We may not separate stalks of grain as terumah for kernels of grain, olives [as terumah] for oil, or grapes [as terumah] for wine. If one made such a separation, it is not effective. This is a decree [enacted] lest one cause the priest to undertake the difficulty of treading [on the grapes] or pressing [the olives].
One may, however, separate oil as terumah for olives that are being pickled or wine as terumah for grapes that are being dried as raisins. What does this resemble? To separating terumah from two species that are not considered kilayim, separating from the good for the bad.
Similarly, one may separate terumah from olives from which oil will be squeezed for olives that will be pickled, but not from olives that will be pickled for olives from which oil will be squeezed. [One may separate terumah] from wine that has not been boiled for wine that has been boiled, but not from [wine] that has been boiled for [wine] that has not been boiled. [One may separate terumah] from [wine that is] clear for [wine that is] not clear, but not from [wine that is] not clear for wine [that is] clear.
[One may separate terumah] from a specific number of fresh figs for a specific number of dried figs and from a measure of dried figs for a measure of fresh figs, but not from a measure of fresh figs for a measure of dried figs, nor for a specific number of dried figs for a specific number of fresh figs. [The rationale for all the above is that] one should always separate terumah in a generous manner.
One may separate terumah from kernels of wheat for bread, but not from bread for kernels of wheat according to the appropriate calculations. In all the above situations, if one separated terumah [when it was stated that one should not], the separation is effective.