Raman spectroscopic study of deamidated food proteins

Authors

Hing Wan Wong, The University of Hong Kong
Siu Mei, Emily Choi, Technological and Higher Education Institute of Hong Kong, Vocational Training CouncilFollow
David Lee Phillips, The University of Hong Kong
Ching Yung Ma, The University of Hong Kong

Staff Page Link

Dr CHOI Siu Mei, Emily

Document Type

Journal Article

Publication Date

2009

Keywords

Deamidation, Raman spectroscopy, Soy proteins isolates, Spray-dried egg white, Whey protein isolates

DOI

10.1016/j.foodchem.2008.09.027

Abstract

Three food protein products, soy and whey protein isolates and spray-dried egg white powder, were deamidated to various levels by 0.04 N hydrochloric acid. The extents of deamidation were determined using an ammonia electrode. Raman spectra of the modified proteins were obtained and analyzed. A new C{double bond, long}O stretching vibration band was observed at 1780 cm -1, attributed to γ-carboxyl groups of aspartic and glutamic acids. Calibration curves were constructed by plotting the intensity ratio of the 1780 cm -1 band to the 1003 cm -1 phenylalanine stretching band (as an internal standard) against the extent of deamidation. Linear fits were obtained with high correlation coefficients r > 0.987. Effect of deamidation on the conformation of these proteins was also studied by monitoring changes in Raman spectral characteristics, including a transition from ordered to disordered structures, exposure of tryptophan residues from a buried, hydrophobic microenvironment, and probable conformational changes of the aliphatic residues.

Source Publication

Food Chemistry

Volume Number

113

Issue Number

2

First Page

363

Last Page

370

Recommended Citation

Wong, H.,Choi, S.,Phillips, D.,& Ma, C. (2009). Raman spectroscopic study of deamidated food proteins. Food Chemistry, 113 (2), 363-370. http://dx.doi.org/10.1016/j.foodchem.2008.09.027