In vitro antibacterial and antioxidant properties of chitosan edible films incorporated with Thymus moroderi or Thymus piperella essential oils

Plant Secondary Metabolite-Derived Polymers: A Potential Approach to Develop Antimicrobial Films

The persistent issue of bacterial and fungal colonization of artificial implantable materials and the decreasing efficacy of conventional systemic antibiotics used to treat implant-associated infections has led to the development of a wide range of antifouling and antibacterial strategies. This article reviews one such strategy where inherently biologically active renewable resources, i.e., plant secondary metabolites (PSMs) and their naturally occurring combinations (i.e., essential oils) are used for surface functionalization and synthesis of polymer thin films. With a distinct mode of antibacterial activity, broad spectrum of action, and diversity of available chemistries, plant secondary metabolites present an attractive alternative to conventional antibiotics. However, their conversion from liquid to solid phase without a significant loss of activity is not trivial. Using selected examples, this article shows how plasma techniques provide a sufficiently flexible and chemically reactive environment to enable the synthesis of biologically-active polymer coatings from volatile renewable resources.

Antimicrobial Activity of Chitosan Film Forming Solution Enriched with Essential Oils; an in Vitro Assay

Background: The resistance of the bacteria and fungi to the innumerous antimicrobial agents is a major challenge in the treatment of the infections demands to the necessity for searching and finding new sources of substances with antimicrobial properties. The incorporation of the essential oils (EOs) in chitosan film forming solution may enhance antimicrobial properties. However, its use as the feeding additive in the poultry nutrition needs to clarify the product's activity against both pathogen and the useful microbes in the gastrointestinal tract. Objectives: In the present study, we carried out an in vitro investigation and evaluated the antimicrobial activity of chitosan film forming solution incorporated with essential oils (CFs+EOs) against microbial strains including Staphylococcus aureus, Escherichia coli, Enterococcus faecium, Lactobacillus rahmnosus, Aspergillus niger and Alternaria alternate. Material and Methods: In three replicates, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of different treatments including: 1- essential oils (EOs), 2- chitosan film solution (CFs), and 3-chitosan film solution enriched with EOs (CFs+EOs) were determined against above mentioned microbes. Results: The results indicated that the chitosan solution enriched with essential oils (CFs+EOs) is capable of inhibiting the bacterial and fungal growth even at the lowest concentrations. The MIC and MBC for all the antimicrobial agents against Escherichia coli and Staphylococcus aureus were very low compared to the concentrations needed to inhibit the growth of useful bacteria, Lactobacillus rahmnosu and Enterococcus faecium. The antifungal activity of chitosan was enhanced as the concentration of EOs increased in the film solution. Conclusion: Chitosan-EOs complexes are the promising candidate for novel contact antimicrobial agents that can be used in animal feeds.

Fabrication and characterization of electrospun gelatin nanofibers crosslinked with oxidized phenolic compounds

In this study, the ability of oxidized phenolic compounds of tannic, gallic, ferulic and caffeic acids to crosslink gelatin (G) was investigated. The electrospun crosslinked gelatin nanofibers were assessed in terms of gelatin solution properties, fiber morphology, thermal properties, FTIR spectra, XRD pattern and antioxidant activity. Tannic acid showed the most crosslinking activity towards gelatin (13.3 vs 7.44, 4.65, and 3.45% for caffeic, gallic and ferulic, respectively). Crosslinking enhanced roughly electrical conductivity of gelatin solution while the surface tension and viscosity reduced. According to scanning electron microscopy (SEM) results, the fibrous structure of crosslinked gelatin nanofibers didn't change while their diameter increased to the highest value of 280nm for gelatin-tannic. Gelatin-gallic sample showed the highest total phenolic content (86.3mg gallic acid equivalent/g) and antioxidant activity (86.5%). Surprisingly, from differential scanning calorimetry (DSC) curves, it was found that crosslinking led to the reduction of thermal stability of gelatin nanofibers.

