Understanding the Thermal Stability and Environmental Sensitivity of Phycocyanin using Spectroscopic and Modelling Tools

Toong, Cally

Publication:
Understanding the Thermal Stability and Environmental Sensitivity of Phycocyanin using Spectroscopic and Modelling Tools

dc.contributor.advisor	Maria G. Corradini
dc.contributor.author	Toong, Cally
dc.contributor.department	University of Massachusetts Amherst
dc.contributor.department	Food Science
dc.date	2024-03-28T19:49:30.000
dc.date.accessioned	2024-04-26T18:25:29Z
dc.date.available	2024-04-26T18:25:29Z
dc.date.submitted	September
dc.date.submitted	2018
dc.description.abstract	Phycocyanin (PC), a pigment-protein conjugate from Arthrospira platensis, is increasingly used in foods as a natural alternative to artificial blue dyes. Although PC has been classified as a color additive exempt from certification by the Food and Drug Administration, its limited stability has hindered its widespread application in food products. The objectives of this study were: a) to evaluate the photophysical properties of PC and their sensitivity to temperature, viscosity, and water activity, b) to monitor PC’s thermal degradation based on changes in the optical properties of its intrinsic fluorophores, namely its chromophores and aromatic amino acids, and c) to extract PC’s thermal degradation kinetics parameters from non-isothermal degradation profiles and validate their predictive ability. PC’s photophysical properties were monitored in solutions with viscosities from 1 to8000 mPa s and water activities, aw, from about 0 to 1. PC’s emission intensity showed high sensitivity to aw above 0.8 and mild sensitivity to the viscosity of its local environment. The effect of temperature on PC’s photophysical properties was tested in aqueous PC solutions (0.5 mM, pH: 6.1) subjected to non-isothermal temperature profiles with target temperatures from 42.5 to 80°C. The stability of PC was monitored in terms of its photophysical properties, i.e., fluorescence emission intensity, energy, and anisotropy (r) of its chromophore at set time intervals. Additionally, the photophysical properties of PC’s aromatic amino acids (AAs) tyrosine and tryptophan (lexc: 280 and 295 nm) were recorded. The thermal degradation kinetics of PC was assumed to follow a Weibullian model, and the temperature dependence of the degradation rate parameter, b(T), a logarithmic exponential model. Changes of PC fluorescence intensity under dynamic conditions were used to extract the degradation kinetics parameters using the endpoints method. Deviations between the estimated and experimental values were less than 10% for all temperature profiles. During thermal treatments, hypsochromic shifts of AAs’ emission spectra (from 340 to 315 nm) and significant increases in fluorescence anisotropy revealed that color losses were not solely associated with an alteration of the chromophore but with conformational changes and possible aggregation of the protein subunits. An increase in viscosity of the surrounding media provided a protected effect on discoloration during heating. Adequate modeling approaches and molecular spectroscopic techniques can help to develop effective strategies to enhance thermal stability, expand its use as a color and functional ingredient and operationalize it as an endogenous sensor of food quality.
dc.description.degree	Master of Science (M.S.)
dc.identifier.doi	https://doi.org/10.7275/12556461
dc.identifier.orcid	N/A
dc.identifier.uri	https://hdl.handle.net/20.500.14394/33762
dc.relation.url	https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1733&context=masters_theses_2&unstamped=1
dc.source.status	published
dc.subject	phycocyanin
dc.subject	fluorescence
dc.subject	thermal stability
dc.subject	degradation kinetics
dc.subject	photophysical properties
dc.subject	natural color
dc.subject	Food Science
dc.title	Understanding the Thermal Stability and Environmental Sensitivity of Phycocyanin using Spectroscopic and Modelling Tools
dc.type	openaccess
dc.type	article
dc.type	thesis
digcom.contributor.author	isAuthorOfPublication\|email:ctoong@umass.edu\|institution:University of Massachusetts Amherst\|Toong, Cally
digcom.identifier	masters_theses_2/717
digcom.identifier.contextkey	12556461
digcom.identifier.submissionpath	masters_theses_2/717
dspace.entity.type	Publication