During the process of oil extraction, the seeds are crushed using pressure. The pressure exerted causes the temperature to rise, which causes the seeds to lose the goodness of its nutrients and taste. In cold pressing or wood pressing, a traditional wood churner (referred to as Marachekku) is used to crush the seeds and extract the oil. Even though the friction causes the temperature to rise, the slow, mechanical process ensures that the temperature does not go beyond the room temperature. This helps in the retention of the goodness of the oil.
However, in machine pressed oils, the expeller machine that is used to crush the seeds cause high rise in temperature, leading to loss of valuable nutrients of the oil.