Impact of bioactive packaging systems based on EVOH films and essential oils in the control of aflatoxigenic fungi and aflatoxin production in maize

Aspergillus flavus and A. parasiticus are the most common fungal species associated with aflatoxin (AF) contamination of cereals, especially maize, and other agricultural commodities. AFB_1, the most frequent and toxic metabolite, is a powerful hepatotoxic, teratogenic and mutagenic compound. Effective strategies to control these fungal species and AFs in food and feed are required. Active packaging film containing essential oils (EO) is one of the most innovative food packaging concepts. In this study, ethylene-vinyl alcohol (EVOH) copolymer films incorporating EO from Origanum vulgare (ORE), Cinnamomum zeylanicum (CIN) or their major active constituents, carvacrol (CAR) and cinnamaldehyde (CINHO), respectively, were developed and assayed to control growth of A. flavus and A. parasiticus and AF production in maize grains under different a_w and temperature regimens. EO doses assayed in cultures were in the range 0.25-4.0mg/Petri dish. The factors a_w, temperature, type of EVOH-EO film and fungal species significantly influenced the ED₅₀ values of all assayed films. Growth rate (GR) of both species was usually higher at 0.99 than at 0.96 a_w and at 37°C than at 25°C. However, the contrary was found with regard to AF production. The order of efficacy of EVOH-EO films to control growth of both species and AF production was EVOH-CINHO>EVOH-CAR>EVOH-ORE>EVOH-CIN. The effective dose (ED₅₀) (mg EO/plate) for EVOH-CINHO and EVOH-CIN films against A. flavus were in the ranges of 0.125 and 2.475-3.500 and against A. parasiticus in the ranges of 0.121-0.133 and 2.275-3.625, respectively. Under the assayed conditions, the ED₉₀ for EVOH-CINHO film were 0.22-0.23mg/plate for both species. It was the most effective bioactive film to control fungal growth (vapour phase) and AF production, regardless of a_w and temperature. This is the first study about the impact that interacting environmental conditions and bioactive EVOH-CINHO, EVOH-ORE, EVOH-CIN EVOH-CAR films have on the growth of aflatoxigenic fungi and on AF production in maize grains.

Application of a puffer fish skin gelatin film containing Moringa oleifera Lam. leaf extract to the packaging of Gouda cheese

This study aims to develop a puffer fish skin gelatin (PSG) film that contains Moringa oleifera Lam. leaf extract (ME) as a new biodegradable film. With the increase in ME concentration, the tensile strength and elongation at break of the PSG film increased, whereas the oxygen permeability and water vapor permeability decreased. In addition, the PSG film with ME exhibited antimicrobial activity against Listeria monocytogenes and antioxidant activity. To apply the ME-containing PSG film to food packaging, Gouda cheese was wrapped with the ME-containing PSG film. During storage, the cheese packaging with the ME-containing PSG film effectively inhibited the microbial growth and retarded the lipid oxidation of cheese compared with the control sample. Thus, the ME-containing PSG film can be used as an antimicrobial and antioxidative packaging material to improve the quality of food products.

Chitosan films and coatings containing essential oils: The antioxidant and antimicrobial activity, and application in food systems

Chitosan edible films and coatings have shown great promise for their application in food preservation and also are promising systems to be used as essential oil (EO) carriers. This review reports the most recent and relevant studies concerning chitosan films and coatings containing EOs. The effect of EO incorporation on the antioxidant, antibacterial and antifungal activities of chitosan films and coatings in vitro and in vivo, as well as their applications in food systems have been discussed. In general, incorporation of EOs significantly increased the antioxidant, antibacterial and antifungal efficacy of chitosan films and coatings in vitro. EO-incorporated films and coatings also showed greater effectiveness against postharvest fungi and foodborne bacteria in food systems than pure films and coatings. The application of chitosan films and coatings containing EOs usually led to an extension of the shelf-life and reduction of lipid peroxidation of fish and meat products over pure chitosan films and coatings. In addition, chitosan coatings incorporated with EOs were more effective in maintaining fruit and vegetable quality, and controlling their postharvest decay during storage and shelf life than pure chitosan coatings.

