Modification of Nanocrystalline Cellulose for Bioactive Loaded Films

Despite the use of petrochemical derived packaging, many problems such as browning and food spoilage still happen in food after harvesting. There is an increasing consumers concern for food shelf life to be extended as much as possible along with a big interest in green and bioactive materials, that could be used in direct contact with aliments. In order to reach public demand, biopolymers coming from natural sources such as plants or animals have been used to replace synthetic materials. Even though natural polymers are biodegradable, they do not reach regulations required with respect to mechanical properties in commercial applications. However, the mechanical properties can be improved when reinforced with nanoparticles. Several reinforcing nanoparticules such as clays, silica or silver have been used for industrial applications, but cellulose nanocrystals (CNCs) are a better choice for food industry due to their biodegradable and biocompatible nature as well as their outstanding potential in improving mechanical and barrier properties of nanocomposites. CNCs consist of anhydroglucopyranose units (AGU) linked together and several functional hydroxyl groups found on its surface. Modifications of the CNC surface chemistry can give to cellulose new functionalities that open the way to the development of new bioactive reinforcement in food packaging. The present review will be focused on covalent and non covalent modifications that can be achieved on surface CNC with the aim of adding functionalities to be applied for food industry

Antioxidant properties of green tea polyphenols encapsulated in caseinate beads

An error occurred in the list of authors of the article: Dehkharghanian M., Lacroix M. and Vijayalakshmi M.A., Antioxidant properties of green tea polyphenols encapsulated in caseinate beads, Dairy Sci. Technol. 89 (2009) 485–499. Therefore the correct reference of the article is: Dehkharghanian M., Salmieri S., Lacroix M. and Vijayalakshmi M.A., Antioxidant properties of green tea polyphenols encapsulated in caseinate beads, Dairy Sci. Technol. 89 (2009) 485–499

Effect of the optimized selective enrichment medium on the expression of the p60 protein used as Listeria monocytogenes antigen in specific sandwich ELISA

International audienceThis paper presents the effects of the composition of different media (i.e., Tryptic soy broth (TSB), Brain heart infusion (BHI), Listeria enrichment broth (LEB), Fraser broth (FB) and University of Vermont medium (UVM)) on the detection of a short peptide fragment PepD specific to the p60 protein (p60) of L. monocytogenes by a monoclonal antibody (anti-PepD mAb). Expression of the p60 obtained was demonstrated to be proportional to the cellular growth of Listeria monocytogenes regardless of the tested growth medium. However, the early growth of L. monocytogenes and the expression of the p60 were negatively affected by the presence of selective agents present in LEB, FB and UVM. Among those three selective enrichment media commonly used for L. monocytogenes, LEB allowed a better expression of L. monocytogenes p60 after an incubation period of 18 h. Optimization of the LEB revealed that the dextrose concentration was the critical factor for improving the expression of p60 and promotes the early expression of p60. Moreover, an optimal dextrose concentration of 0.5% (w/v) in LEB, coupled with anti-PepD mAb immobilized to solid support, reduced the detection of p60 from 18 h to 9 h for an initial concentration of L. monocytogenes of 108 CFU/ml

Evaluation of antibacterial activity of branched quaternary ammonium grafted green polymers

International audienceThis study describes the antibacterial activity evaluation of film-shaped polymers based on biodegradable chains of polylactic acid (PLA), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) in branched structures with quaternary ammonium pendant groups. The materials were tested against both Gram-negative (Escherichia coli and Salmonella Typhimurium) and Gram-positive (Listeria monocytogenes) bacteria. Minimal inhibitory and maximal tolerated concentrations of the quaternary ammonium monomers were first determined. Films of pure quaternary ammonium functionalized polymers (QAFPs) and of blends of QAFPs with commercial matrices were studied to determine their inhibition effects and their bactericidal activity. A high antibacterial activity was found, up to 5.6 log, 4.4 log, and 4.2 log CFU.mL-1 reduction for respectively Escherichia coli (Salmonella Typhimurium and Listeria monocytogenes after only one hour of bactericidal tests, 6.7 log, 5.2 log and 4.9 log CFU.mL−1 reduction was observed for the respectively cited bacteria after 24 h, making these materials potentially applicable in many fields

Genipin cross-linked nanocomposite films for the immobilization of antimicrobial agent.

