Determination of low levels of mite and insect contaminants in food and feedstuffs by a modified flotation method

Extraneous material was separated from feed and food products by a modified technique in which kerosene is used in a specially designed flotation flas k. This technique, although effective for analyzing feed and foods, present ed limitations in the analysis of finely powdered materials. Some procedura l modifications and an increased in the capacity of the flotation flask fro m 500 to 750 mt allowed a larger sample weight (20 g) to be analyzed for mi tes, insect fragments, and rodent hairs, with considerably reduced residue interference. In trials with a variety of products seeded with known number s of mites, average recovery was 83%. Recoveries of 89% were obtained from flour samples seeded with insect fragments and rodent hairs, A new process of suspending extracted mites in a mixture of industrial methylated spirit (46%) and glycerol (54%) by volume was used to allow rapid and more precise estimates of mite populations in heavily infested samples.