Pressed at 100 Bar
In France the production of artisanal walnut oil continues to exist despite the legislation, health and safety regulations and bureaucracy imposed by the European Union. For centuries walnut oil was produced in oil mills, driven by horses, in iron tubs, heated by wood burners and stirred with wooden spoons, filtered with an old cloth ….
In the small town De Saint Cere, rue Croix de Lagarde Nr 55, that tradition is kept alive by two dedicated oil producers, Marcel and Charles. They operate the walnut mill as it was done 100 years ago… and yes you can witness it all from close by. A heaven for those who love old machinery, build in the mid 1800’s installed and operational ever since.
The horse is replaced with a 4PK 400Volts AC tri-Phase central motor which drives the complete mill through a system of flat belts , wheels and pulleys ; a truley amazing technique.
It all starts with 14 Kg of walnuts, removed from their shell. Decanted into a steel riveted tub.
A 600Kg heavy granite stone rolls over the walnuts, rotating on the X and Y-axis… endless circulating and crunching the walnuts for about twenty minutes. It completes with a yellowish paste, with no trace of oil so far.
The walnut paste is scraped into a bucket, every little bit counts and nothing is left to waist even the smallest amount of walnut paste is brushed into the bucket with a twig based brush . Talking about tradition….
Meanwhile, a 1 meter wide steel pan is heated-up , nowadays by a gas burner. So far that is the only modernization, as initially that was heated with wood. The walnut paste is poured into the pan, within a few seconds the air is filled with the pleasant smell of walnuts.
Heating continues until the paste reaches a temperature of 86 degrees centigrade, while been stirred continuously.
The end is near once the paste discolors and turns greyish. By now the temperature is about 100 degree’s. The exact temperature and time determines the final flavor of the walnut oil and is the secret of Marcel and Charles.
The press is a cast iron fixture, driven by water pressure. At the time hydraulic presses did not exist and a ingenious engineered water pomp was used to drive the press. A small concentric axel drives a piston pushing water into the water-based press. The dual steel ball return-valve prevents the pressurized water to revert.
The press is fitted with a piece of cloth used as a filter and several metal plate inserts to channel the pressed walnut oil .
The warm walnut paste is decanted into the press, and pressurization can start. Slowly the pressure builds up, at about 50Kg/cm the first drips of oil appear at the lip.
While pressure builds up, more oil erupts filling the metal bucket.
Time for a taste, yes I know its a bit cheap with a plastic spoon. Never the less, Martine experienced an explosion of walnut flavor gently stroking mouth and tongue… as she stated, “ I never tasted such a delicious and voluminous rich flavor “.
At 100Kg/cm, the walnut past reaches its oil release peak , slowly shrinking until the flow stops.
By now seven liters of golden brown walnut oil fills the bucket ready for consumption. As throughout the whole process, nothing is wasted and even the smallest amount of oil is recovered out of the press gutters with a sponge.
The press is depressurized, the piston retracts and the residue walnut paste is knocked out with a hammer as it formed a heavy and dense substance under the heavy pressure.
Remember that 100Kg/cm pressure was placed per square centimeter. The press piston is about 40 cm in diameter, producing easily 1.256 Ton of pressure.
The residue is used for animal food and some new wave cooking gurus call it walnut flour used in bakery.
If you are ever in France, try to visit Marcel and Charles.
Thanks for reading, Steve