Related על מעשרות 2:8

One who buys dried figs with the intention of pressing them [into fig cakes], [or] dates with the intention of making them into honey -- Rabbi Meir says, he may not eat from them casually or tithe them as Demai, and the Sages say, he may eat from the casually and tithe them as Demai. Rabbi Meir concedes to the Sages that one who takes ears of corn with the intention of processing them, [or] grapes with the intention of making wine from them, [or] olives with the intention of making oil from them, he may eat from them casually, and the Sages concede to Rabbi Meir that with [respect to] fruits, which do not need to 'finish their work' [to become liable for tithes (see Maasr. 2:4)], that he should not eat from them casually.