159 Determination of Protein by Near Infrared Reflectance (NIR) Spectroscopy

Methods Type: Generic Methods
Key data
Number: 159
Analyte: Protein (NIR Spectroscopy)
Matrix: Ground Wheat and Flour
Year of Approval: 1995
Scope: This method is applicable to ground wheat and flour.
Principle: NIR reflectance spectroscopy is a rapid instrumental technique for the analysis of cereals both in the laboratory and on-line. It is based on absorption of NIR energy at specific wavelengths by peptide linkages between amino acids of protein molecules and at reference wavelenghts. Mathematical processing of the spectral data and calibration against a suitable reference method enables the protein content to be determined. Inclusion of a measurement at a wavelength corresponding to an absorption by water enables the result to be corrected automatically to a dry weight basis or on a standard moisture basis.


  1. Near infrared fixed filter instrument or monochromator capable of measurement at 2230, 2180, 2100, 1940 and 1680 nm.
  2. Grinding mill. Screen sizes of 0.5, 0.8 or 1.0 mm mesh are acceptable.
  3. A personal computer with multiple regression software (if not incorporated in 1.).


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