobial activity and biodegraded in soil within seven days. Additionally, chicken meat packaged with films was stored at 4 °C for 8 days. Results showed that the 0.9 %-EPL film significantly reduced the thiobarbituric acid reactive substances, pH, and total viable count, thereby extending its shelf life. In summary, the EPL-enhanced egg yolk granules/gelatin/CMC edible film exhibits significant potential as an eco-friendly antimicrobial packaging material.

Effect of different modified potato starch on starch-based films containing ZIF-67@thymol

Zeolite imidazolate framework-67 (ZIF-67) was used to encapsulate thymol (THY) to improve the properties of potato starch films. The effect of different modified potato starches (acetate starch (AS), hydroxypropyl di-starch phosphate (HDSP), oxidized hydroxypropyl starch (OHS), and acetylated di-starch phosphate (ADSP)) on the film properties was investigated. The results showed that the modified potato starch film had better water resistance, mechanical property, and water vapor barrier than the natural potato starch film. Scanning electron microscopy observations showed that the smoothness of the modified film was advanced. Notably, the OHS film had the best oxidation resistance activity of 76.93 % compared to the other four films. Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were significantly inhibited in all potato starch films enhanced with ZIF-67@THY. Therefore, starch-based films incorporating ZIF-67@THY have a broad application prospect in food packaging.

Construction of magnetic response nanocellulose particles to realize smart antibacterial of Pickering emulsion

Smart antibacterial Pickering emulsion can respond to the stimulation of environmental conditions to control the release of antibacterial agents, protecting the quality and safety of food. In this study, Fe3O4 was grafted on the cellulose nanocrystal (CNC) via ultrasound-assisted in situ co-precipitation to synthesize the magnetic cellulose nanocomposite particles. When the ratio of FeCl3 and FeCl2 was 1.5:1, the prepared particles CNC/Fe1.5 exhibited the maximum saturation magnetization intensity of 54.98 emu/g and good emulsion stability, which was used to emulsify oregano essential oil (OEO) to fabricate smart antibacterial Pickering emulsion with magnetically responsive ability. The emulsion with the oil-water ratio of 3:7 and the particle concentration of 0.3 wt% showed the excellent stability and sensitive responsiveness of magnetic. The OEO released rapidly within 0-8 h followed by the slow release when the emulsion was stimulated by 0.2 T, 0.4 T and 0.6 T magnetic field. The antibacterial rate of the emulsion was close to 100 % against both E. coli and L. monocytogenes at magnetic field with 0.4 T and 0.6 T in 12 h, achieving the smart antimicrobial. The prepared smart antibacterial Pickering emulsion would provide a novel material and have the potential in food packaging.

Encapsulation of Thymol in Ethyl Cellulose-Based Microspheres and Evaluation of Its Sustained Release for Food Applications

Food waste is a global concern with enormous economic, environmental and social impacts that has contributed to active packaging evolution. However, incorporating bioactive substances into the packaging can deteriorate its physicochemical and mechanical characteristics. Thus, the objective of this work was to entrap the natural bioactive compound thymol into microparticles and apply them in the form of pads for the controlled release of bioactivity in food packaging material. The physicochemical characteristics and bioactivity of five different ethyl cellulose-based microparticles were evaluated. Increasing the amount of thymol in the formulation led to higher encapsulation efficiency. Encapsulation resulted in a substantial increase of >10-20 °C in the volatilization temperature of thymol, and the release of thymol occurred following a sustained profile, best described by the Higuchi release kinetic model. Increasing the polymer to thymol ratio in the microparticles resulted in higher thermal stability and a more gradual release profile. While all formulations demonstrated considerable inhibition of E. coli growth, the ones with the highest thymol content maintained their antimicrobial activity for at least one month of microparticle storage. Furthermore, the ability of the microparticles in retaining pH and titratable acidity of cherry tomatoes was evaluated, and it was confirmed that these characteristics were maintained during 21 days of storage.

