halacha - Minimum amount of food for Beracha Rishona

I've heard much discussion about minimal amounts of food to qualify as eating (eg. this discussion about how much Matza to eat at the Seder).

How much would one need to eat in order to say a Beracha Rishona (HaMotzi, Mezonot, HaGafen, HaEitz, HaAdama, SheHaKol)? Would even the tiniest little crumb of food need such a Beracha, or perhaps only something more substantial where one is really getting some benefit? A single sprinkle or a tiny swig of juice doesn't seem so significant that it would qualify as "eating". Someone (not a rabbi) once told me that they thought one had to eat at least an olive's bulk of food. Is this so?

Answer

While the Kol Bo (Siman 24) writes that such a small amount would not need a Beracha Rishona, and Rabbeinu Yonah (Brachot 27Rb) writes that for such small amounts every food gets the Beracha Rishona of "SheHaKol", the vast majority of Rishonim and all Acharonim rule that even the smallest amount ("כל שהוא") of food needs its regular Beracha Rishona and there is no minimum amount for a Beracha Rishona (Tosfot Berachot 39a, Rambam Berachot 3:12, Tur OC 210, ShA ibid :1, Arukh HaShulchan ibid., Yalkut Yosef ibid., Mishna Berura ibid. sk 3, Chayei Adam 49:6, Kitzur Shulchan Arukh 50:1, etc.).