1. A single food as in the case of eating a significant amount of non kosher steak or a pork chop by themselves. Clearly the person has enjoyed a non kosher food and has violated the prohibition of eating a maachal assur.
2. Eating a food as a part of a dish. According to halacha it is not necessary to eat a food in isolation to have a non kosher experience. As long as it constitutes a significant proportion of a dish, Halacha views each ingredient as a distinct eating experience in its own right. The concentration an ingredient needs to have to be considered substantial is a “kezayit bichdei achilat peras” enough to have consumed an olive’s worth of the ingredient within a few minutes worth of eating the overall dish.
If one eats ham and eggs and there is enough ham to have eaten a “kezayit bichdei achilat peras” one is considered as actually eating two distinct foods simultaneously. One is considered to have had eaten ham as well as having eaten an egg. This kind of simulataneous activity is considered a full fledged prohibition of eating a maachal assur.
ג כיצד הוא ממשו, כגון שהיה מן החלב כזית בכל שלוש ביצים מן התערובת. אם אכל מן הגריסין האלו כשלוש ביצים--הואיל ויש בהן כזית מן החלב, לוקה: שהרי טעם טעם האיסור, וממשו.
If one eats less than a “kezayit bichdei achilat peras” one is considered to have eaten a dish which contains a non kosher flavoring. This is not considered a distinct eating experience of a non kosher food and is not prohibited from the Torah.
In the case of Chametz, we find an exception to this rule. The uniqueness of Chametz expresses itself in two distinct if somewhat related ways.
ו אין חייבין כרת, אלא על אכילת עצמו של חמץ. אבל עירוב חמץ כגון כותח הבבלי ושיכר המדי, וכל הדומה להן מדברים שהחמץ מעורב בהן--אם אכלן בפסח, לוקה ואין בו כרת: שנאמר "כל מחמצת, לא תאכלו
1. In order to violate issur chametz one must eat chametz itself, in isolation without any other food in a dish. Clearly this is unlike any other maachal assur. In other maachalot assurot, eating a dish containing a non kosher ingredient is considered mamashut, a food experience of actual non kosher food, so long as it is of the size of “kezayit bichdei achilat peras”.
2. There is a separate issur of eating chametz in a dish form. There is no counterpart to this in maachalot assurot, one has either eaten a prohibited food, or one has not.
What is more, this prohibition of eating chametz in a dish form requires a measure of “kezayit bichdei achilat peras” the exact measure usually considered to be mamashut, a distinct eating experience of non kosher food in its own right.
How are we to understand this unique formulation of Issur Chametz?