Oregano essential oil-infused mucin microneedle patch for the treatment of hypertrophic scar

Hypertrophic scar (HS) manifests as abnormal dermal myofibroblast proliferation and excessive collagen deposition, leading to raised scars and significant physical, psychological, and financial burdens for patients. HS is difficult to cure in the clinic and current therapies lead to recurrence, pain, and side effects. In this study, a natural amphiphilic polymer mucin is used to prepare a dissolving microneedle (muMN) that is loaded with oregano essential oil (OEO) for HS therapy. muMN exhibits sufficient skin/scar tissue penetration, quick skin recovery time after removal, good loading of natural essential oil, fast dissolution and detachment from the base layer, and good biocompatibility to applied skin. In the rabbit HS model, OEO@muMN shows a significant reduction in scar thickness, epidermal thickness index, and scar elevation index. OEO@muMN also attenuates the mean collagen area fraction and decreases the number of capillaries in scar tissues. Biochemical Assay reveals that OEO@muMN significantly inhibits the expression of transforming growth factor-β1 (TGF-β1) and hydroxyproline (HYP). In summary, this study demonstrates the feasibility and good efficacy of using the anti-proliferative and anti-oxidative OEO for HS treatment. OEO@muMN is an efficient formulation that holds the potential for clinical anti-HS application. muMN is an efficient platform to load and apply essential oils transdermally.

Changes in amino acids, catechins and alkaloids during the storage of oolong tea and their relationship with antibacterial effect

The storage process has a significant impact on tea quality. Few is known about effect of storage on quality of oolong tea. This study aimed to assess the effect of different storage times on the key chemical components of oolong tea by measuring changes in catechin, free amino acid, and alkaloid content. Variation in the main substances was determined by principal component analysis and heat map analysis. The results revealed notable effects of the storage process on the levels of theanine, epigallocatechin gallate (EGCG), and glutamine. These findings suggest that these compounds could serve as indicators for monitoring changes in oolong tea quality during storage. Additionally, the study observed an increase in the antibacterial ability of tea over time. Correlation analysis indicated that the antibacterial ability against Micrococcus tetragenus and Escherichia coli was influenced by metabolites such as aspartic acid, threonine, serine, gamma-aminobutyric acid, ornithine, alanine, arginine, and EGCG. Overall, this study presents an approach for identifying key metabolites to monitor tea quality effectively with relatively limited data.

Linden-based mucilage biodegradable films: A green perspective on functional and sustainable food packaging

This study focuses on the utilization of linden mucilage, extracted from the linden tree, as a potential natural polymer source for the production of composite films. The films, which incorporating linden water extract, essential oil, and oil, exhibited improved thermal stability, surface morphology, and water resistance. Biodegradability assessments, particularly for films using essential oil and oil, showed promising outcomes by maintaining structural integrity. Antimicrobial assays demonstrated significant resistance against pathogens, indicating potential applications requiring microbial resistance. Mechanical analyses revealed a trade-off between tensile strength and elongation at break with addition of components. Composite films exhibited reduced water vapor permeability which correlate with water solubility and contact angle measurements. Soil biodegradation studies highlighted the films' potential to mitigate environmental impact. Cytotoxicity tests confirmed the safety of these films for potential food applications. Additionally, antioxidant assays showed increased radical scavenging activity in films with added components. In conclusion, linden-based composite films exhibit promising characteristics, suggesting their potential as sustainable and functional materials, particularly for use in food packaging.

Physicochemical Characterisation of Polysaccharide Films with Embedded Bioactive Substances

In this study, sodium carboxymethyl cellulose (CMCNa) bioactive films, crosslinked with citric acid (CA), were prepared and comprehensively examined for their suitability in various applications, focusing on food packaging. The films displayed favourable properties, including appropriate thickness, transparency, and moisture content, essential for packaging purposes. Moreover, the films exhibited excellent moisture absorption rate and barrier properties, attributed to the high concentration of CMCNa and the inclusion of a CA. These films presented no significant effect of crosslinking and bioactive components on their mechanical strength, as evidenced by tensile strength and elongation at break values. Thermal stability was demonstrated in the distinct weight loss events at different temperature ranges, with crosslinking contributing to slightly enhanced thermal performance. Furthermore, the films showed varying antioxidant activity levels, influenced by temperature and the solubility of the films in different media, indicating their potential for diverse applications. Overall, these bioactive films showed promise as versatile materials with desirable properties for food packaging and related applications, where the controlled release of bioactive components is advantageous for enhancing the shelf life and safety of food products. These findings contribute to the growing research in biodegradable and functional food packaging materials.

