When we discuss the prohibition of eating forbidden foods, it is important to note that only foods that are edible will make a person liable for punishment if he eats them. In the event that the food has spoiled and is no longer fit for human consumption, then the usual prohibition would not be in force. This law – noten ta’am lifgam, mutar – has its source in nevelah, i.e. meat that has not been slaughtered properly that is forbidden. The Torah teaches (see Devarim 14:21) that nevelah cannot be eaten, rather that it should be given or sold to a non-Jew. From this we deduce that nevelah only needs to be given away or sold if it is edible; if it is not edible, then there is no prohibition attached to it.
A classic example of noten ta’am lifgam is the case of pots that were used to cook non-kosher food, and we assume that the pot itself absorbed some of the taste of the forbidden food. In such a case, as Rav Huna bar Ḥiyya points out, we assume that any taste that was absorbed remains only for a day. Once the pot is an eino ben yomo – the taste in the pot is more than a day old – any taste that might transfer from the pot is considered bad, and will not be considered significant. According to Rav Huna, when the Torah required the people in the desert to place pots captured from the Midianites through fire to remove all taste from them (see Bamidbar 31:23), that requirement applied only to those pots that had been used within the last day. All others may have been subjected to the same treatment, but only for reasons of safek – of doubt – because of the possibility that they had been used so recently.