Antimicrobial and Antioxidant Activity of Chitosan/Hydroxypropyl Methylcellulose Film-Forming Hydrosols Hydrolyzed by Cellulase

The aim of this study was to evaluate the impact of cellulase (C) on the biological activity of chitosan/hydroxypropyl methylcellulose (CH/HPMC) film-forming hydrosols. The hydrolytic activity of cellulase in two concentrations (0.05% and 0.1%) was verified by determination of the progress of polysaccharide hydrolysis, based on viscosity measurement and reducing sugar-ends assay. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging effect, the ferric reducing antioxidant power (FRAP), and microbial reduction of Pseudomonas fluorescens, Yersinia enterocolitica, Bacillus cereus, and Staphylococcus aureus were studied. During the first 3 h of reaction, relative reducing sugar concentration increased progressively, and viscosity decreased rapidly. With increasing amount of enzyme from 0.05% to 0.1%, the reducing sugar concentration increased, and the viscosity decreased significantly. The scavenging effect of film-forming solutions was improved from 7.6% at time 0 and without enzyme to 52.1% for 0.1% cellulase after 20 h of reaction. A significant effect of cellulase addition and reaction time on antioxidant power of the tested film-forming solutions was also reported. Film-forming hydrosols with cellulase exhibited a bacteriostatic effect on all tested bacteria, causing a total reduction.

Antimicrobial Active Packaging including Chitosan Films with Thymus vulgaris L. Essential Oil for Ready-to-Eat Meat

An active packaging system has been designed for the shelf life extension of ready to eat meat products. The package included an inner surface coated with a chitosan film with thyme essential oil (0%, 0.5%, 1%, and 2%) not in direct contact with the meat. Our aim was to reduce the impact of thyme essential oil (EO) on meat sensory properties by using a chemotype with low odor intensity. The pH, color parameters, microbial populations, and sensory properties were assessed during 4 weeks of refrigerated storage. The presence of EO films reduced yeast populations, whereas aerobic mesophilic bacteria, lactic acid bacteria, and enterobacteria were not affected by the presence of the EO in the films. Meat color preservation (a *) was enhanced in the presence of EO, giving a better appearance to the packaged meat. The presence of the chitosan-EO layer reduced water condensation inside the package, whereas packages containing only chitosan had evident water droplets. Thyme odor was perceived as desirable in cooked meat, and the typical product odor intensity decreased by increasing the EO concentration. Further studies should point towards developing oil blends or combinations with natural antimicrobial agents to be incorporated into the film to improve its antimicrobial properties.

Evaluation of the antibacterial and antioxidant activities of chitosan edible films incorporated with organic essential oils obtained from four Thymus species

The aims of this study were to evaluate, (1) the antibacterial properties, (2) the total phenol content and (3) the antioxidant activity, of chitosan edible films incorporated with certified organic essential oils (EOs) obtained from Thymus zygis, Thymus mastichina, Thymus capitatus and Thymus vulgaris. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films while for the antioxidant activity, two different analytical assays were used (DPPH and FRAP). As regard antibacterial activity, films containing only chitosan were not effective against any of tested bacteria. Chitosan films containing T. capitatus EO (CH + TCEO) was more effective against Listeria innocua and Alcaligenes faecalis whilst chitosan films containing T. mastichina EO (CH + TMEO) had the highest inhibition halos against Serratia marcescens. For and Enterobacter amnigenus no antibacterial activity was achieved. Chitosan films added with Thymus essential oils showed antioxidant activity, at all concentrations and with all methods assayed. CH + TZEO had the highest antioxidant activity revealed with DPPH assay. However in CH + TCEO showed best antioxidant effect when assessed with FRAP assay. The results showed that chitosan edible films incorporated with organic Thymus EOs could be used as active films in food industry due to its antibacterial and antioxidant activities.

Effect of Edible and Active Coating (with Rosemary and Oregano Essential Oils) on Beef Characteristics and Consumer Acceptability

The effects of an alginate-based edible coating containing natural antioxidants (rosemary and oregano essential oils) on lipid oxidation, color preservation, water losses, texture and pH of beef steaks during 14 days of display were studied. The essential oil, edible coating and beef antioxidant activities, and beef consumer acceptability were also investigated. The edible coatings decreased lipid oxidation of the meat compared to the control. The coating with oregano was most effective (46.81% decrease in lipid oxidation) and also showed the highest antioxidant activity. The coatings significantly decreased color losses, water losses and shear force compared to the control. The coatings had a significant effect on consumer perception of odor, flavor and overall acceptance of the beef. In particular, the oregano coating showed significantly high values (approximately 7 in a 9-point scale). Active edible coatings containing natural antioxidants could improve meat product stability and therefore have potential use in the food industry.

