Related על ברכות 68:40

One who takes terumah from the threshing floor needs to have in mind (lit., "direct his heart on") what is in the stubble, what is in the straw, what is on the sides, [and] what is on the threshing floor [itself]. One who takes terumah on the winepress needs to have in mind [the volume of] what is in the [discarded] grape skins, and what is in the [discarded] grape seeds. One who takes terumah on an olive tank needs to have in mind what is in the pomace (i.e., the pulp that remains from the olives after the oil is squeezed). If he doesn't intend, it is a stipulation of the court that he takes terumah on the whole.

Rabbi Yosei says, every threshing house is combined into one (see Y. Ter. II.1.11). How is this done? (i.e., how should the threshing house be set up to accomplish this outcome?) One vat for two tanks; two vats for one tank; two vats for two tanks. At a time when everything is combined into one, we take terumah and tithes from one on the other. [If] one of them becomes impure, one takes terumah from the pure that is in it (i.e., in the threshing house) on behalf of the impure that is in it. [If] they are not combined together, one may not take terumah and tithes from one on behalf of the other. [Thus, if] one of them becomes impure, one may not take terumah from the pure that is in it on behalf of the impure that is in it. And similarly, Rabbi Yehudah says, the whole olive press is combined into a single beam. How is this done? One beam for two tanks, two beams for one tank, two beams for two tanks (see Y. Ter. II.1.13). At a time that the whole [olive press] combines as one, we take terumah and tithes from one on behalf of the other. [If] one of them becomes impure we [may] take terumah from the pure on behalf of the impure and tis in it. [If] they are not all combined into one, we may not take terumah and tithes from one on behalf of the other. [Thus, if] one of them becomes impure, one may not take terumah from the pure that is in it on behalf of the impure that is in it.