We have already discussed several times that regarding the laws of Blessings of Enjoyment recited before eating that there is no limit for reciting a blessing before eating, meaning that no matter what amount of food or beverage one eats or drinks, one must still recite a blessing. The reason for this is because one may not enjoy from this world without reciting a blessing and one enjoys while eating or drinking a small amount. Only with regards to an after-blessing or Birkat Hamazon must one eat the amount of a Kezayit (olive’s volume approximately 27 grams) as we have discussed in the past. To recite a blessing before eating, however, requires no minimum amount to be eaten.
The Gemara (Berachot 14a) states that if one eats a food not for the purpose of eating, rather, one does so merely to taste the food in order to ascertain if it is missing a certain spice and the like, one should not recite a blessing before tasting the food. Only if one tastes the amount of a Revi’it (approximately 81 ml) must one recite a blessing, for in such a case, it does not make sense that one would taste such a large amount of food without also having in mind to “eat” it since one does not require such a large amount just in order to “taste.”
The Rishonim disagree regarding the explanation of the above Gemara concerning one who does not need to recite a blessing before merely tasting a food. According to Rabbeinu Chananel, one who merely tastes a small amount of food is exempt from reciting a blessing before eating only when one spits out the food after tasting it, for since one is not swallowing anything, one need not recite a blessing on the food. On the other hand, according to the Rambam, even if swallows the small amount of food he has tasted, as long as one does not intend to “eat” and is only doing so to “taste,” one will not recite a blessing before eating this food, for our Sages only instated blessings upon foods one eats and enjoys while intending to actually “eat” and not merely “taste.”
Halachically speaking, Maran rules in his Bet Yosef that since the Rif agrees with the opinion of the Rambam and there is an issue of a “doubt regarding blessings,” for according to the opinion that one should not recite a blessing before tasting a small amount of food even if one swallows it, doing so would constitute a blessing in vain, thus, the Halacha follows the opinion of the Rambam that since one does not intend to actually “eat,” one does not recite a blessing before doing so. Maran rules likewise in his Shulchan Aruch.
Maran Rabbeinu Ovadia Yosef zt”l writes that the Tashbetz (Rabbeinu Shimon bar Tzemach, one of the great Rishonim) agrees with the opinion of Rabbeinu Chananel and explains that even according to the Rambam, as long as one swallows that which one has tasted, one must recite a blessing before eating and the aforementioned Gemara which exempts one from reciting a blessing applies only when one spits out the food he has tasted. Several other Rishonim rule likewise. Nevertheless, halachically speaking, the ruling on this matter certainly follows that of Maran Ha’Shulchan Aruch, for we have a great rule that “When in doubt regarding a blessing, act leniently and do not bless.”
Nonetheless, in order to try and fulfill all opinions, it is preferable that before one tastes any given food, one should have in mind specifically to enjoy the food one is tasting and treat it as though one were actually “eating” in which case one would be permitted to recite a blessing before tasting according to all opinions, for one intends to enjoy what he is eating as well. Doing so would save one from any concern of eating without first reciting a blessing.
Summary: If one merely tastes any given food, one should not recite a blessing on the food before doing so (unless one tastes an amount of 81 ml). Nevertheless, it is preferable for one to intend to actually “eat” and enjoy the food while one tastes it in which case one will be permitted to recite a blessing before tasting the food and will have fulfilled all of the various opinions quoted by the Poskim.