Essential Oils in Foods: From Ancient Times to the 21st Century

Medicinal plants and culinary herbs have been used since ancient times. Essential oils (EO) are a mixture of numerous compounds, mainly terpenes, alcohols, acids, esters, epoxides, aldehydes, ketones,aminesandsulfides,thatareprobablyproducedbyplantsasaresponsetostress[1].[...].

Bioactivity, stability and phenolic characterization of Filipendula ulmaria (L.) Maxim

The purpose of the present study was to evaluate the antioxidant and antimicrobial potential of Filipendula ulmaria (L.) Maxim. methanolic extracts, their stabilities under different pH and thermal conditions and in vitro digestibility. The results showed a considerable content of phenolic compounds in the extracts, especially total phenolic acids (47.47 mg CAE g(-1)) and flavonoids (45.47 mg RUE g(-1)) in aerial parts. HPLC analysis indicated the presence of spiraeoside in the aerial part extract. The extracts revealed an interesting antimicrobial effect against the tested microorganisms, especially bacteria E. coli and E. faecalis (MIC 0.156-0.625 mg mL(-1)), and fungi P. cyclopium and F. oxysporum (MIC 2.5-5 mg mL(-1)). The extracts exerted high antioxidant activities, particularly the root extract, paralleled by their considerable activities against the lipid oxidation process. The results of this study suggest that both extracts potentially could be functional food ingredients considering their good antioxidant and antimicrobial activities, and stability under different conditions.

Effect of edible chitosan/clove oil films and high-pressure processing on the microbiological shelf life of trout fillets

BACKGROUND

The inhibitory effect of chitosan films with clove oil (0-50 g kg(-1) ) was evaluated on a range of ten representative food spoilage and pathogenic bacteria.

RESULTS

The most sensitive bacteria to the films was Shewanella putrefaciens and the most resistant was Aeromonas hydrophila (inhibition was apparent only at 50 g kg(-1) clove essential oil (CEO)). Films with 20 g kg(-1) CEO inhibited nine of ten of the bacteria tested. Chitosan films with 20 g kg(-1) CEO were combined with high-pressure (HPP) processing as treatments for trout fillets, and changes in physicochemical parameters and microbial load were evaluated at 4 °C over 22 days of storage. The films reduced weight loss and water activity compared to fresh and treated samples (HPP and cooking). Results showed that microbial load (total aerobic mesophilic, lactic acid bacteria and total coliform) of the trout fillets covered with chitosan films was lower than that for HPP-treated samples, and similar to cooked samples, except for coliform counts.

CONCLUSION

The use of 20 g kg(-1) CEO-chitosan films showed a further improvement in the shelf-life of trout fillets when compared to that obtained with HPP and cooking treatment.

Physical Properties, Antioxidant and Antimicrobial Activity of Chitosan Films Containing Carvacrol and Pomegranate Peel Extract

Chitosan-based active films were developed by incorporation of carvacrol (10 g/L), pomegranate peel extract (PPE, 10 g/L) and carvacrol + PPE (10 g/L of each) and their physical, antioxidant and antimicrobial properties were investigated. Incorporation of carvacrol and carvacrol + PPE into the films significantly decreased the water vapor permeability, tensile strength and percentage of elongation at break. Incorporation of carvacrol, PPE and carvacrol + PPE into the films decreased the transparency, but significantly increased the total phenol content and antioxidant activity. All the films, with the exception of PPE-incorporated film, exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, the antibacterial activity against Staphylococcus aureus of the film incorporated with carvacrol + PPE was moderately higher than that incorporated with carvacrol or PPE alone, suggesting a synergistic action between carvacrol and PPE.