Development of Low-Density Polyethylene Films Coated with Phenolic Substances for Prolonged Bioactivity

The current study proposes an efficient coating methodology for the development of low-density polyethylene (LDPE) films with prolonged bioactivity for food packaging applications. Three natural phenolic-based substances were incorporated at optimized concentrations in methyl-cellulose-based solutions and used as coatings on LDPE films. The amount of surfactant/emulsifier was optimized to control the entrapment of the bioactive substances, minimizing the loss of the substances during processing, and offering prolonged bioactivity. As a result, the growth of Escherichia coli was substantially inhibited after interaction with the coated films, while coated films presented excellent antioxidant activities and maintained their mechanical performance after coating. Considerable bioactivity was observed after up to 7 days of storage in sealed bags in the case of carvacrol- and thymol-coated films. Interestingly, films coated with olive-leaf extract maintained a high level of antimicrobial and antioxidant properties, at least for 40 days of storage.

Antioxidant and Antibacterial Activity of Mexican Oregano Essential Oil, Extracted from Plants Occurring Naturally in Semiarid Areas and Cultivated in the Field and Greenhouse in Northern Mexico

In recent years, the determination of the antioxidant and antibacterial activity of essential oils in wild plants, such as Mexican oregano (Lippia graveolens Kunth), has become increasingly important. The objective was to compare the antioxidant and antibacterial activity of Mexican oregano essential oil obtained from plants occurring naturally in semiarid areas (Wild1 and Wild2), and those cultivated in the field (CField) and greenhouse (CGreenhouse) in northern Mexico. The Mexican oregano essential oil extraction was performed using the hydrodistillation method, the antioxidant activity was determined using the ABTS method, and the antibacterial activity was assessed through bioassays under the microwell method at nine different concentrations. The aim was to determine the diameter of the inhibition zone and, consequently, understand the sensitivity level for four bacterial species. The results revealed an antioxidant activity ranging from 90% to 94% at the sampling sites, with Wild1 standing out for having the highest average antioxidant activity values. Likewise, six out of the nine concentrations analyzed showed some degree of sensitivity for all the sampling sites. In this regard, the 25 µL mL-1 concentration showed the highest diameter of inhibition zone values, highlighting the Wild2 site, which showed an average diameter greater than 30 mm for the four bacteria tested. Only in the case of S. typhi did the CGreenhouse site surpass the Wild2, with an average diameter of the inhibition zone of 36.7 mm. These findings contribute to the search for new antioxidant and antibacterial options, addressing the challenges that humanity faces in the quest for opportunities to increase life expectancy.

Salvia sclarea Essential Oil Chemical Composition and Biological Activities

Salvia sclarea essential oil (SSEO) has a long tradition in the food, cosmetic, and perfume industries. The present study aimed to analyze the chemical composition of SSEO, its antioxidant activity, antimicrobial activity in vitro and in situ, antibiofilm, and insecticidal activity. Besides that, in this study, we have evaluated the antimicrobial activity of SSEO constituent (E)-caryophyllene and standard antibiotic meropenem. Identification of volatile constituents was performed by using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) techniques. Results obtained indicated that the main constituents of SSEO were linalool acetate (49.1%) and linalool (20.6%), followed by (E)-caryophyllene (5.1%), p-cimene (4.9%), a-terpineol (4.9%), and geranyl acetate (4.4%). Antioxidant activity was determined as low by the means of neutralization of the DDPH radical and ABTS radical cation. The SSEO was able to neutralize the DPPH radical to an extent of 11.76 ± 1.34%, while its ability to decolorize the ABTS radical cation was determined at 29.70 ± 1.45%. Preliminary results of antimicrobial activity were obtained with the disc diffusion method, while further results were obtained by broth microdilution and the vapor phase method. Overall, the results of antimicrobial testing of SSEO, (E)-caryophyllene, and meropenem, were moderate. However, the lowest MIC values, determined in the range of 0.22–0.75 µg/mL for MIC50 and 0.39–0.89 µg/mL for MIC90, were observed for (E)-caryophyllene. The antimicrobial activity of the vapor phase of SSEO (towards microorganisms growing on potato) was significantly stronger than that of the contact application. Biofilm analysis using the MALDI TOF MS Biotyper showed changes in the protein profile of Pseudomonas fluorescens that showed the efficiency of SSEO in inhibiting biofilm formation on stainless-steel and plastic surfaces. The insecticidal potential of SSEO against Oxycarenus lavatera was also demonstrated, and results show that the highest concentration was the most effective, showing insecticidal activity of 66.66%. The results obtained in this study indicate the potential application of SSEO as a biofilm control agent, in the shelf-life extension and storage of potatoes, and as an insecticidal agent.

