The Chafetz Chayim, as we saw yesterday, ruled in his Bei’ur Halakha (to 455:5) that if some salt was mixed with matza dough before baking, the matza may be eaten on Pesach. Although the Shulchan Arukh codifies the custom to avoid adding salt to the matza batter, and the Rama rules that if this was done, the matza may not be eaten on Pesach, the Chafetz Chayim gave several reasons to permit such matza, including the fact that many authorities dispute the Rama’s ruling, and the likelihood that the Rama does not refer here to seasalt.
Other Acharonim, however, accepted the Rama’s ruling and forbade eating on Pesach matza that had been baked with salt. These include Rav Shneur Zalman of Liadi (the Ba’al Ha-Tanya), who writes explicitly in Shulchan Arukh Ha-Rav (vol. 3, 455:30) that one may not eat such matza, in deference to the opinion among the Rishonim that salt causes the dough to leaven.
This ruling of the Shulchan Arukh Ha-Rav is cited as an authoritative source by Rav Avraham Borenstein of Sochatov, in his Avnei Neizer (532), where he addresses the question concerning sugar that mixed with flour. The case under discussion involved wheat that was stored in bags that had been previously used for sugar, and which thus contained some residual sugar. The question arose as to whether this flour, which had a small amount of sugar mixed into it, may be used for baking matza for Pesach. Rav Borenstein, interestingly enough, considers equating this case to the case of salt added to batter before baking. He notes a source cited by the Minchat Chinukh (119) claiming that the obligation to salt sacrifices before they are offered on the altar could be fulfilled by adding sugar, which shares certain properties as salt. Although Rav Borenstein dismisses out of hand such a possibility, he writes that the basic premise, that sugar has properties resembling those of salt, may be correct and relevant to this question regarding matza. He further notes the startling account of Rav Yaakov of Lisa (the Netivot) using sugar, instead of salt, to drain the blood of raw meat, believing that sugar is equivalent to salt in this regard. If, indeed, we may draw a halakhic equation between sugar and salt, Rav Borenstein writes, then we should conclude that flour with which some sugar had been mixed may not be used for matza on Pesach, in accordance with the stringent ruling of the Shulchan Arukh Ha-Rav. In his conclusion, Rav Borenstein writes that scientists need to be consulted to determine whether sugar indeed triggers a process of fermentation in flour as salt does.
Regardless, it is clear that Rav Borenstein did not follow the Chafetz Chayim’s lenient ruling, and maintained that matza that had been baked with salt should not be used on Pesach.