Tochen

Definition

1. The prohibition of Tochen (grinding) includes cutting whole objects into small pieces, crushing, mashing, or the like.
2. Tochen also applies to non-foods for example it's forbidden to crush a clod of dirt, shave splinters off a piece of wood, sawing wood with intent for the dust.

Appliances

1. Any tool which is designated for crushing or the like such as a mortar or a knife used only for dicing may not be used in any manner even if it doesn't involve any prohibition of Tochen.
2. One may use an egg slicer (row of metal strings which slice an egg when pressed) but one should not use an onion slicer (a machine which is made of a set of knifes that surrounds the onion and dices it).
3. One may cut bread in a machine (manual, non-electric) which cuts slices of bread.

Raw fruit or vegetables

1. Raw fruits or vegetables may not be crushed or cut finely but only may be cut in slightly large pieces. One should also be careful to only cut it into large pieces right before the meal.
2. For a child or someone who can't eat large pieces there is what to rely on to cut it up into small pieces as long as one does so right before the meal.
3. It's forbidden to crush a banana or avocado unless it's already so soft that when one pulls a part of the fruit, that part separates from the rest of the fruit.
4. One may not crush a banana or tomato even if afterwards it while remain a cohesive mush. For someone whom it is hard to eat such food it is permissible as one does a Shinui (change) by using a spoon or the back of the fork and not the prongs of the fork which are usually used during the week.

Cooked fruit or vegetables

1. Fruits or vegetables which were cooked to the point that it's easy to crush may be crushed on Shabbat.
2. Potatoes or vegetables which were cooked may not be put through a strainer in order to puree it (as the strainer is designated for that purpose) but one is permitted to crush it with a fork (even the prongs) as long as it was cooked to the point that it's easy to crush.

Pre-crushed food

1. Food which was made from crushed particles may be crushed on Shabbat (not using a utensil designated for crushed but rather a regular knife) if one is going to eat it on Shabbat. For example one may crush matza, bread, crackers, chocolate, and sugar.
2. Salt granules which solidified because of a moisture may be crushed on Shabbat, however, one may not crush salt crystals (looking like blocks) or any other spice which has never yet been crushed unless one does two Shinui's (changes) by using the handle of the knife or fork on a plate or the table.
3. Food which was crushed very well before Shabbat or on Shabbat in a permissible may may be further cut on Shabbat even in the normal fashion.
4. One may pur hot water (even from a Kli Rishon) onto farina, rice porridge, or corn flour and mix it around even crushing the clump with a spoon.

Foods which don't grow from the ground

1. Foods which don't grow from the ground such as cooked eggs, meat, or fish may be crushed on Shabbat (not using a utensil designated for crushing) if one plans on eating it that Shabbat.