Véronique Coma

Bioactive packaging technologies for extended shelf life of meat-based products

To prevent the development and spread of spoilage and pathogenic microorganisms via meat foodstuffs, antimicrobial packaging materials could be a potential alternative solution. Instead of mixing antimicrobial compounds directly with food, incorporating them in films allows the functional effect at the food surface - where the microbial growth is mostly found - to be localized. Antimicrobial packagings include systems such as adding a sachet into the package, dispersing bioactive agents in the packaging, coating bioactive agents on the surface of the packaging material, or utilizing antimicrobial macromolecules with film forming properties or edible matrices. The potential of these technologies are evaluated for the preservation of meat and meat products.

Active edible polysaccharide coating and interactions between solution coating compounds

To control pathogenic strain growth on food surface, anti-microbial edible coatings were obtained from hydroxy propyl methyl cellulose associated with nisin. The inhibitory activity of nisin was confirmed on Listeria innocua and Staphylococcus aureus. To improve packaging moisture barrier properties, stearic acid (SA) was used, but preliminary experiments showed a decrease in the inhibitory activity of coatings, probably from electrostatic interactions with the bacteriocin. The study of interactions between both the compounds was then conducted to subsequently optimize nisin desorption. First, the negatively charged carboxyl groups of SA were confirmed by trapping cationic ion method, allowing electrostatic interactions. Secondly, a comparative study of nisin fixation in SA or methyl stearate showed that SA–nisin interactions were mainly electrostatic. Finally, calcium ion addition to the nisin–SA mixture showed a potential application in order to improve packaging activity by increasing nisin desorption from coatings.

Photodegradation and Biodegradation Study of a Starch and Poly(Lactic Acid) Coextruded Material

To simulate the behavior of agricultural mulch coextruded poly(lactic acid)(PLA)/starch films, two stages were carried out. The first was an ultraviolet treatment (UV) at 315 nm, during which glass transition temperature Tg, weight, and molecular weight (MW) decreased and a separation between PLA and starch phase was observed. For the second stage, the mineralization of the carbon of the material was followed using the ASTM (D 5209–92 and 5338–92) and ISO/CEN (14852 and 14855) standard procedures. To measure the biodegradability of polymer material, the assessment of the carbon balance allowed determination of the distribution between the carbon rate used to the biomass synthesis or the respiration process (released CO2), as well as the dissolved organic carbon into the culture medium and the carbon in the residual insoluble material. The influence of the nature of the medium and the standardized procedures on the final rate of biodegradation was investigated. Whatever the standardized method, the biodegradation percentage was significantly stronger in liquid medium (92.4–93.4) than on inert medium (80–83%). In the case of the compost process, only released CO2 was measured and corresponded to 79.1–80.3%.

Preparation and characterization of active emulsified films based on chitosan-carboxymethyl cellulose containing zinc oxide nano particles

Active nanocomposites based on carboxymethyl cellulose-chitosan-oleic acid (CMC-CH-OL) incorporated with different concentrations (0.5-2wt.%) of zinc oxide nanoparticles (ZnO NPs) were produced by casting method. The effects of ZnO NPs on the morphological, mechanical, thermal, physical and antifungal properties of the films were studied. New interaction between ZnO NPs and polymer matrix were confirmed by Fourier Transform infrared. After addition of ZnO NPs, tensile strength, lightness (L*) and thermal stability decreased however, elongation at break, contact angle, a* (greenness) and b* (yellowness) of the nanocomposite films increased in comparison to the films without nano-filler. UV transmittance at 280nm decreased from 17.3% to 0.2, 0.1 and 0.1 for the nanocomposite films containing 0.5, 1 and 2wt.% ZnO NPs, respectively, suggesting higher UV blocking properties. Disc diffusion test showed considerable antifungal properties of the active nanocomposite films against Aspergillus niger, especially in CMC-CH-OL-ZnO 2wt.% by more than 40% fungal growth inhibition.

Synthesis and Antibacterial Activity of Aminodeoxyglucose Derivatives against Listeria innocua and Salmonella typhimurium

In this study aminodeoxyglucose derivatives were synthesized and evaluated for their antibacterial activity against two food bacteria, Listeria innocua and Salmonella typhimurium . 6-Amino-6-deoxy-alpha-D-methylglucopyranose (GSA-6), 3-amino-3-deoxy-D-glucopyranoside (GSA-3), and beta-D-glucopyranosylamine (GSA-1) were synthesized and concurrently tested with commercially available D-glucosamine (GSA-2) for antibacterial activity. Results obtained from this study showed a pronounced antagonist effect due to the position of amino groups of aminoglucose derivatives on the antibacterial activity. GSA-3 was the most active compound. At a concentration of 2 x 10(-4) mol mL(-1), it delayed the growth of both bacteria with percentages of inhibition of 29 and 15% for L. innocua and S. typhimurium, respectively. At the same concentration the percentages of inhibition for other aminodeoxyglucoses varied between 5 and 18% and between 2 and 11% for L. innocua and S. typhimurium, respectively. All compounds were characterized by FTIR, (1)H NMR, and (13)C NMR spectroscopy.

