About half of the flesh (kernel) inside the shell of a good quality properly dried walnut is oil. There can, of course, be significant variations depending on growing conditions in a particular region and also from season to season. Different varieties (cultivars) of walnuts also vary in oil content.
The European traditional way of making walnut oil is to grind the flesh (which has to be very good quality) into a paste, often using large stone wheels to do so.
The paste is then roasted, the method and amount of roasting making a significant difference to the finished product. Roasting above a certain temperature will maximise oil extraction and minimise the chances that any vitamins survive. After roasting the paste is pressed, usually in an hydraulic press. The quality of the resulting oil depends on the roasting time and temperature and on the pressing conditions. Wellwood cold pressed walnut oil is not roasted and is produced on a screw press. This method extracts less oil than the traditional method and results in an oil with a delicate nutty flavour which is most attractive.
After harvesting the walnuts are dried. Some are selected for sale in-shell and most are cracked. Immediately after cracking they are vacuum packed to retain maximum freshness until we are ready to make a batch of walnut oil. We also vacuum pack walnuts for sale. When sufficient nuts have been cracked and packed they are cold pressed using a continuous screw press method. The resulting oil and fines are stored in stainless steel drums in our cool room to allow the fines to settle.
The walnut oil is then bottled, labelled and packed on the premises. There are absolutely no additives of any kind whatsoever added to the walnut oil. It remains pure and is not refined and is normally not filtered, so there may be a little sediment at the bottom of a bottle. We believe the unfiltered oil has a slightly better flavour than the filtered product.