736 EXPERIMENT STATION EECOED. 



with the oil the second time. This plan of working the pulp has been sug- 

 gested for commercial use and has been employed with success by one manu- 

 facturer. In commercial practice oil of considerable value is left in the pomace 

 after the last pressing. To decrease this loss the writer suggests that when 

 the pomace is being pressed for the last time, it be made into smaller cheeses 

 separated by gratings from one-half to two-thirds the area of those used for 

 the first pressing. Notes and data are given on the pressing tests of the vari- 

 ous varieties used, together with analyses of olives and a table showing the 

 behavior of olive oils during hot and cold weather. 



As a result of these investigations, the author finds that many varieties of 

 olives, when grown under Arizona conditions, are well adapted to oil making, 

 and that when properly made from them the oil may be of the very finest 

 quality. Of the varieties tested, Mission, Correggiola, Pendulina, Razza, and 

 Nevadillo were best suited for oil making. The recoverable oil content of the 

 Arizona olive compares favorably with that of the California olive. 



Tlie hot weather test indicated that if cleanliness is diligently observed in the 

 manufacture of olive oils, they ai"e no more perishable than many other care- 

 fully prepared food products. The most satisfactory of the oils as to fluidity 

 in cold weather is Mission. Mausanillo oil in particular solidifies easily into a 

 semisolid state on cooling, even at a temperature between 40 and 50° F. 



Contrary to the rather common opinion that the oil secured by the third and 

 fourth pressings of the olive is suitable only for fuel or soap manufacture and 

 that the so-called virgin oil, or first pressing oil, has poorer keeping quali- 

 ties than that from the second pressing, the author found that under the condi- 

 tions of the experiments oil from all the pressings (even up to five pressings) 

 when mixed together did not appreciably lower the quality of the product. 

 Even when thus mixed, practically all of the oils retained their high quality 

 for one year at least under unusually trying temperature conditions. Most of 

 the samples were ready tor market 4 months after date of manufacture, instead 

 of being aged for a year as is commonly done. 



It is concluded that all the oil which it is possible to extract from ripe olives 

 with a pressure of 640 lbs. per square inch may be mixed together with safety, 

 provided all the pressings are made in one day and the oil is not allowed to 

 stand with the black juice more than a few minutes, and very cleanly methods 

 are used. 



The author finds that the acridity so objectionable in oil is chiefly due to the 

 admixture of greer. olives or olives which have matured at one end only. An 

 inspection of a number of soutliwestern oil mills leads him to form the following 

 conclusions as to the cause of the bad flavors sometimes secured : Careless pick- 

 ing wherolty the berries are broken and a [lart of the oil set free, such free oil 

 rapidly absorbing odors from the soil, musty sacks, etc., until pressed, allowing 

 a long time to elapse between picking and pressing, thus allowing mold to de- 

 velop on the broken berries, the use of filthy and rancid press cloths, the fibers 

 of the cloth permitting the oxygen of the air to come into intimate contact with 

 the absorbed oil with consequent rancidity, lack of dispatch in the pressing 

 process and in separating the oil from the black press liquid, and overfiltration. 

 Wherever oil is passed through filter paper in the open it is brought into more 

 or less intimate contact with oxygen, with deleterious effects. Consequently the 

 process of settling and racking should be relied upon as much as possible for 

 the clarification of the oil. 



Scheme for the classification of the races of olives grown in southern 

 Italy, M. Marinucci (Atti. R. 1st. Incorcif/g. Napoli, 6. so:, 60 iWOS). pp. 165- 

 ISO). — This has been previously noted as a sejjarate (E. S. R., 20, p. 1132). 



