T. J. Fu1 , N. Maks2 , 1CFSAN/NCFST, FDA, Summit-Argo, IL, 60501, 2NCFST, Illinois Institute of Technology, Summit-Argo, IL, 60501
Background: The use of allergen detection methods helps to ensure the absence of undeclared allergens in foods as well as to validate/verify allergen control measures. Many commercially available ELISA kits employ antibodies that are reactive to all protein components in allergenic foods; others use antibodies that are specific towards single allergenic components or marker proteins.This study compared the performance of both types of test kit for detection of heat-treated egg proteins.
Methods: NIST whole egg powder standard reference material #8415 was heated in the presence of water at 60 and 100°C or was dry-heated at 60, 100, 120, 176, 232 and 400°C for 10 min. The amounts of extractable proteins in the heated samples were assayed using the BCA method as well as two commercial ELISA kits.
Results: Elevated heat treatment resulted in a lower level of proteins being extracted. Boiling resulted in more than a 70% decrease in the amount of extractable proteins whereas dry heating at 100°C did not affect the solubility of egg proteins.While the decrease in the amount of extractable proteins in dry-heated samples was generally reflected in the readings observed using both test kits, the change in the amount of extractable proteins in the boiled samples was not proportionally indicated in either test kit. The Neogen Veratox® kit, which is reactive to whole egg proteins, underestimated the amount of residual proteins in boiled samples.On the other hand, the Tepnel Biosystems Biokit® assay, which employs antibodies specific to a heat stable marker protein (ovomucoid), overestimated the amount of protein remaining.
Conclusions: Heat-induced changes in the solubility and structure of proteins need to be considered when commercial ELISA assays are used for the quantification of allergens in thermally processed foods.