Date of Award

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Packaging Science

Committee Chair/Advisor

William Scott Whiteside

Committee Member

George Cavender

Committee Member

Kyle Dunno

Committee Member

William Bridges

Abstract

Traditional polymers used for food packaging have raised concerns about their negative impact on the ecological system. In order to meet environmental and health requirements, this has sparked extensive study into the development of biodegradable packaging films. The use of starch-based films in place of petroleum-derived polymers is one of the viable options. Significant characteristics of starch include biodegradability, availability, and suitability for polymer blending or modification. However, because of shortcomings including poor mechanical properties and insufficient water resistance, its use in food packaging is limited, requiring more innovation to increase its profitability in this field. To overcome these challenges, in this study, pearl millet starch is reinforced with lignocellulose nanofibers (LCNFs) to improve its mechanical and water barrier properties.

LCNFs with a diameter ranging between 3-6 nm were isolated from peach pits by a combination of chemical and mechanical treatment, and the effect of lignin concentration (28, 18, 7, and 5%) on the characteristics of LCNFs was investigated. Among all LCNFs with 5% (LCNFs-16) and 7% (LCNFs-8), lignin showed the best thermal resistance and crystallinity, and therefore was used to reinforce the starch matrix.

Varying concentrations (25%, 50% and 75%) of LCNFs-16 and LCNFs-8 were incorporated into the starch (3%) matrix, and glycerol (30%) was used as a plasticizer to develop films named L-16 and L-8, respectively, via the solvent casting method. In terms of appearance, the control and LCNFs-reinforced films showed no noticeable visual difference. All the films had a thickness of around 0.1 mm, were transparent, and displayed no apparent defects like bubbles or cracks. Among all the films, L-8 films with 50% of LCNFs-8 concentration (L8-50) showed the best mechanical property, with around 628% and 1263% increase in tensile strength and Young’s modulus, respectively, compared to the control starch films. There was a 21% increase in crystallinity and a slight improvement in water barrier property (around 8%) of L8-50 film. Interestingly, LCNFs-reinforced film samples could be printed using an inkjet printer without ink spread or significant color variation.

Further, anthocyanin (BA) was extracted from blueberries using acidified ethanol. Anthocyanins have the property to change color, which is associated with their various chemical structures and varies depending on the pH level, due to their ionic nature. The buffer solution with BA ranged in color from reddish/pink to purple and then to yellow-green, during a change in pH from acidic to alkaline. Then, BA (10%, 25% and 50% of starch weight) was incorporated into starch/LCNFs film matrix (L8-50) to develop pH-sensitive film via the solvent casting. The uniform dispersion of BA through physical interactions within the matrix was confirmed by structural analysis of the starch/LCNFs/BA films using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The color shift of films in the buffer solutions from reddish-pink to greenish-yellow demonstrated that films are sensitive to pH over a wide pH range of 2 to 13. Among all the films, colorimetric analysis of starch/LCNFs/BA films with 50% BA (starch/LCNFs/BA50) showed the highest ∆E (color difference) values across the pH range of 2 to 13, and therefore, these films were considered for intelligent packaging of chicken to monitor its freshness and quality during storage at 4 °C and 23 °C. The starch/LCNFs/BA50 films exhibited potent antioxidant activity, with a DPPH radical scavenging rate of 53%. On the 10th day of storage (at 4 °C), the pH and TBARS value of chicken were recorded as 6.93 and 1.43 mg/MDA, which indicated the spoilage. Along with the spoilage of chicken, starch/LCNFs/BA50 film showed a prominent change in color from red to grayish purple. Thus, the findings of this study suggest that the developed pH-sensitive films have the potential to be used as effective indicators for monitoring freshness and also offer antioxidant protection, supporting their potential use in smart and active food packaging systems.

Author ORCID Identifier

https://orcid.org/0000-0002-8079-9670

Download

Available for download on Monday, August 31, 2026

Share

COinS