Shailah of the Week by Rabbi Zvi Nussbaum

Rabbinic Coordinator, Kosher Hotline Administrator for the Orthodox Union

Is it tochein to make guacamole at home on Shabbat? 

One of the thirty-nine forbidden melachot of Shabbat is tochein (grinding).

The prohibition of grinding involves reducing any item grown from the ground (and according to some, even some foods that are not grown in the ground such as meat) into small particles. A prime example would be grinding kernels of wheat into flour. Also included is dicing vegetables into small pieces.

This prohibition is not limited to food. Chopping wood into splinters or cutting boards and producing sawdust is also included. 

So, can one mash avocados into guacamole? Is it considered grinding since avocado, though pulverized, does not break apart into distinct units, but remains one mass? 

The Chazon Ish ruled that mashing is tochein, and prohibited on Shabbat. However, it is permitted if one adheres to the following guidelines. 

• The mashing must be done right before the meal.

• The action is performed in an abnormal manner, such as mashing with the handle of a knife.

On the other hand, Rav Moshe Feinstein, zt”l, (Igerot Moshe) was of the opinion that mashing is not tochein, since the banana or avocado remains a single mass, just with a softened texture. Still, Reb Moshe Feinstein ruled that it should only be done as close to the meal as possible.

Obviously, when possible it’s best to prepare guacamole ahead of time, prior to Shabbat (a dash of lemon juice can prevent the guacamole from turning colors). If you forgot to do so, a rabbi should be consulted as to which opinion you should follow for mashing guacamole on Shabbat.