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1.
Front Chem ; 10: 926364, 2022.
Article in English | MEDLINE | ID: mdl-35958229

ABSTRACT

Chitosan-based hybrid nanocomposites, containing cellulose nanocrystals (CNCs), graphene oxide (GO), and borate as crosslinking agents, were successfully prepared by solution-casting technique. The synergistic effect of the two fillers, and the role of the cross-linker, in enhancing the structural and functional properties of the chitosan polymer, was investigated. XPS results confirm the chemical interaction between borate ions and hydroxyl groups of chitosan, GO, and CNCs. The morphological characterization shows that the GO sheets are oriented along the casting surface, whereas the CNC particles are homogenously distributed in the sample. Results of tensile tests reveal that the presence of graphene oxide enhances the elastic modulus, tensile strength, elongation at break, and toughness of chitosan, while cellulose and borate induce an increase in the elastic modulus and stress at the yield point. In particular, the borate-crosslinked chitosan-based sample containing 0.5 wt% of GO and 0.5 wt% of CNCs shows an elongation at a break value of 30.2% and a toughness value of 988 J*m-3 which are improved by 124% and 216%, respectively, compared with the pristine chitosan. Moreover, the water permeability results show that the presence of graphene oxide slightly increases the water barrier properties, whereas the borate and cellulose nanocrystals significantly reduce the water vapor permeability of the polymer by about 50%. Thus, by modulating the content of the two reinforcing fillers, it is possible to obtain chitosan-based nanocomposites with enhanced mechanical and water barrier properties which can be potentially used in various applications such as food and electronic packaging.

2.
Carbohydr Polym ; 231: 115772, 2020 Mar 01.
Article in English | MEDLINE | ID: mdl-31888830

ABSTRACT

Cystalline-Cc and ultra-milled Amorphous-Ca cellulose were used as reactive filler to tune the performances of composite polyurethane-cellulose-foams, PUC. The effect of Cc and Ca on chemo-physical and mechanical properties of PUC was analysed through FTIR, morphological analysis, thermal conductivity and compression measurements. FTIR results show that, both Cc and Ca react with isocyanate through the OH functional groups contributing to the formation of a tough cellulose-polyurethane network. Morphological observations show that the addition of both Cc and Ca induces a decrease of average cell-size compared to the pristine-PU, thus confirming that they act as nucleating agent. In addition, the better dispersion of the Ca in the polyol, with respect to Cc induces, a finer cell leading to a reduction of the thermal conductivity around 33 % (for the composite loaded with 20 %wt-Ca) with respect to pristine-PU. Finally, the addition of Ca highly reactive modifies the mechanical behaviour from rigid-brittle to semi-rigid.

3.
Carbohydr Polym ; 211: 195-203, 2019 May 01.
Article in English | MEDLINE | ID: mdl-30824079

ABSTRACT

Chitosan (CS) aerogels were prepared by freeze-drying as potential adsorbents for water purification, and the effect of the strategy of crosslinking was investigated by varying the amount of crosslinker (glutaraldehyde) and the sequence of steps for the preparation of the aerogel. Two procedures were compared, in which the crosslinking step was carried out before or after the freeze-drying of the starting CS solution. When crosslinking was postponed after the freeze-drying step, the adsorption capacity towards an anionic dye, such as indigo carmine, considerably increased (up to +45%), reaching values as high as 534.4 ± 30.5 mg g-1. The same crosslinking strategy ensured a comparable improvement also in nanocomposite aerogels containing graphene oxide (GO), which was added to enhance the mechanical strength and provide adsorption capacity towards cationic dyes. Besides possessing good mechanical strength (compressive modulus higher than 1 MPa), the CS/GO aerogels were able to bind also cationic pollutants such as methylene blue. The maximum uptake capacity increased from 4.3 ± 1.6 to 168.6 ± 9.6 mg of cationic dye adsorbed per gram of adsorbent with respect to pristine CS aerogels.

4.
Carbohydr Polym ; 102: 385-92, 2014 Feb 15.
Article in English | MEDLINE | ID: mdl-24507295

ABSTRACT

Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na(+) ions of natural montmorillonite with silver ions. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the achievement of the intercalation of chitosan into the silicate galleries of montomorillonite as well as the interaction between chitosan and Ag ions and silver particles lead to an enhancement of the thermal stability, to an improvement of mechanical strengths and to a reduction of the liquid water uptake of the obtained bionanocomposites. Results also show that silver ions are released in a steady and prolonged manner providing, after 24 h, a significant reduction in the microbial growth of Pseudomonas spp.


