(a) The Tana permits separating Ma'asros from oil on olives that have been pickled in wine or in vinegar. The fundamental difference between pickled olives and pounded ones (which the previous Mishnah forbade) is - that the former is considered Nigmerah Melachto, whereas the latter is not.
(b) 'Nigmerah Melachtan' means - that it has reached the stage when it is ready to be Ma'asered.
(c) The Mishnah also permits - separating wine on grapes that have been designated for making raisins.
(a) One is permitted to Ma'aser olives or oil on olives, or wine or grapes on grapes, that have been designated for eating.
(b) Consequently, says the Mishnah, even in the event that the owner then changes his mind and decides to use the olives to produce oil or the grapes to produce wine - it is not necessary to Ma'aser them again ...
(c) ... since the first separation was one hundred per cent legal.
(a) The Mishnah forbids the separating of Ma'asros from something which the Tana describes as 'Davar she'Nigmerah Melachto' on something which is not. A 'Davar she'Nigmerah Melachto' with regard to corn is - after the 'Miru'ach' (flattening of the pile that forms after winnowing) has been performed ...
(b) ... and the same ruling applies to the reverse case (where he separates a Davar she'Lo Nigmerah Melchachto on something which is Nigmerah Melachto').
(c) The Tana learns from the Pasuk in Korach "ka'Dagan min ha'Goren ve'cha'Melei'ah min ha'Yekev" - the Limud that we just discussed.
(d) If one contravened this ruling and Ma'asered from one on the other - the Terumah is valid Bedi'eved ...
(e) The one dual exception to this ruling is - someone who separated from olives on oil or from grapes on wine, where the Tana hold 'Ein Terumasan Terumah' (since he causes the Kohen a loss, as we learned above).