Citric acid incorporated in a chitosan film as an active packaging material to improve the quality and duration of matured cheese shelf life.

Chitosan-based film incorporated with citric acid was prepared by the casting method for application in a Brazilian matured cheese. Three formulations of cheese were processed, with the intention of evaluating the application of a starter culture and the effect of the film in terms of its physiochemical, microbiological, and sensorial characteristics. It was observed by scanning electron microscopy (sem) analysis that the film has a homogeneous appearance, and the crosslinking between citric acid and chitosan was confirmed by the Fourier transform infrared spectroscopy (FTIR) analysis. The cheese with chitosan-based film presented lower weight loss (5.2%) and showed antimicrobial activity against aerobic mesophilic bacteria. All samples showed high rates of sensorial acceptability (>79%), with no significant differences between them. It is apparent that the chitosan film maintained the typical cheese characteristics. Therefore, chitosan and citric acid film can be used to improve the characteristics of matured cheese and extend its shelf life.

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.

Cytotoxic and genotoxic effects of silver nanoparticle/carboxymethyl cellulose on Allium cepa.

Several mutagenic agents may be present in substances released in the environment, which may cause serious environmental impacts. Among these substances, there is a special concern regarding the widespread use of silver nanoparticles (AgNP) in several products due to their widely known bactericidal properties, including in the medical field and the food industry (e.g., active packaging). The assessment of the effects of AgNP released in the environment, having different concentrations, sizes, and being associated or not to other types of materials, including polymers, is therefore essential. In this research, the objective was to evaluate the genotoxic and cytotoxic effects of AgNP (size range between 2 and 8 nm) on root meristematic cells of Allium cepa (A. cepa). Tests were carried out in the presence of colloidal solution of AgNP and AgNP mixed with carboxymethylcellulose (CMC), using distinct concentrations of AgNP. As a result, when compared to control samples, AgNP induced a mitotic index decrease and an increase of chromosomal aberration number for two studied concentrations. When AgNP was in the presence of CMC, no cytotoxic potential was verified, but only the genotoxic potential for AgNP dispersion having concentration of 12.4 ppm.

New Edible Bionanocomposite Prepared by Pectin and Clove Essential Oil Nanoemulsions.

Nanocomposites are being extremely investigated to provide packaging with interesting characteristics for packages. Because of essential oils' natural occurrence and antibacterial activity, they are considered as an alternative for synthetic additives in the food industry. In this paper, we studied an edible bionanocomposite film made up of pectin and clove essential oil nanoemulsion for application as edible package. Mechanical properties, water vapor permeability (WVP), and antibacterial activity were analyzed. From mechanical and WVP analyses, we noticed an interesting improvement in film properties. In the antibacterial activity test, disk diffusion was used to assess the inhibition zones of Escherichia coli and Staphylococcus aureus. With these results, we concluded that the most interesting results were promoted by smaller nanodroplets (diameter of approximately 142 nm).

Combining Chitosan Nanoparticles and Garlic Essential Oil as Additive Fillers to Produce Pectin-Based Nanocomposite Edible Films.

Edible films were produced by combining a pectin (PEC) matrix with chitosan nanopar-ticle (CSNP), polysorbate 80 (T80), and garlic essential oil (GEO) as an antimicrobial agent. CSNPs were analyzed for their size and stability, and the films, throughout their contact angle, scanning electron microscopy (SEM), mechanical and thermal properties, water vapor transmission rate, and antimicrobial activity. Four filming-forming suspensions were investigated: PGEO (control); PGEO@T80; PGEO@CSNP; PGEO@T80@CSNP. The compositions are included in the methodology. The average particle size was 317 nm, with the zeta potential reaching +21.4 mV, which indicated colloidal stability. The contact angle of the films exhibited values of 65°, 43°, 78°, and 64°, respec-tively. These values showed films with variations in hydrophilicity. In antimicrobial tests, the films containing GEO showed inhibition only by contact for S. aureus. For E. coli, the inhibition occurred in films containing CSNP and by direct contact in the culture. The results indicate a promising al-ternative for designing stable antimicrobial nanoparticles for application in novel food packaging. Although, it still shows some deficiencies in the mechanical properties, as demonstrated in the elongation data.

Chelating and antibacterial properties of chitosan nanoparticles on dentin.

OBJECTIVES: The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin. MATERIALS AND METHODS: One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups. RESULTS: The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPs-treated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05). CONCLUSIONS: CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.

Evaluation of the genotoxicity of chitosan nanoparticles for use in food packaging films.

The use of nanoparticles in food packaging has been proposed on the basis that it could improve protection of foods by, for example, reducing permeation of gases, minimizing odor loss, and increasing mechanical strength and thermal stability. Consequently, the impacts of such nanoparticles on organisms and on the environment need to be investigated to ensure their safe use. In an earlier study, Moura and others (2008a) described the effect of addition of chitosan (CS) and poly(methacrylic acid) (PMAA) nanoparticles on the mechanical properties, water vapor, and oxygen permeability of hydroxypropyl methylcellulose films used in food packaging. Here, the genotoxicity of different polymeric CS/PMAA nanoparticles (size 60, 82, and 111 nm) was evaluated at different concentration levels, using the Allium cepa chromosome damage test as well as cytogenetic tests employing human lymphocyte cultures. Test substrates were exposed to solutions containing nanoparticles at polymer mass concentrations of 1.8, 18, and 180 mg/L. Results showed no evidence of DNA damage caused by the nanoparticles (no significant numerical or structural changes were observed), however the 82 and 111 nm nanoparticles reduced mitotic index values at the highest concentration tested (180 mg/L), indicating that the nanoparticles were toxic to the cells used at this concentration. In the case of the 60 nm CS/PMAA nanoparticles, no significant changes in the mitotic index were observed at the concentration levels tested, indicating that these particles were not toxic. The techniques used show promising potential for application in tests of nanoparticle safety envisaging the future use of these materials in food packaging.