The Rema (YD 99:6) rules that if milk fell into water and was nullified in it, and afterwards that water fell into a pot of meat, even if there are not 60 parts of meat per part of milk, since the milk has been nullified in the water, the mixture is permitted.
The Shakh adds that one may even intentionally use the water with meat, since the milk has already been nullified by the water. However, some acharonim claim, one may not add milk to water with the intention of adding that water to meat.
If so, it would seem that one may intentionally fry meat with margarine that contains 1% milk! Similarly, it would seem that one may use non-stick sprays marked "dairy," if their dairy content is less than one sixtieth of the content of the spray, for frying meat! If so, one may question why the product is marked "dairy" at all?
The OU, for example, in an email response to an inquiry (6/17/00), explained their policy.
This the OU's Policy. When a manufacturer wishes to add an ingredient where the dairy component had become batel, he can get a Pareve Status for his product. But a company producing a product where the recipe calls for a tiny drop of dairy among vastly more of Pareve ingredients, he wants to be "mevatel le-khatchila" the drop of dairy - that is halakhically not permitted. Which is why such products get the OU-D designation.
One may wonder whether the consumer should ALSO be considered a "mevatel," i.e., one who is intentionally nullifying, since he is using a product to which milk was intentionally added, along the lines of adding milk to water in order to add it to a mixture of meat, which most poskim prohibit.
In any case, certainly "be-di'avad" the food (and utensils) may be used. One should consult a rabbinic authority regarding the intentional use of such margarine or non-stick sprays, although such a practice would seem to be inappropriate due to the confusion it may cause.
