Near Infrared Spectroscopic Studies of Changes in Stored Grain

Abstract

The potential for near infrared (NIR) spectroscopy to be used to detect quality changes in stored grain was investigated. Wheat, barley and canola were stored at different temperatures and moisture content for a period of 12 months. NIR reflectance spectra of the samples recorded prior to storage were contrasted against the spectra of the samples stored under various conditions by calculating the root mean squares of the point-for-point spectral differences. The ability of NIR to indicate whether there were changes occurring in the grain was determined by the spectral differences being greater than the differences due to repacking. Changes in NIR spectra were low in grain stored at low temperatures and moisture content, but increased in grain stored under more adverse conditions. For wheat and barley stored for 12 months at 30°C and 14% moisture content, spectral contrasts increased to 1294 and 790 microabsorbance units, respectively. Changes in spectral contrast of canola were higher with contrasts of canola stored for 12 months at 30°C and 8% moisture content reaching 2700 microabsorbance units. In order to confirm that the changes seen in the contrast were due to changes in the grain and not due to the drift in the NIR instrument, a stable chemical standard (polyethylene) was used as a control. The results show that spectral differences can be used to monitor the post-harvest maturity of wheat and barley. Spectral changes observed in standard cells containing wheat and barley decreased after six months. The continual high rate of change observed in spectral differences of canola makes it unsuitable for use in standard cells.