Evaluation of Active LDPE Films for Packaging of Fresh Orange Juice

Microbial development, enzymatic action, and chemical reactions influence the quality of untreated natural orange juice, compromising its organoleptic characteristics and causing nutritional value loss. Active low-density polyethylene (LDPE) films containing green tea extract (GTE) were previously prepared by a blown film extrusion process. Small bags were prepared from the produced films, which were then filled with fresh orange juice and stored at 4 °C. Ascorbic acid (AA) content, sugar content, browning index, color parameters, pH, total acidity (TA) and microbial stability were evaluated after 3, 7, and 14 days of storage. The packaging containing GTE maintained the microbial load of fresh juice beneath the limit of microbial shelf-life (6 log CFU/mL) for the bacterial growth, with a more prominent effect for LDPE with 3%GTE. Regarding yeasts and molds, only the CO_LDPE_3GTE package maintained the microbial load of fresh juice below the limit for up to 14 days. At 14 days, the lowest levels of AA degradation (32.60 mg/100 mL of juice) and development of brown pigments (browning index = 0.139) were observed for the packages containing 3% of GTE, which had a pH of 3.87 and sugar content of 11.4 g/100 mL of juice at this time. Therefore, active LDPE films containing 3% of GTE increase the shelf-life of fresh juice and can be a promising option for storage of this food product while increasing sustainability.

Pilot-Scale Processing and Functional Properties of Antifungal EVOH-Based Films Containing Methyl Anthranilate Intended for Food Packaging Applications

Antimicrobial packaging has emerged as an efficient technology to improve the stability of food products. In this study, new formulations based on ethylene vinyl alcohol (EVOH) copolymer were developed by incorporating the volatile methyl anthranilate (MA) at different concentrations as antifungal compound to obtain active films for food packaging. To this end, a twin-screw extruder with a specifically designed screw configuration was employed to produce films at pilot scale. The quantification analyses of MA in the films showed a high retention capacity. Then, the morphological, optical, thermal, mechanical and water vapour barrier performance, as well as the antifungal activity in vitro of the active films, were evaluated. The presence of MA did not affect the transparency or the thermal stability of EVOH-based films, but decreased the glass transition temperature of the copolymer, indicating a plasticizing effect, which was confirmed by an increase in the elongation at break values of the films. Because of the additive-induced plasticization over EVOH, the water vapour permeability slightly increased at 33% and 75% relative humidity values. Finally, the evaluation of the antifungal activity in vitro of the active films containing methyl anthranilate showed a great effectiveness against P. expansum and B. cinerea, demonstrating the potential applicability of the developed films for active food packaging.

Fabrication of active whey Protein isolate/oleic acid emulsion based film as a promising bio-material for cheese packaging

Emulsion is a colloidal dispersion for delivering natural antimicrobial, antioxidant, and bioactive compounds to improve the product's quality. The present study aimed to develop the active emulsion film based on whey protein isolate (WPI) by adding oleic acid (OA) (0, 10, and 20% w/w) and green tea extract (GTE) (0 and 0.5% w/v) for cheese packaging. Results showed that the opacity, flexibility, and water barrier properties of WPI hydrogel-based film were significantly increased by adding 10% OA. Active release from emulsion-based films was governed by pH and the nature of food model systems. The minimum release occurred in the acidic food model system. After 5 h exposure in the acid food model system, the obtained release from the active film containing OA 0, 10, and 20% was 52.39, 48.97, and 57.24% of incorporated GTE, respectively. The log reduction value (LRV) of active emulsion film against bacteria was significantly affected by the food model system. Moreover, packed lactic coagulated cheese delivered more phenolic compound of GTE than processed spread cheese. Korsmeyer-Peppas model and Weibull with lag were suggested as appropriate models to forecast the release kinetic of GTE.

