“Rabbi, two jars of ketchup were sitting on my counter. Suddenly…”
The halachic dispensation of bitul b’shishim (nullifying [a forbidden element] by sixty times to one) does not extend to an ingredient that is milsa d’avida l’taama (something added to provide taste) or derech asiyaso b’kach (a regular ingredient in the recipe).* Therefore—on both counts—if a small amount of non-kosher spice or non-kosher ketchup was added to food, it renders the food assur mi’d’rabbanan (forbidden by Rabbinic decree), regardless of the ratio.
It Could Have Been the Kosher one
What if the cook has two bottles of ketchup, or two identical spice jars—one is kosher and one was found not to be—and unthinkingly adds a squeeze or a pinch of ketchup to a simmering pot, but is not sure if he added the non-kosher or kosher seasoning? If the food in the pot is found to be sixty times more in volume than the non-kosher ingredient, then the prohibition is only of a Rabbinic nature. Since there is uncertainty whether the added ingredient was kosher or not, we apply the principle of sfeika d’rabbanan l’kula (a doubt associated with Rabbinic law is ruled leniently). The food in the pot is muttar (permitted) on the assumption that the kosher ingredient was used.
It May Have Been Margarine
Similarly, a cook has two types of butter available, dairy and vegetable based (aka margarine), and is not sure which was used to grease a chicken dish. Since the issur of mixing poultry and dairy is of rabbinic origin (in contrast to meat and dairy, which is assur min haTorah—prohibited by the Written Law), it can be assumed that the margarine is cooking with the chicken and not the butter. But there are poskim who posit that the gezeirah d’rabbanan (Rabbinic decree) forbidding consuming poultry with dairy should be treated more stringently (the gezeirah having been enacted due to the resemblance of poultry to meat, we should regard chicken-with-a-bit-of-butter as strictly as meat-with-a-bit-of-butter). In practice, if there is a hefsed merubah (significant loss) were the dish to be discarded, the food is muttar.
The Twin Pot Problem
This logic does not apply if there is a certainty of issur in the end-product: the non-kosher seasoning or the butter-chicken mixture occurred in one of the two pots of food for sure, but it is not known which one. Here the uncertainty is not whether the contents became assur, but only which pot of the two. In this case, without being able to clarify which one became non-kosher, the contents of both pots are considered assur.
Another Case of Confused Crocks
However, here’s another possible scenario: One of the pots was rendered non-kosher with a small amount of non-kosher ketchup/seasoning (or dairy butter mixed with chicken). Then the pots were moved, or the cook stepped out for a moment while the seasoning or butter was added a second time. Now it is uncertain if it was indeed the second pot that became assur, or perhaps the circumstances of similar pots or a busy or absent cook caused the seasoning to be added twice to a single pot. There is a principle of tolim kalkalah b’mikulkal (we assume the “spoilage” occurred to the one which is already ruined) with regard to an issur d’rabbanan; it can be assumed that the second helping was added to the same pot as the first one—and the second pot is muttar.
This principle would not apply in reverse: If it is certain which pot received the non-kosher ingredient the second time, it cannot be assumed that it was also the first time, and in that case—as in the other scenario of two pots mentioned above—the contents of both pots are considered assur.
(It should be noted that these conclusions apply to the specific scenarios cited in this halachah. Minor details can change the psak—ruling, so if a cook is unsure if the issue at hand is identical to these circumstances, a rav should be consulted. In addition, the muttar status in these cases is for the food itself. The utensils used in the mix-up may require kashering, if possible.)
*See Halacha #536 for a list of bittul b’shishim exclusions.