egg (Central Science Laboratory, 2004a), and milk test kits (Central Science Laboratory, 2004a).
Highly variable food matrices and the nature of food production also create sampling challenges. The distribution of allergenic proteins within whole foods is not necessarily homogenous, and allergenic ingredients may not be evenly distributed throughout processed foods. In addition, cross-contact may result in a heterogeneous distribution of allergens within or on a food. For example, nuts may be introduced into chocolate on a production line where nut-containing and nut-free products are processed sequentially. In this case, cross-contact is most likely to occur at the beginning of a production run for the nut-free product. Thus, allergen testing using chocolate taken from the end of a production run might not adequately characterize the risk.
For a food product, development of a scientifically sound sampling plan that includes a statistical analysis of the probability that any allergens present are detected and measured accurately. Important sampling questions that need to be considered include whether the allergen is likely to be heterogeneously distributed within the batch; the number of samples per batch that should be tested; which batches should be tested; which portion of a run should be tested; and how to obtain a specific degree of confidence (e.g., 95% confidence) that no allergen is present.
H. Collective Allergens Three of the major food allergens identified in the FALCPA are actually groups of foods: crustaceans, fish, and tree nuts. It is possible that proteins from two or more species within each of these “collective allergens” might be present in a food and the available analytical methods are unable to distinguish between species in a group. Therefore, it may be necessary to consider total protein levels from all species in a group rather than the level of protein from each species. In addition, an individual allergic to one species is likely to also be allergic to other species in the group.
The ability of available test methods to distinguish different species within each group of “collective allergens” varies. To date, there are no commercially available test kits for finfish proteins and only one for crustacean tropomyosin. Ben Rejeb et al. (2003) reported the development of an ELISA for shrimp that showed significant cross-reactivity with other crustaceans. There are three commercially available tree nut test kits (two for hazel nut, one for almond), but the species specificity of these kits is not clear. Hlywka et al. (2000) showed that an almond ELISA detected protein from seven other tree nuts. The hazel nut ELISA developed by Holzhauser et al. (2002) showed cross-reactivity with other nuts, and the walnut assay developed by Niemann and Hefle (2003) reacted with three other nut species. Wei et al. (2003) developed an ELISA for cashew that showed cross-reactivity with several other nuts. Ben Rejeb et al. (2003) developed a hazel nut- specific ELISA that did not cross-react with other nuts, and Clemente et al. (2004) developed a Brazil nut assay with “negligible” cross reactivity to five other nut species.
Although not likely to be useful for routine screening or testing, techniques such as liquid chromatography/mass spectrometry (LC/MS) are being used to identify specific
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