Rapid assessment of insect fragments in flour milled from wheat infested with known densities of immature and adult Sitophilus oryzae (Coleoptera: Curculionidae).

Milling wheat, Triticum aestivum L., infested with low densities of internal feeding insects can result in flour containing insect fragments. The Food and Drug Administration (FDA) enforces a standard or defect action level stating that a maximum of 75 insect fragments per 50 g of flour is allowed. However, the relationship between level of infestation and number of resulting fragments is not well documented, and a more rapid method for enumerating insect fragments is needed. We characterized the number of insect fragments produced from milling small lots of wheat spiked with known densities and life stages of Sitophilus oryzae (L.) (Coleoptera: Curculionidae). Insect fragments were enumerated with near-infrared spectroscopy (NIRS), a quick nondestructive procedure, and with the industry standard flotation method. Results showed that an individual small larva, large larva, pupa, or adult produced 0.4, 0.7, 1.5, and 27.0 fragments, respectively. NIRS-predicted counts of < or =51 (from small larvae), < or =53 (from large larvae), < or =43 (from pupae), or 0 (from adults) indicated that there were <75 actual fragments in that sample, because the upper bound of associated 95% inverse prediction confidence intervals was less than the standard; NIRS-predicted counts of > or =98, > or =117, 108, or > or =225 fragments (same life stages as above) signaled that these flour samples contained >75 actual fragments. These data suggest that NIRS could be adopted for rapid assessment of insect fragments resulting from relatively low levels of infestation with immature life states, but that it was not accurate enough for enumerating insect fragments, relevant to FDA standards, resulting from adults.