Antibacterial Effect of Oregano Essential Oil against Vibrio vulnificus and Its Mechanism

Oregano essential oil (OEO) is an effective natural antibacterial agent, but its antibacterial activity against Vibrio vulnificus has not been widely studied. The aim of this study was to investigate the inhibitory effect and germicidal activity of OEO on V. vulnificus and its possible inhibition mechanism. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of OEO against four V. vulnificus strains (ATCC 27562 and three isolates from seafoods) were from 0.06 to 0.15 μL/mL. Compared with untreated bacteria, OEO reduced the concentration of intracellular adenosine triphosphate (ATP), hyperpolarized the cell membrane, increased the level of reactive oxygen species (ROS), and increased the concentration of intracellular malondialdehyde (MDA), but there was no obvious DNA damage at the OEO test concentration. It was indicated that OEO inactivated V. vulnificus by generating ROS which caused lipid peroxidation of cell membranes, thereby reducing the permeability and integrity of cell membranes and causing morphological changes to cells, but there was no obvious damage to DNA. In addition, OEO could effectively kill V. vulnificus in oysters at 25 °C, and the number of bacteria decreased by 48.2% after 0.09% OEO treatment for 10 h. The good inhibitory effect and bactericidal activity of OEO showed in this study, and the economy and security of OEO make it possible to apply OEO to control V. vulnificus contamination in oysters and other seafoods.

Multifunctional poly(vinyl alcohol) films using cellulose nanocrystals/oregano and cellulose nanocrystals/cinnamon Pickering emulsions: Effect of oil type and concentration

Poly (vinyl alcohol) (PVA) films with high transparency, UV-barrier, antioxidant, and antimicrobial properties were prepared using oregano essential oil (OEO) and cinnamon essential oil (CEO) Pickering emulsions. The effect of Pickering emulsion type and concentration on the PVA film properties was studied. Cellulose nanocrystals (CNCs) were used as a natural stabilizer to prepare OEO and CEO Pickering emulsions. Both emulsions showed spherical droplets with diameters of 155-291 nm, zeta potential of -36.2 to -49.6 mV, minimum inhibition concentration of 6.25-12.5 μL/mL, and inhibition zone of 40-65 mm, depending on oil type. Morphology and FTIR analysis showed that OEO and CEO Pickering emulsions were compatible with the PVA matrix. The UV-transmittance of PVA films decreased from 77.3% to 30.4% and 2.0% without sacrificing the transparency after adding OEO and CEO Pickering emulsions, respectively. Antimicrobial results showed that E. coli was more sensitive to CEO, while S. aureus was sensitive to OEO Pickering emulsion. PVA/CEO film displayed higher properties than PVA/OEO film.

Performance of Gelatin Films Reinforced with Cloisite Na+ and Black Pepper Essential Oil Loaded Nanoemulsion

The concern about consuming eco-friendly products has motivated research in the development of new materials. Therefore, films based on natural polymers have been used to replace traditional polymers. This study consists of a production of films based on gelatin reinforced with black pepper essential oil-loaded nanoemulsions and Cloisite Na⁺. The films were characterized by water vapor permeability, mechanical and thermal properties, surface contact angle, X-ray diffraction and scanning electron microscopy. It was observed that the films containing the nanoemulsion have higher permeability values and an increase in their mechanical resistance. The addition of nanoclay contributed to an increase in the surface hydrophobicity of the film and an increase in the tensile strength, at break, by about 150%. The addition of essential oil nanoemulsions led to an increase in thermal stability. The presence of clay dispersion contributed to the formation of a surface that was slightly rougher and grainier. The addition of the black pepper essential oil nanoemulsion resulted in an increase in porosity of the gelatin matrix. Through X-ray diffraction analysis, it was possible to conclude that both the polymeric gelatin matrix and the essential oils nanoemulsion are intercalated with the clay dispersion.

Gelatine/PVA copolymer film incorporated with quercetin as a prototype to active antioxidant packaging

Films that incorporate antioxidant agents are widely used and improve the stability of food products that are prone to oxidation. This work evaluated the potential antioxidant activity of PVA/gelatine films incorporated with quercetin. The films were prepared by the casting method and characterised by TG-DSC, FTIR spectroscopy, SEM, optical microscopy and swelling index. Antioxidant properties were evaluated with DPPH, ABTS and FRAP assays. According to the thermal characterisation results, the film was stable up to 68 °C and entirely degraded at 632 °C. The FTIR spectroscopic analysis indicated that there was a physical interaction between the quercetin and the polymeric film, and microscopy indicated a homogeneous and uniform film. The film showed DPPH (315.4 ± 8.2) and ABTS radical potential activity (199.4 ± 9.7), as well as potential iron reduction activity-FRAP (740.6 ± 8.9) mainly when analysed in ethanol: water (95:5 v/v) system, all results expressed as milligram of Trolox per gram of film. Hence, PVA/gelatine films incorporated with quercetin have properties that allow a potential application in active packaging systems to delay oxidative processes in food.

