DETECTION OF EXTERNAL AND INTERNAL INSECT INFESTATION IN WHEAT BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY

Near-infrared spectroscopy (NIR) in the reflectance mode was investiga ted for the rapid, automatic and non-destructive detection of insect s tored-grain pests external or internal to wheat kernels. Convincing ca libration performance was obtained for external adult Oryzaephilus sur inamensis (L) (saw-toothed grain beetle) in unmilled samples including varieties Beaver (soft wheat) and Mercia (hard wheat) at two moisture contents. With this large substrate variability, the method could dif ferentiate between uninfested samples and samples with approximately 2 70 insects kg(-1) or more. Milling made no improvement. Large spectral differences were observed between uninfested kernels and kernels infe sted internally with Sitophilus granarius (L) (grain weevil) larvae or pupae, arising from both a changed chemical composition and physical structure. Single uninfested and infested kernels were discriminated b y their second derivative (d(2)) spectra. For both external and intern al infestation there was substantial evidence that insect protein and/ or chitin and moisture were being detected. NIR should be useful as a rapid method of detection.