According to AOAC (Association of Official Analytical Chemists),41 extraneous material is the name given to "any foreign matter in product associated with objectionable conditions or practices in production, storage, or distribution." If the extraneous matter is contributed by insects, rodents, birds, or other animal contamination, it is referred to as filth. The major components of extraneous matter in food products are insect fragments, rodent hair, and feather fragments. A standardized analytical method exists for counting insect fragments (AOAC41,42). Although the sample preparation and counting techniques are very well standardized, a lot is to be desired for the identification process. The author has sent the same preparations to three different laboratories and found results varying by two orders of magnitude. Most of the literature on identification of insect fragments is based on agricultural or storage insects and not on aquatic insects that are normally present in outdoor ponds. In addition, it is often difficult to distinguish between insect parts and plant parts, resulting in an over-estimation of "unidentified insect" parts. Researchers at Earthrise Nutritionals and the University of Texas at Austin have developed a method to quantify insect fragment biomass in microalgal products using a myosin enzyme-linked immunosorbant assay (ELISA) technique.43 This new method provides an improvement on the standard method that registers insect fragment counts irrespective of the large differences in insect fragment size that are commonly observed.
The presence of rodent hair in microalgal products is considered to be an indicator of potential contamination. It is very rare to observe rodent hair when proper pest control measures are taken (Table 1.3). Feathers, plant fragments, and any other extraneous material are normally strained during pond netting and preharvest screening.
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