Doctor of Philosophy, The Ohio State University, 2022, Food Science and Technology

As natural colorants get more attention in the food industry, efforts on anthocyanin (ACN) stabilization and color expression have increased for their incorporation in food products. Studies show enhancement of ACN color performance and resistance to degradation by stabilizing the pigment via intramolecular copigmentation. This reaction occurs between the ACN chromophore and its covalently bound acyl group on the glycoside. In plants, most acylating groups exist in the trans-isomeric configuration but can undergo excitation under ultraviolet and visible light to induce the cis-conformation. The applied radiant energy affects the isomerization barrier, causing the molecule to adopt its excited state, and producing a molecule with different chemical characteristics. Photochromism, defined as “light-induced, reversible change in color,” is the reaction that occurs when photoisomerization of molecules lead to a change in color. Relatedly, cis- and trans- acylated ACN have been known to exhibit differences in color expression and stability, but details on the factors affecting photochromism has not been well studied. The overall objective of this study was to investigate the conditions that influence photochromism of acylated ACN and compare the cis-trans isomers' spectroscopic characteristics, colorimetry, and stability in various pHs. In the first objective, the effects of irradiation time and excitation energy on ACN cis-trans isomerization and color expression were studied. East Asian eggplants were chosen as the source of the pigment, due to their simple ACN profile that contained the trans-isomer necessary to induce isomerization. Delphidin-3-(trans-p-coumaroyl)-rutinoside-5- glucoside, delphinidin-3-(cis-p-coumaroyl)-rutinoside-5-glucosde, and a semi-crude extract containing both isomers were characterized, standardized, and subjected to excitation (UV chamber at 254 nm, 365 nm, visible light with D65 lamp, and F2 lamp) for up to 20 hours. All four radiant ener (open full item for complete abstract)

Committee: M. Monica Giusti (Advisor); Rafael Jimenez-Flores (Committee Member); Luis Rodriguez-Saona (Committee Member); Emmanuel Hatzakis (Committee Member) Subjects: Agricultural Chemicals; Analytical Chemistry; Food Science