Study of acetylated food proteins by Raman spectroscopy

Abstract

Three food proteins, soy protein isolates, spray-dried egg white, and whey protein isolates, were acetylated to varying levels, and the extent of modification was determined by wet chemistry methods. Raman spectra of the modified proteins were obtained. A new C=O stretching vibration was observed at 1737 cm -1 and was attributed to ester carbonyl groups appended to the proteins during acetylation. Calibration curves were obtained by plotting the intensity ratio of this Raman band to the 1003 cm -1 phenylalanine stretching band against the extent of substituted hydroxyl groups. Linear fits were obtained with correlation coefficient r > 0.9979. The Raman spectral data were also analyzed to study the effect of acetylation on the conformation of the 3 proteins. Marked conformational changes were observed in the modified proteins.