Subject(s)
Chitosan/chemistry , Metal Nanoparticles/chemistry , Silver/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Microscopy, Electron, Scanning
5.
J Dairy Sci ; 94(11): 5298-304, 2011 Nov.
Article in English | MEDLINE | ID: mdl-22032352

ABSTRACT

The aim of this study was to evaluate the effects of a bio-based coating containing silver-montmorillonite nanoparticles combined with modified-atmosphere packaging (MAP) on microbial and sensory quality decay of Fior di latte cheese. Different concentrations of silver nanoparticles (0.25, 0.50, and 1.00 mg/mL) were dispersed in a sodium alginic acid solution (8% wt/vol) before coating the cheese. Modified-atmosphere packaging was made up of 30% CO(2), 5% O(2), and 65% N(2). The combination of silver-based nanocomposite coating and MAP enhanced Fior di latte cheese shelf life. In particular, product stored in the traditional packaging showed a shelf life of about 3 d, whereas coated cheese stored under MAP reached a shelf life of more than 5 d, regardless of the concentration of silver nanoparticles. The synergistic effects between antimicrobial nanoparticles and initial headspace conditions in the package could allow diffusion of dairy products beyond the local area.


Subject(s)
Bentonite/analysis , Cheese/standards , Food Packaging/methods , Metal Nanoparticles/analysis , Silver/analysis , Cheese/analysis , Cheese/microbiology , Food Microbiology , Humans , Taste , Time Factors
6.
Int J Food Microbiol ; 148(3): 164-7, 2011 Aug 15.
Article in English | MEDLINE | ID: mdl-21684619

ABSTRACT

In this work, silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles have been obtained by allowing silver ions from nitrate solutions to replace the Na(+) of natural montmorillonite and then to be reduced by a thermal treatment. Ag-MMT were used as active antimicrobial compounds to improve the shelf life of fresh fruit salad. In order to assess their influence on product shelf life, sensorial and microbiological quality has been monitored during the storage. The microbiological quality was determined by monitoring the principal spoilage microorganisms (mesophilic and psychrotrophic bacteria, coliforms, lactic acid bacteria, yeasts and molds). Additionally, the evolution of sensorial quality was assessed by monitoring color, odor, firmness and product overall quality. The Ag-MMT nanoparticles seemed to be effective in inhibiting microbial growth, above all at the highest tested concentration. Consequently, the sensorial quality of samples stored in the active packaging appeared to be better preserved. Thus, experimental results showed that a significant shelf life prolongation of fresh fruit salad can be obtained by a straightforward new packaging system.


Subject(s)
Anti-Infective Agents/chemistry , Bentonite/chemistry , Food Preservation/methods , Fruit/microbiology , Silver/chemistry , Bacteria/drug effects , Bacteria/growth & development , Fungi/drug effects , Fungi/growth & development , Nanoparticles/chemistry , Yeasts/drug effects , Yeasts/growth & development
7.
J Dairy Sci ; 94(4): 1697-704, 2011 Apr.
Article in English | MEDLINE | ID: mdl-21426957

ABSTRACT

The objective of this work was to evaluate the effectiveness of an antimicrobial packaging system containing active nanoparticles on the quality deterioration of Fior di Latte cheese. To this aim, 3 concentrations of silver montmorillonite embedded in agar were used. The cell loads of spoilage and useful microorganisms were monitored during a refrigerated storage period. Moreover, cheese sensory quality (i.e., odor, color, consistency, and overall quality) was evaluated by means of a panel test. Results showed that the active packaging system markedly increased the shelf life of Fior di Latte cheese, due to the ability of silver cations to control microbial proliferation, without affecting the functional dairy microbiota and the sensory characteristics of the product. The active packaging system developed in this work could be used to prolong the shelf life of Fior di Latte and boost its distribution beyond local market borders.


Subject(s)
Cheese/microbiology , Food Preservation/methods , Metal Nanoparticles , Silver , Agar , Hydrogel, Polyethylene Glycol Dimethacrylate
8.
J Food Prot ; 73(12): 2256-62, 2010 Dec.
Article in English | MEDLINE | ID: mdl-21219745

ABSTRACT

Silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles were obtained by allowing silver ions from nitrate solutions to replace the Na(+) of natural montmorillonite and to be reduced by thermal treatment. The Ag-MMT nanoparticles were embedded in agar, zein, and poly(ε-caprolactone) polymer matrices. These nanocomposites were tested in vitro with a three-strain cocktail of Pseudomonas spp. to assess antimicrobial effectiveness. The results indicate that Ag-MMT nanoparticles embedded into agar may have antimicrobial activity against selected spoilage microorganisms. No antimicrobial effects were recorded with active zein and poly(ε-caprolactone). The water content of the polymeric matrix was the key parameter associated with antimicrobial effectiveness of this active system intended for food packaging applications.


