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Development of Modified Nanostructures for Fabrication of Polymer Nanocomposite Films for Controlled Atmosphere Food Packaging

Riahi, Zohreh | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54990 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Bagheri, Reza; Pircherghi, Gholamreza; Mohammadpour, Raheleh
  7. Abstract:
  8. Active packaging is a novel approach that can ensure food safety by removing undesirable compounds such as Oxygen, ethylene, moisture, and microbial contamination from fresh produce's environment and reducing product loss by extending shelf life. Current research on active food packaging materials focuses on using biopolymers such as carbohydrates, proteins, and lipids as alternatives to non-degradable petroleum-based packaging materials. Active nanomaterials are commonly used to impart functionality to packaging materials. However, the lack of functionality limits their industrial application.Therefore, the main objective of this work was to fabricate bioactive nanocomposite films by incorporating TiO2-nanostructures, Carbon quantum dots (QDs), and sulfur quantum dots (SQDs) as functional materials for increasing shelf life of the food product. In the first study, titanium nanotubes (TNTs) were synthesized, and their photocatalytic antimicrobial and ethylene scavenging activity were investigated after surface modification with Cu(II) and Cu(I) oxides (TNT-CuO, TNT-Cu2O). The TNT−Cu2O showed reasonable functional properties, indicating a substantial 65% ethylene removal and a distinctive bactericidal effect after 300 and 180 min. Then, the TiO2 nanostructures-added cellulose nanofiber (CNF) films with good optical and mechanical properties were prepared. CNF-based films were incorporated in packaging of tomatoes. Strong antibacterial and ethylene scavenging activities of the mentioned films increased the tomatoes' shelf life by 14 days. In the second study, Sulfur quantum dots (SQD) were fabricated using hydrothermal method. Unlike other sulfur-based fillers, the SQD showed 100 % antioxidant and strong antimicrobial activity. The alginate-based films incorporated with 3% SQD showed 82 % UV barrier, high transparency, and improved mechanical and water barrier properties. The Alginate/SQD exhibited antioxidant and antimicrobial properties, inhibiting mold growth and extending bread shelf-life by 14 days. In the third study, chitosan-based carbon quantum dots (CQDs) were synthesized and showed high antioxidant and antimicrobial activity at short time and low concentrations. Carboxymethyl cellulose (CMC)-based functional films were fabricated by adding 1, 3, and 5wt% of CQD. The addition of 3wt% CQD formed a highly transparent film with 100 % UV-blocking properties and increased the base polymer's tensile strength and wettability (up to ~30 %).Edible coating of lemon fruits with the CMC/CQD film showed an excellent effect in preventing mold growth and extending the shelf life of the fruit by 21 days, confirming the antioxidant and antibacterial effect of the CQD-added film. The results show that the prepared films with excellent physical and functional properties are expected to be promising for active food packaging applications to extend the shelf life of fresh fruits, according to the product spoilage mechanism
  9. Keywords:
  10. Polymer Nanocomposits ; Active Packaging ; Titanium Dioxide ; Alginate ; Cellulose Nanofiber ; Carbon and Sulfur Quantum Dots

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