Is It Permissible to Use Spray Whipped Cream from a Can on Shabbat?
Shailah of the Week by Rabbi Zvi Nussbaum
Rabbinic Coordinator, Kosher Hotline Administrator for the Orthodox Union
Rav Belsky zt"l said that one may not spray whipped cream from a can on Shabbat, because by doing so one changes a liquid into a solid.
There is a discussion among poskim as to whether one is permitted to make ice on Shabbat (e.g. place trays of water in the freezer to make ice cubes). Sefer Dovev Meisharim was strict and did not allow this. He considered the freezing of water into ice to be creating a new entity and said that it is forbidden to deliberately cause this change on Shabbat. Others did not permit making ice cubes on Shabbat because they compared this to building.
However, there were other poskim who were lenient. Rav Shlomo Zalman Auerbach argued that although it is forbidden to crush ice to create water, that is because it is viewed as a positive accomplishment. However freezing water is viewed as a negative accomplishment since one must dissolve the ice back into water to drink the water. That is not the case with whipped cream. Since whipped cream is an improvement from liquid cream, it should not be done according to all opinions.
Rav Schachter disagreed. Since the whipped cream will not remain a solid but will dissolve back into a liquid on its own, he does not view this temporary state to be a change.