Natural antimicrobial nanomaterials for food packaging applications

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dc.contributor.advisor Morris, Michael A. en
dc.contributor.advisor Kerry, Joseph en
dc.contributor.advisor Cruz Romero, Malco en
dc.contributor.author Sullivan, David Joseph
dc.date.accessioned 2020-01-09T11:42:30Z
dc.date.issued 2019
dc.date.submitted 2019
dc.identifier.citation Sullivan, D. J. 2019. Natural antimicrobial nanomaterials for food packaging applications. PhD Thesis, University College Cork. en
dc.identifier.endpage 310 en
dc.identifier.uri http://hdl.handle.net/10468/9471
dc.description.abstract Consumer demand for fresh-like, sustainable, minimally processed, and clean label food products has been increasing significantly over recent years. However, removing chemical preservative and additives from food products significantly reduces their shelf-life. To address this challenge, natural antimicrobial nanomaterials (NAMs) can be used to inhibit food spoilage microorganisms and extend the shelf-life of food products. Several of the most effective NAMs include: antimicrobial polysaccharides (chitosan (CS)), plant essential oils (oregano essential oil (OEO)), and organic acids (sorbic and benzoic acid). To this end, chitosan nanoparticles (CS NPs) were synthesised and the effects of the initial concentrations of chitosan (CS) and sodium tripolyphosphate (TPP), the CS:TPP mass ratio, the CS molecular weight (MW) and pH on the CS NP properties was assessed. Self-assembled monodisperse CS NPs with a particle size of 90 nm were successfully synthesised using solutions of low molecular weight CS at pH 4.6 and 3:1 (CS:TPP) mass ratio. However, when higher concentrations of CS were used, the application of external forces (tip sonication or Ultra-Turrax™) was necessary to induce monodispersity and reduce the particle size. While both native CS and CS NPs showed antimicrobial activity, no significant antimicrobial enhancement was observed for the NP form. Subsequently, native CS, CS NPs, and commercially-available carnosolic acid nano-solubilisates (CASB) solutions were used as part of an aerosolisation based coating method with vacuum skin packaging as additional hurdles to extend the shelf-life of highly perishable European Hake (Merluccius merluccius) fillets. Results indicated that aerosolised solutions of CS, CS NPs, and CASB on hake fillets were found to extend the shelf-life by up to 40, 50 and 55 %, respectively compared to untreated control samples. Moreover, physiochemical properties of hake fillets such as pH and colour were also found to improve with respect to storage. Regarding OEOs, the effects of different surfactants (Tween® 20 and Pluronic™ 127), the surfactant to oil ratio (2:1, 1:1, and 1:2) and physical treatments (untreated, IKA ultra-turrax or tip-sonication) on the physical properties of the nanoemulsions was evaluated. The antimicrobial activity of the monodisperse nanoemulsions was assessed and OEO nanoemulsions made from Tween® 20 in a surfactant to oil ratio of 1:1, an average droplet diameter of 131 nm and a zeta potential of 39.2 mV showed the greatest antimicrobial activity. Therefore, these nanoemulsions were applied via aerosolisation treatment on fresh European Hake (Merluccius merluccius) fillets. Aerosolisation treatment of OEO nanoemulsions on hake fillets extended the shelf-life by up to 50% compared to untreated control hake fillets. Moreover, the physiochemical properties of hake fillets such as pH and colour were also found to improve. In another approach, a simple method to attach an antimicrobial essential oil support material to a functionalised surface was investigated. SBA-15 was modified with 3-aminopropyltriethoxysilane (APTES) and was then bound to an epoxy modified surface using 3-glycidoxypropyl-trimethoxysilane (GPTS). These materials were then loaded with oregano essential oil and their physical properties and antimicrobial activity against food spoilage microorganisms assessed. Finally, the antimicrobial effects of benzoic and sorbic acid salt and their commercially-available nano-solubilisates against planktonic and biofilm cultures of Staphylococcus aureus, Pseudomonas fluorescens and chicken microflora was assessed. The organic acid nano-solubilisates were more effective compared to their organic acid salt counterpart with respect to both planktonic and biofilm cultures. However, biofilms of Staphylococcus aureus, Pseudomonas fluorescens and chicken microflora were more resistant to both organic acids salts and nano-solubilisates compared to the planktonic cultures. Overall, this thesis extends our knowledge of nanomaterials for antimicrobial control of foodstuffs and shows the potential that they may have in developing active packaging systems. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2019, David J. Sullivan. en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Nanomaterials en
dc.subject Natural antimicrobial en
dc.subject Shelf-life en
dc.subject Food packaging en
dc.subject Antimicrobial activity en
dc.subject Surface modification en
dc.title Natural antimicrobial nanomaterials for food packaging applications en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD en
dc.internal.availability Full text available en
dc.description.version Accepted Version
dc.contributor.funder Food Institutional Research Measure en
dc.description.status Not peer reviewed en
dc.internal.school Chemistry en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.check.chapterOfThesis 3, 4, 5
dc.check.embargoformat Apply the embargo to the e-thesis on CORA (If you have submitted an e-thesis and want to embargo it on CORA) en
ucc.workflow.supervisor joe.kerry@ucc.ie
dc.internal.conferring Spring 2020 en
dc.relation.project Department of Agriculture, Food and the Marine, Ireland (Project No. 11/F/038) en


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