When will a mixture containing non-kosher food be forbidden and when will it be permitted?
Rabbi Abbahu quotes Rabbi Yoḥanan as teaching that when the mixture contains non-kosher food and the taste of the non-kosher food is noticeable, then the mixture is forbidden and the person who eats it will be liable to receive lashes as punishment. If the taste of the non-kosher food is noticeable, but there is no actual food in the mixture – e.g. the non-kosher food melted and cannot be found or it was recognizable and was removed – then it is forbidden, but there is no punishment for eating it. If the taste of the forbidden food is an unpleasant taste – noten ta’am le-fegam – then it is permitted entirely.
According to Rashi, there is no punishment in the case where the taste of the non-kosher food was noticeable but there was no actual forbidden food in the mixture because there is no biblical prohibition in such a case. Other rishonim, however, believe that there are sources in the Torah that forbid such a mixture, but the prohibition is not severe enough to require punishment. One explanation is that every case where there is taste but no actual forbidden food it is impossible to eat a sufficient amount – a ke-zayit be-khdei akhilat peras (an olive-size amount eaten in the time that it takes to eat half a loaf of bread) – to become liable for punishment. This is based on the rule that it is prohibited to eat a ḥatzi shi’ur – a partial measure – of forbidden food, but there will be no punishment until a full measure is eaten within the specified amount of time.
It is a halakha le-Moshe mi-Sinai – a tradition given to Moses on Mount Sinai – that a person is responsible for eating forbidden food not only if he eats it all immediately, but even if a minimum amount was eaten within a prescribed time limit – ke-zayit be-khdei akhilat peras. If he extended his eating over a longer period of time, then it is considered to be two separate acts of eating and he would not be held liable.