Browsing by Subject "chitosan"
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Item Auto Template Assembly of CaCO3-Chitosan Hybrid Nanoboxes and Nanoframes in Ionic Liquid Medium(2012-07-16) Chen, Hsingming AnnaRecently, there has been increased effort in researching methods for producing hollow nanostructures because of their potential impact in the fields of catalysis, separation processes, drug delivery, and energy storage and conversion devices. The purpose of this thesis is to describe a method for forming hollow inorganic-organic hybrid nanoboxes and nanoframes. This approach relies upon ionic liquid (1-butyl-3-methyl-imidazolium chloride) mediated auto-templating assembly of CaCO3 and chitosan to form nanoframes (two open faces) and nanoboxes (one open face). The average dimension of the nanostructures formed was 339 ? 95 x 299 ? 89 nm. Detailed structure of nanoboxes and nanoframes were obtained by 3-D electron tomography and X-ray diffraction. Chemical bonding was determined by FTIR, and the ratio of organics to inorganics in the nanostructures was determined by thermal gravimetric analysis. The chitosan to CaCO3 weigh ratio, mixing strength, temperature, and dialysis time were varied to further elucidate the method of formation. It was found that increasing the mixing power caused the equilibrium nanostructure dimension to decrease. On the other hand, varying the experimental temperature in the range of 80 to 160?C did not affect the nanostructure dimension. The dialysis study showed that during dialysis the nanostructure core was increasingly removed. Nanoframes were observed after 72 hours of dialysis. With further dialysis, there was continued erosion of nanoframes. Results indicate that the concentration gradient and the solubility difference between the mixture components were responsible for this transformation.Item Nanoencapsulation Strategies for Antimicrobial Controlled Release to Enhance Fresh and Fresh-Cut Produce Safety(2014-05-03) Hill, Laura EllenSpice essential oils and their constituents are powerful antimicrobials against foodborne pathogens. However, their low sensory threshold and low aqueous solubility make their application to fresh produce a challenge. Encapsulation within a biocompatible material has the potential to mask sensory attributes and increase aqueous solubility of the oils, thereby improving their applicability as antimicrobials onto fresh produce. Cinnamon bark extract (CBE), trans-cinnamaldehyde, clove bud extract, and eugenol were encapsulated in ?-cyclodextrin (BCD), poly(DL-lactide-co-glycolide) (PLGA), alginate, chitosan, and poly(N-isopropylacrylamide) (PNIPAAM) singly and in combination. All essential oil capsules were characterized for particle size and morphology, polydispersity index, entrapment efficiency, phase-solubility, and controlled release profile. Following physical and chemical characterization, the oils and their nanocapsules were analyzed for their antimicrobial activity against Salmonella enterica serovar Typhymirium LT2 and Listeria spp. using a microbroth dilution assay to determine minimum inhibitory and bactericidal concentrations at 35?C. The most efficacious antimicrobial nanocapsules during in vitro testing were BCD-CBE, PLGACBE, and chitosan-PNIPAAM-CBE, which were applied to fresh-cut romaine lettuce, along with free CBE, to determine their efficiency against L. monocytogenes in a food system. The chitosan-PNIPAAM-CBE yielded the greatest bacterial inhibition (P<0.05); therefore, it was subjected to a shelf-life study to determine if there were any effects of the particles on fresh-cut romaine lettuce quality over the course of storage. The antimicrobial nanoparticles did not significantly affect (P>0.05) overall product quality, making encapsulated essential oils a viable treatment for improving food safety without negatively impacting the product?s key attributes. This research project developed several natural antimicrobial delivery systems that each exhibited unique release properties and mechanisms, which improved the antimicrobial efficacy (P<0.05) of essential oils and their active compounds. This study sought to characterize and compare different nanoencapsulation systems based on their performance as controlled delivery systems for natural antimicrobials against foodborne pathogens, which has not been previously reported.