Preparation of gelatin films incorporated with tea polyphenol nanoparticles for enhancing controlled-release antioxidant properties

Gelatin films incorporated with chitosan nanoparticles in various free/encapsulated tea polyphenol (TP) ratios were prepared in order to investigate the influence of different ratios on the physicochemical and antioxidant properties of films. The TP-containing nanoparticles were prepared by cross-linking chitosan hydrochloride (CSH) with sulfobutyl ether-β-cyclodextrin sodium (SBE-β-CD) at three different encapsulation efficiencies (EE; ∼50%, ∼80%, and ∼100%) of TP. The stability of TP-loaded nanoparticles was maintained during the film drying process from the analysis of free TP content in the redissolved film solutions. Composite films showed no significant difference in visual aspects, while the light transmittance (250-550 nm) was decreased with incorporation of TP. Nanoparticles appeared to be homogeneously dispersed within the film matrix by microstructure analysis (SEM and AFM). TP-loaded films had ferric reducing and DPPH radical scavenging power that corresponded to the EEs. Sunflower oil packaged in bags made of gelatin films embedded with nanoparticles of 80% EE showed the best oxidation inhibitory effect, followed by 100% EE, 50% EE, and free TP, over 6 weeks of storage. However, when the gelatin film was placed over the headspace and was not in contact with the oil, the free TP showed the best effect. The results indicate that sustained release of TP in the contacting surface can ensure the protective effects, which vary with free/encapsulated mass ratios, thus improving antioxidant activities instead of increasing the dosage.

Production of an anthocyanin-rich food colourant from Thymus moroderi and its application in foods

BACKGROUND

Anthocyanins and other polyphenols from flowers and bracts of Thymus sp. are studied. An anthocyanin-rich food colourant with interesting high antioxidant activity from Thymus moroderi has been obtained, and applied to colour foods.

RESULTS

Anthocyanins and other polyphenols from T. moroderi and another five Thymus sp. were extracted in methanol/hydrochloric acid 0.1 mol L(-1) (50/50, v/v) 2 h stirring at 50 °C. They were identified and quantified by HPLC-PDA-MS and UHPLC-PDA-fluorescence, as total individual polyphenols. Total polyphenols were also determined. Flowers had higher anthocyanins and other polyphenols concentrations than bracts; for example, total polyphenols content of T. moroderi were 131.58 and 61.98 g GAE kg(-1) vegetal tissue, respectively. A liquid concentrated colourant was obtained from T. moroderi using water/citric acid as solvent. It was characterised and compared with other two commercial anthocyanin-rich food colourants from red grape skin and red carrot (colour strength of 1.7 and 3.6 AU, respectively). T. moroderi colourant had 1.2 AU colour strength, and high storage stability (>97.1% remaining colour after 110 days at 4 °C). It showed a higher polyphenols content than commercial colourants. Its antioxidant activity was 0.707 mmol Trolox eq. g(-1) plant dry weight, 69.5 times higher than red carrot. The three colourants were applied to colour yogurts, giving pinky tonalities. The colour did not change evidently (ΔE*(ab)  < 3) when stored under refrigeration during 1 month.

CONCLUSIONS

T. moroderi can be a source of anthocyanin-rich food colourant (E-163) with both high polyphenols content and high antioxidant activity. This colourant gives a stable colour to a yogurt during 1 month. These results expand the use of natural colourants.

In vitro antioxidant potential of Shemamruthaa (a herbal formulation) and its anticancer activity in the MCF-7 cell line

The current study investigates the free radical scavenging activities of methanolic and aqueous extracts of Shemamruthaa (Hibiscus rosa sinensis, Emblica officinalis and honey in definite ratio) and their anticancer activity in the breast cancer (MCF-7) cell line ex vivo.

Synthesis and characterization of zinc oxide-neem oil-chitosan bionanocomposite for food packaging application

Nano zinc oxide at different concentrations (0.1, 0.3 and 0.5%) and neem essential oil were incorporated into the chitosan polymer by solution cast method to enhance the properties of the bionanocomposite film. The functional groups, crystalline particle size, thermal stability and morphology were determined using FTIR, XRD, TGA and SEM, respectively. The results showed that 0.5% nano zinc oxide incorporated composite film have improved tensile strength, elongation, film thickness, film transparency and decreased water solubility, swelling and barrier properties due to the presence of neem oil and nano zinc oxide in the polymer matrix. Further antibacterial activity by well diffusion assay method was followed against Escherichia coli which were found to have good inhibition effect. In addition to this food quality application were carried against carrot and compared with the commercial film.