John R. Pedersen

Effect of threshing different sorghum cultivars on Sitotroga cerealella (Oliv.) and Sitophilus oryzae (L.) (Lepidoptera: Gelechiidae and Coleoptera: Curculionidae).

Abstract Laboratory studies were conducted to determine the effect of threshing different sorghum cultivars on Sitotroga cerealella (Oliv.) and Sitophilus oryzae (L.). In a no-choice test, data on progeny production, loss in grain weight, duration of development, and cultivar index of susceptibility indicated that both species of insect responded differently when bred on unthreshed and threshed sorghum grain. On the average, unthreshed sorghum was more suitable than threshed sorghum for the development of S. cerealella, whereas threshed sorghum was found to be more suitable than unthreshed sorghum for S. oryzae development. Threshing did not have any influence on loss in grain weight due to the feeding activities of the larva of S. cerealella, but S. oryzae caused considerably greater loss to threshed than unthreshed sorghum grain. The duration of development of both species of insect was not affected by threshing, but cultivar index of susceptibility was. The different sorghum cultivars had a significant effect on the performance of both S. cerealella and S. oryzae, indicating that some factors in the cultivars and in the insects themselves were responsible for the observed variation. In a free-choice test, where unthreshed and threshed sorghum grain was exposed to S. oryzae in the same chamber, more progeny were produced in the threshed than unthreshed sorghum.

Analysis for Extraneous Matter

Analysis for extraneous matter is an important element both in the selection of raw materials for food manufacturing and for monitoring the quality of processed foods. Defect action levels (DALs) of specific products are established for amounts of extraneous matter considered unavoidable and of no health hazard. However, the presence of extraneous material in a food product is unappealing, can pose a serious health hazard to the consumer, and represents lack of good manufacturing practices and sanitary conditions in production, storage, or distribution of food. This chapter provides an overview of basic official methods to isolate extraneous matter from foods, using a series of physical and chemical means to separate the extraneous material for identification and enumeration. Major concerns in the analysis of food products for extraneous matter by traditional methods are the subjectivity of methods and the availability of adequately trained analysts. The chapter also includes an overview of more sophisticated techniques to pinpoint the nature and source of contaminants (x-ray radiography, x-ray microtomography, electrical conductance, impact-acoustic emission, microscopy techniques, near-infrared spectroscopy, and enzyme-linked immunosorbent assays).