202 Procedure for near infrared (NIR) reflectance analysis of ground wheat and milled wheat products

Methods Type: Recommendations
Key data
Number: 202
Analyte: Protein & Moisture (Near Infrared Reflectance (NIR) analysis)
Matrix: Ground Wheat and the Products of Wheat Milling
Year of Approval: 1986
Scope: This procedure is applicable to protein and moisture determination in ground wheat and the products of wheat milling.
Principle: Analysis by NIR is dependent on calibration against a suitable standard method. Such calibration assumes an empirical model in which constituent concentration may be predicted by a linear combination of reflectance data at a number of wavelengths in an equation which includes a non-zero intercept term. Analysis of cereals by NIR is based on absorption of NIR energy at specific wavelengths, by peptide linkages between amino acids of protein molecules, by OH groups in starch molecules and by OH bonds in water molecules. Measurements at reference wavelengths and mathematical manipulation of the data are required for background correction.


  • Near infrared reflectance photometer or spectrometer: A number of firms manufacture various models of NIR instruments based upon principle 3. The individual instruments utilized must meet the performance specifications set out in 6.2., 6.3. and 6.4.
  • Grinding mill fitted with a screen of 0.5 to 1.0 mm mesh; e.g. KT 3100, KT 120, Kamas SKB 200, Udy Cyclone mill or Retsch Ultracentrifugal mill (other mills may also be suitable).
  • An electronic calculator with statistical functions or a small computer; the computing power required depends on the type of instrument and whether a new calibration is being produced or an existing one assessed.

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