Reference for Terumot 1:8
אֵין תּוֹרְמִין שֶׁמֶן עַל זֵיתִים הַנִּכְתָּשִׁין, וְלֹא יַיִן עַל עֲנָבִים הַנִּדְרָכִים. וְאִם תָּרַם, תְּרוּמָתוֹ תְרוּמָה, וְיַחֲזֹר וְיִתְרֹם. הָרִאשׁוֹנָה מְדַמַּעַת בִּפְנֵי עַצְמָהּ, וְחַיָּבִין עָלֶיהָ חֹמֶשׁ, אֲבָל לֹא שְׁנִיָּה:
One may not set aside <i>Terumah</i> from oil for crushed olives, nor from wine for trodden grapes. If one has already set aside <i>Terumah</i>, one's <i>Terumah</i> is [valid] <i>Terumah</i>, but one must again set aside <i>Terumah</i>. The first [set of <i>Terumah</i>] will render on its own [another substance that it falls into] <i>Demai</i> [produce from which it is uncertain if tithes are already taken] and requires a fine of a fifth [of its value if eaten by an Israelite], but not so with the second [set of <i>Terumah</i>].