Subject(s)
Bentonite/chemistry , Food Packaging/instrumentation , Silver/chemistry , Agar/chemistry , Chemistry, Physical , Food Packaging/methods , Food Technology/methods , Nanocomposites
9.
J Food Prot ; 71(1): 119-25, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18236671

ABSTRACT

In this study we tested the antimicrobial activity of polyethylene films modified by means of plasma processes that were followed by the chemical immobilization of lysozyme, an antimicrobial enzyme. To chemically immobilize the enzyme in its active form at the surface of polyethylene, substrates that had been plasma treated under different experimental conditions were soaked in lysozyme solutions at different concentrations. The immobilization of the enzyme was checked, and the antimicrobial activity of the films was investigated by observing the death rate of Micrococcus lysodeikticus cells suspended in phosphate buffer in contact with the films. The results clearly indicate that plasma-treated films loaded with lysozyme are active against the selected microorganism. A modified version of the Gompertz equation was used to quantitatively valuate the dependence of the antimicrobial activity of the films under both plasma treatment conditions and lysozyme concentrations.


Subject(s)
Anti-Bacterial Agents/pharmacology , Drug Packaging/methods , Food Packaging/methods , Micrococcus/physiology , Muramidase/pharmacology , Colony Count, Microbial , Consumer Product Safety , Dose-Response Relationship, Drug , Enzymes, Immobilized , Food Microbiology , Food Preservation/methods , Microbial Sensitivity Tests , Micrococcus/drug effects , Micrococcus/growth & development , Polyethylene
10.
J Food Prot ; 69(4): 866-70, 2006 Apr.
Article in English | MEDLINE | ID: mdl-16629031

ABSTRACT

A new technique for the immobilization of lysozyme onto the surface of polyvinylalcohol films is presented. The active compound was sprayed along with a suitable bonding agent onto the surface of the cross-linked polymeric matrix. Active compound release tests determined the amount of lysozyme immobilized on the film surface. With the use of Micrococcus lysodeikticus, the antimicrobial activity of the films was determined and the results correlated with the amount of immobilized lysozyme. This new technique was effective for immobilizing the enzyme, and the developed films were active against the test microorganism. Results were compared with those obtained with a different immobilizing technique, in which the active compound was bound into the bulk of the polymeric film. As expected, the surface-immobilized lysozyme films have a higher antimicrobial activity than bulk-bound films.


Subject(s)
Anti-Infective Agents/pharmacology , Drug Packaging/methods , Food Packaging/methods , Micrococcus/drug effects , Muramidase/pharmacology , Polyvinyl Alcohol , Colony Count, Microbial , Consumer Product Safety , Enzymes, Immobilized , Food Microbiology , Food Preservation/methods , Humans , Microbial Sensitivity Tests , Micrococcus/growth & development , Time Factors
11.
J Food Prot ; 67(6): 1190-4, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15222548

ABSTRACT

The suitability of antimicrobial release films made from highly swellable polymers for use in food packaging was evaluated. The possibility of modulating the release kinetics of active compounds either by regulating the degree of cross-link of the polymer matrix or by using multilayer structures was addressed. The release kinetics of lysozyme, nisin, and sodium benzoate (active compounds with different molecular weights) were determined at ambient temperature (25 degrees C). The effectiveness of the proposed active films in inhibiting microbial growth was addressed by determining the antimicrobial efficiency of the released active compounds. Micrococcus lysodeikticus, Alicyclobacillus acidoterrestris, and Saccharomyces cerevisiae were used to test the antimicrobial efficiency of released lysozyme, nisin, and sodium benzoate, respectively. Results indicate that the release kinetics of both lysozyme and nisin can be modulated through the degree of cross-link of the polymer matrix, whereas multilayer structures need to be used to control the release kinetics of sodium benzoate. All the active compounds released from the investigated active films were effective in inhibiting microbial growth.


Subject(s)
Bacillus/growth & development , Food Packaging/methods , Food Preservation/methods , Food Preservatives/pharmacology , Micrococcus/growth & development , Saccharomyces cerevisiae/growth & development , Colony Count, Microbial , Dose-Response Relationship, Drug , Food Microbiology , Kinetics , Muramidase/pharmacology , Nisin/pharmacology , Sodium Benzoate/pharmacology
12.
J Control Release ; 90(1): 97-107, 2003 Jun 05.
Article in English | MEDLINE | ID: mdl-12767710

ABSTRACT

A mathematical model able to describe the release kinetics of antimicrobial agents from crosslinked polyvinylalcohol (PVOH) into water is presented. The model was developed by taking into account the diffusion of water molecules into the polymeric film, the counter-diffusion of the incorporated antimicrobial agent from the film into water, and the polymeric matrix swelling kinetic. To validate the model the water sorption kinetics as well as the release kinetics of three antimicrobial agents (i.e., lysozyme, nisin and sodium benzoate, all approved to be used in contact with food) were determined at ambient temperature (25 degrees C). The three investigated active agents were entrapped in four films of PVOH with a different degree of crosslink. The model was successfully used to fit all the above sets of data, corroborating the validity of the hypothesis made to derive it.


Subject(s)
Anti-Bacterial Agents/chemistry , Food Packaging/methods , Polyvinyl Alcohol/chemistry , Algorithms , Chromatography, High Pressure Liquid , Food Microbiology , Kinetics , Models, Chemical , Muramidase/chemistry , Nisin/chemistry , Sodium Benzoate/chemistry , Time Factors , Water
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