When something that is not kosher gets mixed in with kosher food, what is the status of the mixture?
According to Jewish law, if the amount of kosher food is so overwhelming that the non-kosher food does not affect its taste, we apply the concept of bittul – nullification – and the food is deemed kosher.
- kefeila – by having an expert, non-Jewish cook taste the food
- shishim – by measuring the mixture and ascertaining that there is 60 times more kosher food than non-kosher food.
Different suggestions are offered to explain why we rely on a non-Jewish expert cook in this case, while we ordinarily only trust Jews with regard to issues of kashrut.
Rashi explains that we distinguish between a situation like this one where we approach him with a question and cases where he comes on his own initiative. In the latter case we suspect that he has some personal interest in the information that he is sharing; in our case we view him as someone who is simply sharing information – meisi’aḥ lefi tumo – and can be trusted.
The Ran argues that the crucial factor in this case is his expertise. He will not ruin his reputation as an expert regarding food in order to fool us about the taste, so he can be trusted.
Another disagreement revolves around the role that the kefeila – the expert cook – can play. Although Tosafot rule that as soon as the kefeila announces that the mixture is free of any non-kosher taste, it is deemed to be kosher and can be eaten, Rashi argues that having the kefeila taste the food is a stringency, and that unless there is also 60 times more kosher food, the mixture is still forbidden.
Practically speaking, the Rema rules that today we no longer rely on expert tasters and that in the case of such a mixture we would check to see whether the volume of kosher is 60 times that of non-kosher if it is to be deemed permissible.