Date of Award

Spring 5-6-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Food and Nutrition Sciences

Advisor

Denise I. Skonberg

Second Committee Member

Caitlin Howell

Third Committee Member

Mehdi Tajvidi

Additional Committee Members

Douglas W. Bousfield

William Gramlich

Abstract

A majority of the polymers obtained from fossil fuels are synthetic and microorganisms do not possess the enzymatic machinery to degrade them. Therefore, these materials persist and harm our environment and our ecosystems. An alternative approach to the use of synthetic polymers would be to use biodegradable materials, materials that are already found in nature. One such material, cellulose nanofibrils (CNFs), are nano scale fibers obtained from mechanical disintegration of paper pulp. Due to their physico-chemical properties, they can form strong interconnected films with good barrier properties, with the potential to replace fossil fuel based synthetic food packaging. However, being a polysaccharide, a deterioration in film properties is observed upon contact with moisture, thereby, preventing its adoption by the food industry. In this research, phenolic acids, amino acids, fatty acids and corn protein were utilized to modify premade CNF films, to improve their water repellency, whilst introducing active functionalities such as antioxidant and anti-bacterial adhesion activity. The modified films were assessed for their hydrophobicity, mechanical property, antioxidant activity, bacterial adhesion, evidence of modification and their capacity to enhance the shelf life of food products. Results indicated that the type of organic acid and the reaction methodology used had a significant impact on the hydrophobicity, mechanical property, bacterial adhesion, and antioxidant activity of the films. Esterification to an organic acid with a lower hydrophobic-lipophilic balance (HLB) enhanced the hydrophobicity of the CNFs. Antioxidant activity in general improved for CNFs when esterified/crosslinked with phenolic and amino acids. Depending on the organic acid used and the specific food matrix evaluated, varying shelf life enhancing effects were observed for modified CNF films. Modification resulted in a slight reduction in mechanical properties, but a significant improvement in wet strength was observed. Therefore, from this research it can be understood that the esterification/crosslinking of premade CNF films using different organic acids and proteins can improve the water repellency of CNFs. Similarly, additional functionality such as antioxidant and antimicrobial properties can be introduced, paving the way for additional research as well as potential adoption by the food industry as a food packaging system.

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