Halakhah sobre Chalá 1:18

Dough of the arnona (tax) - meaning to say that is shared by a Israelite and a gentile - is obligated in challah, if the Israelite's portion constitutes the measurement of [what is required for] challah. Dough that is made for animals is exempted from challah, but if it is for both animals and humans, it is obligated in challah (Mishnah Challah 1:8). If prepared dough - meaning to say, that from which challah had been separated - was mixed with other dough from which challah was not separated, what does he do? A new dough is brought and placed on [the mixture], and he takes challah for all of it. But if he has no other dough, he should take challah from [the mixture]; apparently without a blessing, for all of it has been rendered 'unseparated' (tevel). And even a small amount can render several prepared doughs, 'unseparated'; for 'unseparated' material creates a prohibition with the smallest amount, as I have written in the Order of Emor el HaKohanim (Sefer HaChinukh 284). And the rest of its details are elucidated in Tractate Challah and so [too,] in Tractate Orlah (see Mishneh Torah, Laws of First Fruits and other Gifts to Priests Outside the Sanctuary 5).