Synthesis and evaluation of N-alkyl-β-d-glucosylamines on the growth of two wood fungi, Coriolus versicolor and Poria placenta

Various glucosylamines were synthesized from glucose and different alkyl amine compounds. These amino compounds are beta-D-glucopyranosylamine (GPA), N-ethyl-beta-D-glucopyranosylamine (EtGPA), N-butyl-beta-D-glucopyranosylamine (BuGPA), N-hexyl-beta-D-glucopyranosylamine (HeGPA), N-octyl-beta-D-glucopyranosylamine (OcGPA), N-dodecyl-beta-D-glucopyranosylamine (DoGPA), N-(2-hydroxyethyl)-beta-D-glucopyranosylamine (HEtGPA) and N,N-di(2-hydroxyethyl)-beta-D-glucopyranosylamine (DHEtGPA). They were tested for their antifungal activity against the growth of Coriolus versicolor and Poria placenta. An improvement of the antifungal activity with the increase of alkyl chain length was observed. DoGPA exhibited the best antifungal activity against both strains. It completely inhibited the fungal growth at 0.01x10(-3)molmL(-1) and 0.0075x10(-3)molmL(-1) for C. versicolor and P. placenta, respectively. For other glucosylamines higher concentrations were needed for complete inhibition of fungi.

Active naringin-chitosan films: impact of UV irradiation.

Bioactive citrus extract-chitosan films were prepared through solvent casting-evaporation method. The impact of near UV irradiation was studied to reach a better understanding of the film behavior. The antimicrobial activity of films against Listeria innocua was maintained after UV irradiation. To study the interaction between chitosan and citrus extract components, naringin (main component) was selected as the model compound. UV treatment caused modifications of the flavanone regardless of the solvent used for its dissolution, depending on the concentration of naringin in the film: the greater the concentration the lower the modification. DSC results suggested cross-links due to UV irradiation and interactions between naringin and chitosan. This was confirmed by a decrease in the naringin release from the irradiated samples. Naringin- and citrus extract-chitosan films showed an increased absorbance in the UV region compared to pure chitosan films, showing potentiality for decreasing the lipid oxidation induced by UV light in foodstuffs.

In vitro inhibitory effect of tetrahydrocurcuminoids on Fusarium proliferatum growth and fumonisin B1 biosynthesis

Many plant pathogens produce toxic metabolites when growing on food and feed. Some antioxidative components seem to prevent fungal growth and mycotoxin formation. Recently, we synthesized a new class of powerful antioxidative compounds, i.e. tetrahydrocurcuminoids, and its structure/antioxidant activity relationships have been established. The South West of France produces large amounts of corn, which can be infected by Fusarium species, particularly F. proliferatum. In this context, the efficiency of tetrahydrocurcuminoids, which can be obtained from natural curcuminoids, was investigated to control in vitro the growth of F. proliferatum and the production of its associated mycotoxin, fumonisin B1. The relation between structure and antifungal activity was studied. Tetrahydrocurcumin (THC1), with two guaiacyl phenolic subunits, showed the highest inhibitory activity (measured as radial growth on agar medium) against the F. proliferatum development (67% inhibition at a concentration of 13.6 µmol ml−1). The efficiencies of THC2 (36% at a concentration of 11.5 µmol ml−1), which contains syringyl phenolic units, and THC3 (30% at a concentration of 13.6 µmol ml−1), which does not have any substituent on the aromatic rings, were relatively close. These results indicate that the simultaneous presence of guaiacyl phenols and the enolic function of the β-diketone moiety play an important role in the inhibition mechanisms. The importance of this combination was confirmed using n-propylguaiacol and acetylacetone as molecular models. Under the same conditions, ferulic acid and eugenol, other natural phenolic antioxidants, were less efficient in inhibiting fungal growth. THC1 also reduced fumonisin B1 production in liquid medium by approximately 35, 50 and 75% at concentrations of 0.8, 1.3, and 1.9 µmol ml−1, respectively. These very low inhibitory concentrations show that tetrahydrocurcuminoids could be one of the most promising biobased molecules for the control of mycotoxinogen fungal strains.

The use of lysozyme to prepare biologically active chitooligomers

Two types of crustacean commercial chitosans (CS1, CS2) were dissolved in lactic acid solutions, hydrolysed by lysozyme and finally fractioned by methanol solutions into two parts containing chito-oligomers (CS-O1, CS-O2). The antioxidant power and antimicrobial properties of both fractions were studied and compared with non-hydrolysed CS1 and CS2. The antioxidant properties were determined by the ferric ion reducing antioxidant power (FRAP) method while the bioactive properties were evaluated against a strain of Listeria monocytogenes. CS-O obtained from the solid fraction of the chito-oligomers solid fractions treated with 90% methanol showed the highest reducing power. Microbiological tests showed that CS-O exhibit higher antilisterial activity than CS.

Influence of the variation of the alkyl chain length of N-alkyl-β-D-glycosylamine derivatives on antifungal properties.

Twelve new glucosidic and galactosidic derivatives of N-alkylaminosugars with different alkylamines from 6 to 18 carbons were synthesized and characterized by (1)H and (13)C NMR. Their antifungal activity against the food fungal pathogen Aspergillus niger was evaluated using the radial growth assay. The influence of the variation of the alkyl chain length of N-alkylaminosugars on the mycelium growth was then discussed. Inhibition by the different alkylamines is shown as a biostatic effect rather than a biocidal effect. It was observed that alkylamines keep their antifungal properties after a thermal treatment compatible with food packaging and processing.