Development of cellulosenanocrystal reinforcedantimicrobial nanocomposite filmsfor food packaging application
Bibliographic record
Abstract
Au cours des dernieres annees, il y a eu une formidable expansion de l'evolution de la recherche et de la technologie dans le domaine de la nanotechnologie, ce qui a entraine des developpements significatifs et des applications dans les domaines de l'alimentation et de l'agriculture. En particulier, le domaine de l'emballage alimentaire represente un domaine prometteur et excitant pour l'utilisation de la nanotechnologie. La cellulose nanocrystalline (CNC), qui est produite a partir du bois, represente une occasion en or pour les vastes ressources forestieres du Canada. Des essais toxicologiques ont egalement montre que la CNC est moins dommageable pour l'environnement que les autres nanomateriaux et sans effets toxiques. Cette these porte sur l'utilisation de la CNC pour le developpement de nouveaux materiaux, respectueux de l'environnement, tels des films bionanocomposites antimicrobiens pour l'application dans l'emballage alimentaire. Le chitosane, un polymere naturel, non toxique, biocompatible et biodegradable, a ete choisi comme matrice pour la fabrication de films bionanocomposites. Des films de chitosane bionanocomposite renforces par la CNC ont ete fabriques par un procede a partir de solutions et on a constate que la CNC a agi comme un bon agent de renforcement dans le chitosane. L’incorporation de CNC a ameliore la resistance mecanique, la transmission de la vapeur d'eau, la permeabilite et les proprietes de gonflement des films de chitosane. La concentration optimale CNC est de 5% pds/ pds de chitosane. Apres la mise au point d'une formulation de chitosane /CNC optimisee, l’attention a ete deplacee vers le developpement de films bionanocomposite capables d'inhiber la croissance, a la surface, de bacteries pathogenes dans les produits carnes. La nisine, un agent antimicrobien naturel, a ete immobilise a la surface des films de chitosane/CNC a l'aide de la genipine. Les films antimicrobiens developpes ont inhibe avec succes la croissance de L. monocytogenes dans des echantillons de viande prete-a-manger (PAM). Une faible concentration de reticulation de genipin (0,05% pds/v) a protege de l'activite antimicrobienne des films dans un etat de stockage extreme. La resistance a l'eau et la resistance mecanique des films ont egalement augmente en raison de la reticulation de la genipine. La spectroscopie a transformee de Fourier (FTIR) a ete effectuee pour etudier les changements dans les bandes infrarouges lies a la reticulation du film par la genipine. La microfluidization, qui est une technique d'homogeneisation a haute pression, a ete utilise pour distribuer de maniere homogene au sein de la matrice de chitosane la CNC et de developper des films bionanocomposites de resistance elevee. Une methodologie statistique, dite de ‘surface de reponse’ (RSM), a ete adoptee pour optimiser systematiquement le contenu en CNC, la pression de la microfluidisation et le nombre de cycles de microfluidisation pour optimiser la resistance mecanique des films de chitosane/CNC. La microscopie electronique a balayage (MEB) des films microfluidisees chitosane/CNC a revele une reduction de 10 a 15 fois dans la taille des agregats par rapport aux films de chitosane/CNC non microfluidise. La RSM a egalement ete utilisee pour optimiser une nouvelle formulation capable d'inhiber les bacteries gramme-negatives (E. coli et S. typhimurium) et les bacteries a Gramme-positives (L. monocytogenes). Une concentration de nisine de 125 a 150 μg/mL avec un ethylenediaminetetraacetate disodique (Na -EDTA) concentration de 20 a 30 mM et un pH de 5- 6 a inhibe l'ensemble des trois bacteries. La formulation antimicrobienne developpee a ete immobilisee sur la surface des films de chitosane /CNC microfluidisees par la genipine par reticulation. L’rradiation gamma a faible dose a ete appliquee sur les films. On a constate chez les films prepares par la combinaison de la reticulation de genipine et l’irradiation gamma (1,5 kGy), la plus haute activite antimicrobienne in vitro contre E. coli et Listeria monocytogenes a la fin de 35 jours de stockage. Les films ont augmente la duree de vie de la viande de porc frais de plus de 5 semaines et ont aussi inhibe la croissance de bacteries pathogenes dans des echantillons de viande. Abstract In recent years there is a tremendous expansion of research and technology developments in the field of nanotechnology, which resulted in significant application developments in the food and agriculture areas. Particularly, the field of food packaging represents a promising and exciting field for the use of nanotechnology. Cellulose nanocrystals (CNC), which are produced from wood, represent a glorious opportunity for Canada’s vast forest resources. Toxicological experiments have also shown CNC to be far more environmentally benign than other nanomaterials. This thesis examines the use of CNC for the development of novel, environment friendly, antimicrobial bionanocomposite films for food packaging application. Chitosan, a natural, non-toxic, biodegradable, biocompatible polymer was chosen as the matrix for the fabrication of bionanocomposite films. CNC reinforced chitosan based bionanocomposite films were fabricated by solution casting method and it was found that CNC acted as a good reinforcing agent in chitosan. CNC incorporation improved the mechanical strength, water vapor permeability and swelling property of the chitosan films. The optimum CNC concentration was found to be 5% w/w of chitosan. After the development of an optimized chitosan/CNC formulation, the focus was shifted to the development of bionanocomposite films capable of inhibiting surface growth of pathogenic bacteria in meat products. Nisin, a natural antimicrobial agent, was immobilized on the surface of the CNC/chitosan films by using genipin as a cross-linking agent. The developed antimicrobial films successfully inhibited the growth of L. monocytogenes in ready-to-eat (RTE) meat samples. Low concentration of genipin cross-linking (0.05% w/v) protected the antimicrobial activity of the films in extreme storage condition. Water resistance and mechanical strength of the films also increased due to genipin cross-linking. Fourier transform infrared spectroscopy (FTIR) was performed to investigate the changes in the infrared bands related to the genipin cross-linking of the film. Microfluidization, which is a high-pressure homogenization technique, was used to homogeneously distributed CNC within the chitosan matrix and develop high strength bionanocomposite films. Response surface methodology (RSM) was adopted to systematically optimize the CNC content, the microfluidization pressure and the number of microfluidization cycles by measuring the mechanical strength of the chitosan/CNC films. Scanning electron microscopy (SEM) analysis of the microfluidized CNC/chitosan films revealed a 10 to 15 times reduction in the size of the aggregates compared to the nonmicrofluidized CNC/chitosan films. RSM was also used to develop a novel optimize formulation capable of inhibiting both gram-negative (E. coli and Salmonella spp.) and gram-positive (Listeria monocytogenes) bacteria. A nisin concentration of 125-150 μg/mL with a disodium ethylenediaminetetraacetate (Na-EDTA) concentration of 20-30 mM and a pH of 5-6 inhibited all the three bacteria. The developed antimicrobial formulation was immobilized on the surface of the microfluidized CNC/chitosan films by genipin cross-linking. Low dose gamma irradiation was applied on the films. It was found that films prepared by the combination of genipin crosslinking and gamma irradiation (1.5 kGy) the highest antimicrobial activity in vitro against E. coli and Listeria monocytogenes at the end of 35 days of storage. The films increased the microbiological shelf life of fresh pork meats by more than 5 weeks and also inhibited the growth of pathogenic bacteria in meat samples.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".