Hot-Melt-Extruded Active Films Prepared from EVOH/Trans-Cinnamaldehyde Blends Intended for Food Packaging Applications

In this work, novel active films based on ethylene vinyl alcohol copolymer (EVOH) and cinnamaldehyde (CIN) were successfully obtained employing a hybrid technique consisting of a two-step protocol involving the preparation of a polymeric EVOH-CIN masterbatch by solvent-casting for its further utilization in the preparation of bioactive EVOH-based films by melt extrusion processing. The influence of CIN over the EVOH matrix was studied in terms of optical, morphological, thermal, and mechanical properties. Optically transparent films were obtained and the incorporation of cinnamaldehyde resulted in yellow-colored films, producing a blocking effect in the UV region. A decrease in the glass transition temperature was observed in the formulations containing cinnamaldehyde, indicating a plasticizing effect. This phenomenon was confirmed by an increase in the elongation at break values of the extruded films. Results from thermogravimetric analysis determined a slight decrease in the thermal stability of EVOH provoked by the vaporization of the bioactive compound. Bioactive properties of the films were also studied; the presence of residual cinnamaldehyde in EVOH after being subjected to an extrusion process conferred some radical scavenging activity determined by the DPPH assay whereas films were able to exert antifungal activity in vapor phase against Penicillium expansum. Therefore, the present work shows the potential of the hybrid technique employed in this study for the preparation of bioactive films by a ready industrial process technology for food packaging applications.

Oregano essential oil addition in rice starch films and its effects on the chilled fish storage

Active packaging produced from biodegradable polymers and essential oil could have a great value to food industries. This study aimed to evaluate the effect of the addition of oregano essential oil (OEO) on rice starch films and its application as packaging for fish fillets. Several concentrations of OEO were added to the films, the film added with 4.5% OEO showed lower permeability to water vapor 3.7 g mm kPa^-1 m^-2 day^-1, intermediate solubility of 24% and high tensile strength (4.4 MPa) while the standard film (without the addition of OEO) presented 8.8 g mm kPa^-1 m^-2 day^-1, 25.8% and 2.2 MPa, respectively. Packed fish fillets with the active film showed an increase in its shelf life when compared to the standard film. Packaged fish fillets in OEO films showed greater resistance (13.4 N), less oxidation (1.65 mg malonaldehyde/kg of sample) and less microbiological growth 10⁷ CFU/g in 6 days of storage, while packaged fish fillets in standard film showed lower resistance (10.4 N), higher oxidation (1.88 mg malonaldehyde/kg of sample) and higher microbiological growth 10⁸ CFU/g. Thus, the active packaging developed had the capacity to increase the shelf life of a perishable product that has great interest of food industries.

Litsea cubeba fruit essential oil and its major constituent citral as volatile agents in an antimicrobial packaging material

Food packaging films were coated with polyvinyl acetate (PVA) containing different concentrations of citral or Litsea (L.) cubeba essential oil (EO). Antimicrobial contact trials in style of ISO22916 were performed. Citral coatings achieved bactericidal effects against Escherichia coli (2.1 log) and Staphylococcus aureus (4.3 log) at concentrations of 20%_DM. L. cubeba inactivated more than 4 log cycles of both bacteria at a concentration of 20%_DM. To determine the antimicrobial activity across the gas phase, a unique method for volatile agents was developed, adapting ISO22196. GC/MS measurements were performed to supplement microbiological tests in a model packaging system with a defined 220 ml headspace (HS). HS-equilibrium concentrations of 1.8 μg/ml_Air were found for 20%_{DM '}citral-coatings, resulting in antimicrobial effects of 3.8 log against of E. coli. Saccharomyces cerevisiae (4.74 log) and Aspergillus niger (4.29 log) were more effectively inactivated by 3%_DM and 5%_DM coatings. In an application trial with strawberries, simulating a headspace packaging, growth inhibitory effects on the yeast and mold microbiota were found for the 20%_DM coatings.

