The second step is crushing the olives into a paste. The purpose of crushing is to tear the flesh cells to facilitate the release of the oil from the vacuoles. This step can be done with stone mills, metal tooth grinders, or various kinds of hammermills.
Mixing the paste for 20 to 45 minutes allows small oil droplets to combine into bigger ones. It is an indispensible step. Contrary to others that heat or add water to the paste during this process to increase the yield, we don’t apply this method because it results in lowering the quality of the oil. The most common mixer is a horizontal trough with spiral mixing blades. Longer mixing times increase oil yield but allows a longer oxidation period that decreases shelf life.