Graduate Thesis Or Dissertation
 

Development and Validation of Sustainable Packaging Approaches for Longevity of Postharvest ‘Bartlett’ Pears and Safflower Oil

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  • The overall goal of this study was to investigate the gaps in edible packaging research in the areas of both edible coatings and edible films. This was accomplished across two distinct studies, in the pursuit of extending shelf life of fresh fruit for decreasing food loss, and heightening the consumer experience with edible packaging to decrease the environmental impact of food packaging and providing convenience to consumers. First, for reducing loss of fresh pears during postharvest storage, optimization and validation were pursued for a previously developed ‘Bartlett’ pear edible coating comprised of a cellulose nanocrystal Pickering emulsion within a chitosan matrix. Stability of coatings and derived films were assessed under ambient conditions (23±2 °C and 50±5% RH) for 10 days by correlating with oleic acid (OA) concentration between 1, 2, and 3%. The 1% (1OA) and 2% (2OA) incorporated coatings showed better stability than the 3% (3OA) incorporated option, and were thus applied to pears in a large-scale industrial cold storage trial (-1.1 °C) across 7 months, in comparison with controlled atmosphere storage (CAS), carnauba wax coating, and an uncoated control. Appearance quantification showed the highest chlorophyll retention in 2OA coated pears throughout storage (p < 0.05), only losing 58% of chlorophyll when ripened after 5 months, compared to 69% from 1OA and 89% in the control. The 2OA and 1OA coatings also significantly (p < 0.05) decreased the ethylene production peak compared to all other treatments, at 31.91 μL/Lgh and 35.72 μL/Lgh, respectively, and 2OA coating delayed the spike by 2 months compared to the control. Promising results were also quantified in significant (p < 0.05) retention of titratable acidity values from 2OA and 1OA coated pears after 7 months of storage. Improved appearance, storage life, and metabolic stability results from this study were promising for industrial ‘Bartlett’ pear Pickering emulsion coating application and shelf life extension, providing insight for coating development for other pear varieties or altogether different agricultural commodities. The second study developed and analyzed edible, water-soluble, heat-sealable, antioxidant films, their applicability as single serving pouches of edible oil (safflower oil), and their improvement with incorporation of cellulose nanocrystals. A 23 full factorial design was executed with two polymers (hydroxypropyl methylcellulose (HPMC, 1.0% w/w) and soy protein isolate (SPI, 5.0% w/w)), two concentrations of antioxidant (DL-α-tocopherol acetate, 0.1 or 0.2% w/w), and two levels of hydrophobicity (oleic acid, 0.0% or 0.25% w/w). Cellulose nanocrystals were incorporated as a filler into the HPMC or SPI matrix at 2, 4, and 6% (w/w dry weight of polymer). It was found that all HPMC-based films were fully water soluble at temperatures < 55 °C and significantly decreased in heat sealability with incorporation of oleic acid (p < 0.05). The HPMC-based oil pouches did not show antioxidant functionality on safflower oil after 60 days in accelerated storage conditions (35±2 °C and 30±2% RH). Incorporation of oleic acid increased heat seal strength of SPI films from 99 N/m to 143 N/m with, and all SPI films disintegrated in water from 20-90 °C. The SPI-based oil pouches had excellent antioxidant functionality, superior to HPMC pouches and a polypropylene control. Incorporation of cellulose nanocrystals at 2% significantly (p < 0.05) improved the water vapor permeability and tensile strength of HPMC films, but no enhancement was quantified on SPI films. Interestingly, all HPMC films with or without CNC had significantly (p < 0.05) lower oxygen permeability than that of all SPI films in ambient conditions (23±2 °C and 50±5% RH). This study demonstrated the versatility of properties and applications of edible films, and the potential for replacing current plastic packaging while leaving room for further optimization.
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  • Partially funded by the Oregon Department of Agriculture Specialty Crop Block Grant
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  • Pending Publication
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  • 2020-11-13 to 2021-06-14
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