The Poskim discuss whether reciting a Beracha Aharona of Boreh Nefashot cancels the original Beracha. This applies to a case where one explicitly intended to continue eating over an extended period, and he recited the Boreh Nefashot not to signify the end of his eating, but to avoid an interval of 90 minutes since he last ate, which revokes his ability to recite it. This is a common occurrence when people snack throughout the night while learning, such as on Shabuot and Hoshana Rabbah. When they make the original Beracha, they intend to eat and drink continuously, yet they may have to make a Boreh Nefashot in the middle. The question is whether a new Beracha must be recited when he continues eating.
The Meoreh Ohr says a tremendous Hidush: The Boreh Nefashot does not cancel the original Beracha, and he may continue eating or drinking without a new Beracha. The problem with his position is that he does not bring any source or proof for his ruling. On the contrary, the Poskim rebut his position with a proof from the Be’ur Halacha (Rav Yisrael Meir Kagan of Radin, 1839-1933) in Hilchot Pesach. There, the Hafetz Haim explains that the reason one should eat less than a Kezayit of Karpas is to avoid having to make a Boreh Nefashot afterward, which would force him to make a new Beracha of Ha’adamah on the Maror. Thus, it is apparent that the Boreh Nefashot does cancel out the original Beracha. This is the opinion of Hacham Ovadia.
SUMMARY
Even if one made a Beracha with intent to continue eating, he must make a Boreh Nefashot before 90 minutes elapse from his last sip, and that cancels the original Beracha, forcing him to make new Berachot before he continues eating.
