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?