EFFECT OF WHEAT MOISTURE-CONTENT ON MEAL APPARENT PARTICLE-SIZE AND HARDNESS SCORES DETERMINED BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY

The AACC Approved Method for near-infrared reflectance (NIR) spectrosc opy to produce a wheat hardness score for wheat market classification dan be corrected for variation in wheat moisture content. The cause of the variation in NIR spectra resulting from variation in wheat moistu re was investigated. Ten samples each of soft red winter, soft white w inter, hard red winter, and hard red spring wheats were stored at 20, 40, 60, and 80 equilibrium relative humidity. Wheats were then ground on a cyclone grinder as required by the standard method. Variation in unground wheat kernel moisture content resulted in variation in NIR da ta. NIR log 1/reflectance values increased at all wavelengths as wheat moisture content increased. Spectral changes were related to changes in the apparent particle size of ground wheat meal as it was influence d by moisture content. Higher moisture contents produced slightly high er apparent particle size in meal, suggesting larger particles of peri carp that became more pliable at higher moisture (temper) levels. The apparent particle size of meal of high moisture wheats resulted in gre ater NIR radiation scattering and decreased reflectance. Meal moisture content itself had no effect on the two NTR wavelengths used to evalu ate wheat hardness.