This work is focused on the design, production and characterization of sustainable active food packaging materials with antimicrobial and antioxidant properties to ensure the safety and quality of foods and prolong their shelf-life. Firstly, a microfluidic device combining dielectrophoresis (DEP) and Raman spectroscopy was developed for a fast and dynamic characterization of different bacterial strains, including food-related pathogens (i.e. E. coli and S. aureus), directly in planktonic suspension. Predictive models to identify bacterial cross-induced resistance to antibiotic within few hours were built using this method, overcoming the overnight incubation required by classical microbiological assays. Furthermore, Raman imaging was employed to detect the spatial distribution of different biomolecules at single cell level. Then, the antibacterial properties of innovative silver and carbon-based nanosystems and their inclusion in prototype packaging materials were studied. Differently sized silver nanoparticles, from 6 to 50 nm, were compared for their antibacterial efficacy in suspension and immobilized on glass. For the first time, the surface minimal bactericidal concentration (SMBC) of silver needed to kill 99.9999% of bacteria, was determined by ISO 22196, thereby facilitating the comparison between measurements and minimizing the amount of silver on the materials surface (0.023-0.034 μg/cm2) as well as their cost of production and toxicity. Colloidal carbon nanoparticles (CNP), obtained by a green chemistry synthesis, were tested against Gram + and a Gram – bacteria, by classical microbiological assays and the DEP-Raman system, revealing a rapid interaction with the bacteria but not significant bactericidal effects. Thus, CNP were loaded with an antimicrobial peptide which increased their antibacterial activity, especially against S. aureus. Finally, new antioxidant packaging modified with grape and olive industrial waste products and Moringa oleifera leaves obtained by different extractive procedures were produced and characterized. The antioxidant efficacy of many fractions of the plants extracts were analyzed by multiple standard assays and the results were correlated with their content of polyphenols obtaining higher values for anti-solvent and maceration extract fractions. The latter, resulting from a more sustainable extraction procedure, were included in cellulose-based active packaging systems. The antioxidant properties of such films were measured by indirect and direct analytical methods demonstrating good free radical scavenging properties for all the three kind of active agents and a higher radical reduction capacity of moringa. Additionally, the ability of the packaging coated with moringa (5% w/w) of delaying fresh ground beef oxidation was tested. This film was chosen as the best alternative to obtain the highest oxidative protection of meat on the basis of the in vitro results and ensuring a direct food-contact mechanism of action. This packaging revealed to prevent meat from lipid oxidation by at least 60% after 16 days compared to simple cellulose. Additionally, in situ analysis of the meat performed by vibrational spectroscopies evidenced also a protective action against protein and lipid degradation. This work could be considered valuable in the field of food packaging because the use of sustainable and degradable materials to prolong the food shelf-life perfectly fits in the actual compelling need to reduce pollution and global waste production. This is in accordance with the 12th Sustainable Development Goal of the European Green Deal purpose to halve the global food waste production per capita by 2030, ensuring an efficient and sustainable use of natural resources. Hence, an innovative way to recover food industry waste is proposed and their antioxidant efficacy in active food packaging was demonstrated even on real food matrices with many different techniques strengthening the reliability of the results.
Study of antimicrobial and antioxidant properties of new materials for development of active food packaging / Barzan, Giulia. - (2022 Jun 20).
Study of antimicrobial and antioxidant properties of new materials for development of active food packaging
BARZAN, GIULIA
2022
Abstract
This work is focused on the design, production and characterization of sustainable active food packaging materials with antimicrobial and antioxidant properties to ensure the safety and quality of foods and prolong their shelf-life. Firstly, a microfluidic device combining dielectrophoresis (DEP) and Raman spectroscopy was developed for a fast and dynamic characterization of different bacterial strains, including food-related pathogens (i.e. E. coli and S. aureus), directly in planktonic suspension. Predictive models to identify bacterial cross-induced resistance to antibiotic within few hours were built using this method, overcoming the overnight incubation required by classical microbiological assays. Furthermore, Raman imaging was employed to detect the spatial distribution of different biomolecules at single cell level. Then, the antibacterial properties of innovative silver and carbon-based nanosystems and their inclusion in prototype packaging materials were studied. Differently sized silver nanoparticles, from 6 to 50 nm, were compared for their antibacterial efficacy in suspension and immobilized on glass. For the first time, the surface minimal bactericidal concentration (SMBC) of silver needed to kill 99.9999% of bacteria, was determined by ISO 22196, thereby facilitating the comparison between measurements and minimizing the amount of silver on the materials surface (0.023-0.034 μg/cm2) as well as their cost of production and toxicity. Colloidal carbon nanoparticles (CNP), obtained by a green chemistry synthesis, were tested against Gram + and a Gram – bacteria, by classical microbiological assays and the DEP-Raman system, revealing a rapid interaction with the bacteria but not significant bactericidal effects. Thus, CNP were loaded with an antimicrobial peptide which increased their antibacterial activity, especially against S. aureus. Finally, new antioxidant packaging modified with grape and olive industrial waste products and Moringa oleifera leaves obtained by different extractive procedures were produced and characterized. The antioxidant efficacy of many fractions of the plants extracts were analyzed by multiple standard assays and the results were correlated with their content of polyphenols obtaining higher values for anti-solvent and maceration extract fractions. The latter, resulting from a more sustainable extraction procedure, were included in cellulose-based active packaging systems. The antioxidant properties of such films were measured by indirect and direct analytical methods demonstrating good free radical scavenging properties for all the three kind of active agents and a higher radical reduction capacity of moringa. Additionally, the ability of the packaging coated with moringa (5% w/w) of delaying fresh ground beef oxidation was tested. This film was chosen as the best alternative to obtain the highest oxidative protection of meat on the basis of the in vitro results and ensuring a direct food-contact mechanism of action. This packaging revealed to prevent meat from lipid oxidation by at least 60% after 16 days compared to simple cellulose. Additionally, in situ analysis of the meat performed by vibrational spectroscopies evidenced also a protective action against protein and lipid degradation. This work could be considered valuable in the field of food packaging because the use of sustainable and degradable materials to prolong the food shelf-life perfectly fits in the actual compelling need to reduce pollution and global waste production. This is in accordance with the 12th Sustainable Development Goal of the European Green Deal purpose to halve the global food waste production per capita by 2030, ensuring an efficient and sustainable use of natural resources. Hence, an innovative way to recover food industry waste is proposed and their antioxidant efficacy in active food packaging was demonstrated even on real food matrices with many different techniques strengthening the reliability of the results.File | Dimensione | Formato | |
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https://hdl.handle.net/11583/2970684