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ORCID

https://orcid.org/ 0000-0001-9347-7243

Access Type

Open Access Thesis

Document Type

thesis

Degree Program

Food Science

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2022

Month Degree Awarded

February

Abstract

There has been a notable rise in the alternative protein market in the recent years which promotes an interest in the research of both animal and plant proteins to establish better structure-function relationships. Over the years many analytical tools have been used to study proteins and compare them, however Raman Spectroscopy and Surface Enhanced Raman Spectroscopy (SERS) have not been as much used for this application. SERS consolidates Raman Spectroscopy that primarily measures molecular vibrations and nanostructures that enhance the weak Raman signals. The objective of this study is to explore the capability of the Raman instrumentation in combination with different substrates for spectroscopic analysis of 3 animal proteins viz. whey, k-casein and albumin from chicken egg white and 4 plant proteins namely mung bean, soy, pea and faba bean. Herein, we firstly established a method that could be applied to all proteins to detect characteristic peaks that are related to their structure. Of all the methods, SERS with silver dendrites was the most promising method that detected protein characteristic peaks, particularly the shifts around 700-900 cm-1 attributed to the CN stretch and tryptophan groups. Although different proteins exhibit similar spectral characteristics, they were discriminated using principal component analysis. Then we explored the optimal method to study the effect of different environmental conditions including pH and salt concentration on the protein spectroscopic analysis. The limitations of the substrates were better understood during this process as Ag dendrites failed to provide a spectrum in the high pH range but was compatible with different salt concentrations. The peaks in the Amide-I region were vi used as a marker to study the effect of change in pH and salt. Most proteins showing a shift in the band suggesting a transition from α-sheet to a random coil conformation. The acquired spectra and subsequent PCA results depicted that pea protein was the most susceptible to change in pH amongst other proteins whereas faba bean was susceptible to a change in salt concentration. Finally, these learnings were applied to analyze a real-world food product to compare its spectroscopic characteristic with the standards we have. In conclusion, we demonstrated that Raman Spectroscopy and SERS was able to provide distinct spectroscopic characteristics of plant and animal proteins that may be used to facilitate the quality control or product development of novel plant-based food products. Future work will investigate the relationship between the spectroscopic characteristics and the structural function of proteins.

DOI

https://doi.org/10.7275/26881422

First Advisor

Lili He

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