Traditional walnut oil

In some parts of the Alps-Valle d’Aosta, the French Rhône Alps and the northwestern Swiss cantons-the extraction of
walnut oil is still common practice today. This reflects the widespread tradition of producing plant-based oils other than olive oil, characteristic of the countries north of the Alps.
These oils were cheaper than butter, and the use of walnut oil in the kitchen has a long history. Known and appreciated by the Romans, during the Middle Ages it was used as both a food and a lamp fuel. One of the oldest surviving mentions of cooking with walnut oil in Switzerland dates back to the 16th century. The documents are stored in the archives of the city of Neuchâtel, in the French-speaking canton of the same name, one of the oil’s historic production areas. The documents describe two types of walnut oil: a small production of cold-pressed oil used by nobles, and a hot-pressed oil destined for lower social classes and the production of medicines. The hot extraction produced higher yields and gave the oil a pleasant toasted, fruity note. For these reasons it became the only production technique common in Switzerland in the early 20th century and later between the two wars.
After the Second World War the consumption of walnut oil fell dramatically, as food technology brought cheap butter, margarine and other vegetable oils to the market. The cultivation of walnuts and the laborious harvesting, drying and shelling of the nuts were abandoned by farmers, surviving only as a marginal, supplementary activity for families. Currently the production of hot-pressed walnut oil is carried out by a few mills, dotted around the cantons of Vaud, Bern, Solothurn, Aargau and Zurich.
The dried nuts are picked over, shelled, ground and then baked in the mill’s wood-fired oven at a temperature over 120°C.
The ground nuts are stirred continuously for 30 minutes, so that they cook evenly. The resulting mass is then wrapped in two cloths, an internal one made from cotton or polythene and an external one of jute, and placed in a press. During the pressing, the external layer of jute holds a little of the pressed oil and ensures its slow release. The extracted oil is very aromatic, with pronounced toasted notes. The mass that remains inside the press, the nillon, is dried and used as a flour to make cakes, or further pressed to make a crunchy sweet given to children.