Effect of green tea extract on gelatin-based films incorporated with lemon essential oil

The use of natural polymers, such as gelatin and other proteins, has increased in an attempt to replace part of the consumption of petroleum-based packaging. This study evaluated the influence of green tea extract and lemon nanoemulsion on mechanical, thermal and permeability properties of gelatin matrix. The results showed that green tea increased the gelatin tensile strength (TS) from 86 ± 7 MPa to 101 ± 5 MPa, on the other hand, the nanoemulsion decreases to 78 ± 8 MPa. The incorporation of green tea and nanoemulsion enhanced the water vapor permeability of gelatin film; this could be due to the interacting with the hydrophobic domains of gelatin. This was indicated by melting point (Tm) in differential scanning calorimetry (DSC) and degradation temperatures in the thermogravimetric analysis (TG), respectively. Changes in FTIR spectra of gelatin film were observed when the green tea and nanoemulsion were incorporated. Therefore, this study showed a new characterization and formulation of gelatin films incorporated by green tea extract and lemon nanoemulsion and their potential for edible film.

Melt-Processed Bioactive EVOH Films Incorporated with Ferulic Acid

In this work, antimicrobial and antioxidant films based on ethylene vinyl alcohol (EVOH) copolymer containing low amounts of ferulic acid (FA) were successfully developed by melt extrusion. Optically transparent films were obtained, and the presence of FA provided some UV blocking effect. The characterization of the thermal and barrier properties of the developed films showed that the addition of FA improved the thermal stability, decreased the glass transition temperature (Tg) and increased the water vapor and oxygen transmission rates when ferulic acid was loaded above 0.5 wt.%, associated with its plasticizing effect. Mechanical characterization confirmed the plasticizing effect by an increase in the elongation at break values while no significant differences were observed in Young's modulus and tensile strength. Significant antioxidant activity of all active films exposed to two food simulants, 10% ethanol and 95% ethanol, was also confirmed using the 2,2-diphenyl-1-pricylhydrazyl (DPPH) free radical scavenging method, indicating that FA conserved its well-known antioxidant properties after melt-processing. Finally, EVOH-FA samples presented antibacterial activity in vitro against Escherichia coli and Staphylococcus aureus, thus showing the potential of ferulic acid as bioactive compound to be used in extrusion processing for active packaging applications.

Seasonality Effects on Antibacterial and Antibiotic Potentiating Activity against Multidrug-Resistant Strains of Escherichia coli and Staphylococcus aureus and ATR-FTIR Spectra of Essential Oils from Vitex gardneriana Leaves

Plants are natural sources of several bioactive substances, which have been found in extracts, secondary metabolites, and essential oils. Several biological activities have been attributed to essential oils as antiviral, insecticidal, antiparasitic, antioxidant, and antimicrobial. The indiscriminate use of antibiotics has increased the development of resistance mechanisms of microorganisms. Thus, search for efficient natural compounds with antimicrobial activity and low toxicity has increased, so essential oils have been a promising alternative for combating microbial infections. This study was carried out to investigate the seasonality effects on the infrared absorbance spectra, antibacterial activity, and antibiotic potentiating activity of essential oils from Vitex gardneriana leaves. Essential oils were extracted from V. gardneriana Schauer leaves the seasonal period from January to December 2016 and characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The antibacterial effect of these oils and antibiotic potentiating activity, both determined by the minimum inhibitory concentration, were assessed using microtiter plates. For the first time, we present the use of infrared absorbance spectra of these essential oils and show the influence of seasonality on them. Synergistic effects were observed for the essential oils associated with the antibiotics tested (gentamicin, ampicillin, and ofloxacin). The main influence of seasonality on the infrared absorbance spectra of the essential oils of the V. gardneriana occurred in the June month (last month of the rainy season). In regard to antibacterial activity test, the essential oils of the V. gardneriana leaves did not show a direct effect on the strains tested. However, the essential oils when associated with the antibiotics showed variations in the minimum inhibitory concentration with the months of the seasonal period, indicating synergistic effects against Escherichia coli and Staphylococcus aureus bacterial resistance.

