Many Worcestershire sauces contain anchovies.

 

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From the OU:

Many Worcestershire sauces contain anchovies. Is it permissible to add Worcestershire sauce to meat?

We noted in the past Halacha Yomis that there is a dispute whether fish is nullified in 60 parts. The OU follows the lenient position. As such, Worcestershire sauce that contains anchovies at a ratio of 1:60 may be labeled OU, without a fish designation. However, if the anchovies are more than one part in sixty of the sauce’s components, the product must be labeled OU-Fish.

The question remains whether it is permissible to intentionally add an OU certified Worcestershire sauce, which contains a small percentage of anchovies, to a meat dish? With respect to non-kosher foods, bitul only applies after the fact, should an accidental mixture occur, but it is not permissible to intentionally effectuate bitul (in the words of Chazal, ain mivatlin issur lichatchilla.)Does the same apply to fish, such that it would be prohibited to intentionally introduce fish to a meat dish at a level where the fish would be batel? One can argue that fish is not a prohibited item, but rather a food that poses a danger. Nullification removes the danger and therefore it may be permissible to intentionally nullify the fish component. Rav Elyashiv, zt”l (quoted in P’ninei Ish) maintains that one may in fact add a small amount of fish to meat. As such, one may intentionally add OU certified Worcestershire sauce to a meat dish and consume the final product. This is particularly the case with Worcestershire sauce, since the anchovies were already batel in the sauce itself.

For simplicity’s sake, some companies prefer to label all their Worcestershire sauces with an OU-Fish symbol regardless of whether the amount of fish is nullified or not, and the OU accommodates such requests. One may contact the OU office at kosherq@ou.org to inquire if the amount of fish in a specific brand of sauce which bears an OU-Fish logo is indeed nullified.