As we have noted, the laws of tum’at okhalin – ritual defilement of food – will only apply if two basic requirements are met –
1. The item must be perceived as food appropriate for human consumption, and
2. The item must have been made wet with one of seven liquids, e.g. water or blood (see Vayikra 11:37-38).
Our Gemara quotes a Tosefta from Masechet Uktzin (3:1) where Rabbi Yehudah relates that Rabbi Akiva taught:
The helev – forbidden fat – of a slaughtered animal, in villages, needs intention to be used for food, but does not need to be made susceptible to uncleanness, since it has already been made susceptible by the slaughtering.
Rabbi Yehudah questioned Rabbi Akiva regarding this ruling, saying:
Master, did you not teach us that if a man gathered olshin, washed them for feeding cattle, and then determined to use them as food for man, they again need to be moistened in order to be rendered susceptible to uncleanness?
Rabbi Akiva then retracted and taught according to Rabbi Yehudah, that the second requirement – washing the item – is only significant if the first requirement – that the item be viewed as food – has already been fulfilled.
Viewing helev as food clearly means that it would be eaten by non-Jews. Rashi offers two explanations as to why in villages helev was not automatically seen as food. His first approach is to suggest that since there are few people in villages and there is no lack of meat, such fats were not ordinarily eaten. According to his second approach, helev was a delicacy, and in villages where most people were poor, few could afford to eat helev.
The olshin referred to by Rabbi Yehudah is Cichorium endivia, a cultivated plant whose blue, white or purple leaves are eaten much the way lettuce is. Today the most common use of this plant is in salads or as the basis for making coffee substitute, but it is often used as livestock feed, as well.