OLIVE OIL IN CALIFORNIA 345 



THE MANUFACTURE OF OLIVE OIL 



Olive oil is made in this State with apparatus of both Californian 

 and Europeon design, and, as a rule, there is made only one, and at 

 most but two, pressings of the pomace, which is then used for fattening 

 swine. In the frequent working over of the pomace, and the close 

 extraction of the oil, as practiced in Europe, we have done little as yet. 



Olive oil is made on a small scale by a number of parties who use 

 home-made contrivances, or small, portable cider machinery for the 

 crushing and pressing. During the last few years quite a number of 

 mills have been erected at several points in California and they have 

 made a market for the olives produced by growers who do not care 

 to undertake manufacture. A detailed account of oil making, includ- 

 ing descriptions of buildings and machinery, published by the University 

 Experiment Station has been out of print for several years, but can be 

 consulted in libraries.* As this is available to those who desire such 

 specific information, only an outline will be undertaken for the informa- 

 tion of the general reader. 



Drying. Extraction of oil from fresh olives gives the best oil, 

 but it is somewhat troublesome, and it is customary to partially dry 

 them. This partial drying is also useful to keep the fruit for some 

 time or for shipment before crushing. Place the olives in layers not 

 more than three inches deep, on trays that are stacked in a dry, well- 

 aired room, protected from the wind and the direct rays of the sun. 

 Turn daily until the fruit becomes well wrinkled. This requires about 

 eight or ten days, according to the degree of temperature. The par- 

 tially dried fruit may be stored in a dark room where the temperature 

 does not rise above sixty degrees Fahrenheit, for three or four weeks 

 without any serious deterioration of oil. To hasten the drying process, 

 artificial driers, constructed on the same principle as the fruit or hop 

 driers, are sometimes used. The olives are placed in a single layer 

 upon trays, and the drier is kept at a temperature of about one hundred 

 and twenty degrees Fahrenheit ; at over one hundred and thirty degrees 

 Fahrenheit the quality of the oil may be impaired. The drying takes 

 about forty-eight hours more or less according to the nature of 

 the fruit. 



Crushing. The olives are usually crushed by heavy stone roll- 

 ers revolving in a circular depression in a bed of masonry into which 

 the fruit is placed. Chrushers with corrugated bronze or bronzed metal 

 rollers are now made that perform their work in a very satisfactory 

 manner, breaking up the flesh and pits very thoroughly. As they are 

 all of metal they absorb no oil and are easily cleaned. It is very 

 essential that the flesh should be crushed thoroughly in order to break 

 up the cells and permit the oil to be pressed out. 



Pressing. When the revolving crusher has reduced the olives 

 to a mass, the pomace is shoveled up from the bed of the mill and pre- 

 pared for pressing. Instead of the fabric of woven esparto grass which 

 is used abroad, coarse linen cloth is used. A certain amount of the 



* "California Olive Oil: its Manufacture," by G. W. Shaw, Bulletin 155, University 

 Experiment Station, Berkeley, Cal. 



