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theses

Edible films and coatings have been regaining interest due to consumer trends in natural, clean-label, and biodegradable materials in the past decades with increasing awareness for the environment. The concept of active or intelligent package utilizing the biodegradable materials has been introduced to the food industry, as a new strategy to enhance and monitor shelf-life and food quality. In addition, the growing trend of functional food is driving the search for a method to exploit nutraceuticals, as they can not only provide health benefits, but also improve food safety and shelf-life. Many of the recognized nutraceuticals are plant-source polyphenols, most of which are hydrophobic. Despite a large number of their benefits, the application of such nutraceuticals in food is limited by their physicochemical and physiological properties, such as poor solubility, chemical degradation in food matrices, and low bioavailability. In order to solve this problem, there have been numerous attempts to utilize various colloidal systems instead of chemical modification, which is not desirable considering the current trend. Nanotechnology has been employed in formulating such colloidal systems, and the majority use excipients, such as lipids, or biopolymers as a carrier to encapsulate nutraceuticals. However, the use of excipients is not always beneficial as they may add extra calories to the food, or complicate the system because they tend to be sensitive to environmental change. Thus, there is an unmet need to investigate a straight-forward size-reduction method to obtain nano-scale nutraceuticals. Furthermore, even with the numerous supporting evidence, the size dependence on the nutraceuticals’ function, as well as the mechanism of the size reduction effect, remains to be explored in detail. Additionally, although the potential application of nutraceutical incorporated edible films have been demonstrated in the past, the physical and chemical structural understanding of the system needs to be elucidated further in order to utilize them more effectively.

To address this issue, this study demonstrates the relationship between physical properties and chemical/biological functionalities with nanoparticles and nanoemulsions of nutraceuticals fabricated by acousto-plastic deformation. The particle size as well as surface properties are determined to have a significant effect on the improvement of antioxidant and antimicrobial effects of solid and liquid nutraceutical models including curcumin, essential oils and α-tocopherol. The improved antioxidant effect by size reduction is demonstrated to be attributed to the physical property changes including amorphous fraction increase in the crystalline structure of solid particles and enhanced solubility resulted from it. The improved antimicrobial effect is shown to be mediated by electrostatic attraction between nutraceuticals and bacterial cells, resulting from the surface charge of nutraceutical nanoparticles. Finally, utilizing the nano-formulation developed in this study, predictive quantification of bacterial growth parameters is obtainable in order to use an antimicrobial agent more effectively.

Subsequently, a fabrication method of nano-scale nutraceutical-laden edible films is established in this study. Using the system, the physical/structural interaction of nutraceutical nanoparticles/nanoemulsions with film polymeric matrices are determined to be a critical factor for either of the components in that it can change the final films’ properties and also it can improve the functional action – i.e., antioxidant and antimicrobial effect - of incorporated nutraceuticals. Using the combination of two strategies - nanotechnology and edible films - the antioxidant effect of curcumin is shown to exhibit a 28-fold increase compared to commercial unprocessed curcumin particles. Furthermore, curcumin nanoparticle laden HPMC edible films are demonstrated to have a potential to be used as a biosensor to monitor seafood spoilage in food packaging, by responding to a pH change resulting from the volatile amines by microbial degradation. The edible films with nutraceuticals developed in this study show a potential to enhance and monitor the shelf-life and quality of food products. Our demonstration of interactions within a particulate/emulsion system as well as between colloid-polymeric systems provides information to improve the efficacies of nutraceuticals which contributes to the food industry.

ETD_10372

Ph.D.

Includes bibliographical references

doi:10.7282/t3-1kc6-bh77

ETD doctoral

The author owns the copyright to this work.