In this study we analysed for peanuts in processed foods using an enzyme-linked fluorescent immunoassay
(ELFA), and compared the results with labeled ingredients. Crude peanut protein (CPP) was immunized into rabbits to
produce specific antibodies(Ab). A sandwich ELFA was established using anti-CPP Ab and Ab-horseradish peroxidase
(HRP) conjugate. The cross-reactivities of the Ab toward CPP, peanuts, almonds, soybeans, and walnuts were 100, 9.8,
1.1 ?10-2, 4.4 ?10-3, and 0%, respectively. The samples included 19 items consisting of biscuits, snacks, chocolates, and
so on. The results from the sandwich ELFA showed that peanuts were contained in 7 of the processed food items, among
which, 5 items were labeled as having peanuts present but 2 items were not. One of the 2 items that was peanut-detected
but unlabeled was a biscuit labeled to contain almonds and assayed to contain 2.1?0-3% peanuts, which might have been
due to the weak cross-reactivity of the Ab toward almonds. The other item was a snack labeled to contain soybeans and
assayed to contain 0.098% peanuts, which might have been due to peanut cross-contamination during processing, since the crossreactivity
of the Ab toward soybeans was very weak. These results suggest that ELFA is a good tool to detect peanuts in
processed foods, and allergens in certain processed foods should be labeled correctly.