Can the mitzvah of tzedaka be fulfilled by nesina, giving, if the recipient cannot do a kinyan to accept? Nafka minah if the recipient is a katan, a shoteh, or even a woman (mah she’kansa isha kanah ba’aleh means everything you give to her would revert to her husband’s possession and he might not need the money). R’ Elchanan raises this chakirah in the end of Koveitz He’Oros in the aggadita section.
A am a bit confused as to why he cites this sugya as relevant. Nedarim 34b raises the question of whether a neder of “kikarei elecha” would prohibit the mudar from eating the kikar of bread if it is given to him by the madir as a gift – do we say that once the kikar leaves the madir’s possession it is not longer “kikari”, his kikar, and it becomes permitted? The gemara first argues that it is obvious that the kikar is assur even if given as a gift. While in the madir’s possession and under his control, there is no need for a neder to prevent the mudar from eating the loaf. The whole point of a neder is to prohibit the kikar from being eaten even after it leaves the madir’s possession. However, the gemara rejects this reasoning. Perhaps the neder may have been taken to prevent the mudar from eating the kikar even while it remains in the madir’s possession, e.g. the mudar is invited for a meal.
I am not sure why R’ Elchanan needed to cite this gemara to prove what seems to be a simple point: one can give benefit to someone without actually being makneh anything to the recipient. What remains unclear (and R’ Elchanan acknowledges that this gemara does not resolve the dilemma) is whether such benefit fulfills the mitzvah of tzedaka or whether (though it may be a chessed) the mitzvah of tzedaka requires a formal act of kinyan.