International audienceCellulose nanocrystal (CNC) reinforced chitosan based antimicrobial films were prepared by immobilizing nisin on the surface of the films. Nanocomposite films containing 18.65 μg/cm(2) of nisin reduced the count of L. monocytogenes by 6.73 log CFU/g, compared to the control meat samples (8.54 log CFU/g) during storage at 4 °C in a Ready-To-Eat (RTE) meat system. Film formulations containing 9.33 μg/cm(2) of nisin increased the lag phase of L. monocytogenes on meat by more than 21 days, whereas formulations with 18.65 μg/cm(2) completely inhibited the growth of L. monocytogenes during storage. Genipin was used to cross-link and protect the activity of nisin during storage. Nanocomposite films cross-linked with 0.05% w/v genipin exhibited the highest bioactivity (10.89 μg/cm(2)) during the storage experiment, as compared to that of the un-cross-linked films (7.23 μg/cm(2)). Genipin cross-linked films were able to reduce the growth rate of L. monocytogenes on ham samples by 21% as compared to the un-cross-linked films. Spectroscopic analysis confirmed the formation of genipin-nisin-chitosan heterocyclic cross-linked network. Genipin cross-linked films also improved the swelling, water solubility, and mechanical properties of the nanocomposite films

Antimicrobial effects of modified chitosan based coating containing nanoemulsion of essential oils, modified atmosphere packaging and gamma irradiation against Escherichia coli O157:H7 and Salmonella Typhimurium on green beans

The antibacterial activity of modified chitosan-based coatings containing nanoemulsion of essential oils (EOs), gamma irradiation, modified atmosphere packaging (MAP), alone or in combinations, against Escherichia coli O157:H7 and Salmonella Typhimurium was evaluated on inoculated green bean samples. Firstly, four different nanoemulsions, made of carvacrol, mandarin, bergamot and lemon Eos, respectively, were compared in terms of minimum inhibitory concentration (MIC) against the two bacteria evaluated in vitro using the micro-broth dilution method. Carvacrol nanoemulsion resulted to be the most effective antibacterial agent and was therefore selected to be incorporated into modified chitosan (MC) to form a bioactive coating. Secondly, the radiosensitivity of E. coli and S. Typhimurium to gamma irradiation was evaluated on inoculated green beans after coating deposition and MAP. Results showed that, without MAP, MC-based coating containing carvacrol nanoemulsion significantly increased the radiosensitization of E. coli and S. Typhimurium by 1.32-fold and 1.30-fold, respectively. Remarkably, the use of bioactive coating under MAP caused a synergistic effect with an increase in radiosensitivity by 1.80-fold and 1.89-fold for E. coli and S. Typhimurium, respectively. Thirdly, the antibacterial effects of the antimicrobial coating, gamma irradiation, MAP alone and their combinations were evaluated against these two bacteria during a 13-days storage of green beans at 4 degrees C. Bioactive coating deposition or gamma irradiation treatment resulted effective in controlling the growth of the two bacteria during the entire shelf-life. Moreover, it was also found that the combined treatment of antimicrobial coating, gamma irradiation and MAP caused the reduction of microbial population to undetectable levels during the whole storage period for E. coli and from day 7 to the end of storage for S. Typhimurium. The obtained results can be interested to food companies aiming to ensure the food safety with a prolonged shelf life

Antifungal activities of combined treatments of irradiation and essential oils (EOs) encapsulated chitosan nanocomposite films in in vitro and in situ conditions

International audienceCellulose nanocrystals (CNCs) reinforced chitosan based antifungal films were prepared by encapsulating essential oils (EOs) nanoemulsion. Vapor phase assays of the chitosan-based nanocomposite films loaded with thyme-oregano, thyme-tea tree and thyme-peppermint EO mixtures showed significant antifungal activity against Aspergillus niger, Aspergillus flavus, Aspergillus parasiticus, and Penicillium chrysogenum, reducing their growth by 51-77%. Combining the bioactive chitosan films loaded with thyme and oregano EOs produced ~2 log reduction in fungal growth in inoculated rice during 8 weeks of storage at 28 °C. The bioactive films showed a slow release (26%) of volatile components over 12 weeks of storage. Sensorial evaluation of rice samples packed with the bioactive films showed no significant change in odor, taste, color and general appreciation compared with untreated rice. Incorporation of cellulose nanocrystals (CNCs) with the chitosan matrix played an important role in stabilizing the physicochemical and release properties of the nanocomposite films. In addition, combining the bioactive chitosan films with a dose of 750 Gy of ionizing radiation showed significantly higher antifungal and mechanical properties than treatment with the bioactive film or irradiation alone