Cold Pressed and Wood Pressed Oils

Wood pressed oil is the oldest way of pressing seed in South Asia. In Tamil it is marachekku ennai, and in the north the same slow method gives kachi ghani oil, a name most often seen on mustard oil. The press is a large wooden mortar with a heavy wooden pestle that turns inside it, grinding groundnuts, sesame or mustard seed against the walls. It works slowly, so the seed stays at a low temperature, and the oil is left to settle and filtered through cloth. Nothing is bleached, deodorised or refined. Cold pressed is the wider term for oil pressed without added heat, whether in a wooden press or a modern expeller kept cool, and virgin coconut and extra virgin olive oil belong here for the same reason.

Unrefined oil looks and behaves differently from the refined oil in most kitchens. It is darker and sometimes cloudy, and a little sediment at the bottom of the bottle is normal. Groundnut oil smells of roasted peanuts, sesame oil is nutty, and mustard oil has a sharp heat that catches the back of the nose. These oils start to smoke at a lower temperature, so use them for tempering, dressing, drizzling and gentle cooking, and keep a refined oil for deep frying, where a neutral taste and steady heat matter more. Many Bengali and Punjabi cooks heat mustard oil until it just begins to smoke, then let it cool a little before the spices go in, which softens its bite.

Each region reaches for its own oil. Gingelly or sesame oil, nallennai, goes into Tamil kuzhambu, onto idli podi and into the pickle jar. Mustard oil fries fish for shorshe maach in Bengal, is stirred raw into aloo bhorta, and tempers sarson ka saag and achar in Punjab. Coconut oil finishes avial and thoran in Kerala and fries the curry leaves for a Sri Lankan curry. Wood pressed groundnut oil is the everyday cooking oil across Andhra Pradesh, Tamil Nadu and Gujarat, and extra virgin olive oil suits salads, bread and a drizzle over roasted vegetables.

Store these oils in a cool, dark cupboard away from the hob and the window, with the cap closed tight, and pour with a clean, dry spoon or spout. Unrefined oil turns stale sooner than refined, so buy a size you will finish and use it within the date on the bottle. Virgin coconut oil sets solid in a cold kitchen; stand the jar in warm water to loosen it. For refined cooking oils and ghee, see the full oils and ghee department.