One who eats less than a כזית, whether it's from bread or it's from other foods, or one drinks less than a רביעית, whether it's from wine or other beverages, one blesses at the outset of blessing that is fit for that particular type and one does not bless a post-consumption blessing at all. And there are some who are unsure whether to say it's on something that it is like its creation, such as a whole grape or pomegranate seed that one blesses a post-consumption blessing even though there's not an כזית of it. Therefore, it is proper to be careful not to eat something less than כזית . Rema (gloss): And it is not considered a beriah unless it was eaten as-is (in its entirety), but if its seed was removed, it is not called a beriah [Rav Yitzḥak, chapter “Keitzad Mevarchin,” and Beit Yosef in the name of the Rashba] There are also those who are uncertain whether the after-blessing on wine requires a כזית; therefore, it is best to be careful not to drink less than a כזיתor a רביעית.
One who tastes a cooked dish does not need to recite a blessing unless the amount is a רביעית, even if he swallows it. However, some say that if he swallows it, a blessing is required, and they exempt the one who tastes only when he spits it out — in which case, even a large amount does not require a blessing. Rema : And in cases of doubt regarding blessings, we are lenient.