Potential Application of Essential Oils for Mitigation of Listeria monocytogenes in Meat and Poultry Products

One of the most important challenges in the food industry is to provide healthy and safe food. Therefore, it is not possible to achieve this without different processes and the use of various additives. In order to improve safety and extend the shelf life of food products, various synthetic preservatives have been widely utilized by the food industry to prevent growth of spoilage and pathogenic microorganisms. On the other hand, consumers' preference to consume food products with natural additives induced food industries to use natural-based preservatives in their production. It has been observed that herbal extracts and their essential oils could be potentially considered as a replacement for chemical antimicrobials. Antimicrobial properties of plant essential oils are derived from some main bioactive components such as phenolic acids, terpenes, aldehydes, and flavonoids that are present in essential oils. Various mechanisms such as changing the fatty acid profile and structure of cell membranes and increasing the cell permeability as well as affecting membrane proteins and inhibition of functional properties of the cell wall are effective in antimicrobial activity of essential oils. Therefore, our objective is to revise the effect of various essential oils and their bioactive components against Listeria monocytogenes in meat and poultry products.

Extraction Techniques and Analytical Methods for Characterization of Active Compounds in Origanum Species

Phytochemical research based on ethnopharmacology is gaining interest in industries such as functional food, nutraceuticals, cosmetics and pharmaceutical industries. Plants and plant extracts are a rich source of bioactive secondary metabolites. These compounds are often involved in plant protection against biotic or abiotic stresses. The exploitation of available technologies should be oriented and intensified to extend and enhance the continued usefulness of the plants as renewable sources of chemicals, especially medicinal compounds. This current contribution is focused on extraction and analytical techniques for their isolation from the oregano species, their characterization and their potential antioxidative, as well as their antimicrobial, antifungal and anticarcinogenic properties. The work is structured rendering to the different steps involved in the research; starting with extraction and sample preparation, followed by discussing the analytical techniques employed for the isolation and identification of compound/s responsible for the biological activity and methods and techniques for biological activity assessment.

Antioxidant Packaging Films Based on Ethylene Vinyl Alcohol Copolymer (EVOH) and Caffeic Acid

The main objective of this research activity was to design and realize active films with tunable food functional properties. In detail, caffeic acid (CA), a polyphenol with high antioxidant effect, was used as active ingredient in poly (vinyl alcohol-co-ethylene) (EVOH) films at 5 wt.% and 15 wt.% and successfully realized by means of the solvent casting process. Optical, morphological, thermal and mechanical studies were considered to define the effect of the presence of the CA component on the structural properties of the matrix. In addition, moisture content and antioxidant activity were evaluated, to have clear information on the CA effect in terms of functional characteristics of realized food packaging systems. Results from tensile tests showed increased values for strength and deformation at break in EVOH_CA based films. Results from colorimetric and transparency analysis underlined that the presence of caffeic acid in EVOH copolymer induces some alterations, whereas the addition of the active ingredient determined a positive radical scavenging activity of the formulations, confirming the possibility of practically using these polymeric systems in the food packaging sector.

Biodegradable Poly(ε-Caprolactone) Active Films Loaded with MSU-X Mesoporous Silica for the Release of α-Tocopherol

In this study, new active PCL (poly(ε-caprolactone)) films containing α-tocopherol (TOC) and MSU-X mesoporous silica were prepared by melt blending. The studied additives were directly incorporated into the polymer matrix or by impregnating TOC into MSU-X silica (PCL-IMP). Thermal, optical, oxygen and water barrier properties as well as oxidation onset parameters, were studied. Films containing MSU-X and/or TOC showed a significant increase in oxidative onset temperature (OOT) and oxidative induction time (OIT), improving thermal stability against materials oxidation by the addition of mesoporous silica and TOC into the polymer matrix. In addition, the effect of MSU-X addition on the migration behaviour of α-tocopherol from active films was investigated at 40 °C using 50% (v/v) ethanol as fatty food simulant, showing PCL-IMP films the lower release content and diffusion coefficient (3.5 × 10⁻¹⁵ cm² s⁻¹). Moreover, radical scavenging (DPPH and ABTS) and antibacterial activity against E. coli and S. aureus were favoured by the release of α-tocopherol in the developed films. The obtained results have demonstrated the potential of the new PCL-based active formulations for TOC controlled release in antioxidant and antibacterial food packaging applications.