Saying “Harei Zu Challah”:
After one separates a Kezayis of dough she is to say “Hareiy Zu Challah” or “This is Challah”.
Bedieved if was not said: If one did not say “Hareiy Zu Challah” but had in mind for it to become Challah, it is nevertheless valid. [If, however, one did not even have in mind for it to become Challah, and simply forgot to say Harei Zu Challah, it is not valid, and the piece must be made into Challah as soon as one remembers. If one talked of unrelated matters in-between the separation and now remembering, the blessing is to be repeated.]
 Rav Akiva Eiger 328:1 in name of Raavad, in name of Rav Acha Gaon; Beis Yosef 228; Rashba Chulin p. 94; See Admur 457:18 “All the sanctifications of Teruma and Maaser is through speech…One calls it the name Challah”; Admur 527 KU”A 2 based on Tosefta in Teruma chapter 3 “Although Terumah is sanctified with thought alone, if one plans to call it a name the food is not sanctified until one does so”
 Admur 4578:18 in parentheses “Or even thought about it alone”; Admur in KU”A ibid; Michaber Y.D. 331:46 regarding Teruma; Implication of Setimas Haposkim who do not mention the need to say Harei Zu Challah
 Admur ibid; Upashut!