Stability of 2170nm as a Key Wavelength for Protein Analysis by Near Infrared Spectroscopy

Abstract

Effects of food constituents, temperature and pH on near infrared spectroscopy for protein in aqueous solution in a transmittance mode were investigated. Bovine serum albumin was used as a model protein. Clear absorptions of the second derivative spectrum, which were due to protein, were observed at 1692, 1738, 1856, 2056, 2170 and 2286nm. Of these absorptions, the absorption at 2170nm was not significantly influenced in terms ofwavelength and absorption intensity even when salt, sugar, amino acid, oil and detergent were present, and even when pH and temperature were changed. These results suggest that a choice of the wavelength 2170nm is required to determine protein content with a high accuracy.