292 HORTICULTURE FOR SCHOOLS 



the end that these may be utilized exclusively in vinegar 

 production. The use of these pure cultures will without 

 doubt result in a superior product. 



Vinegar is commonly manufactured by the quick method. 

 Vats are filled with beech-wood shavings, over which grain 

 alcohol diluted with vinegar is allowed to trickle. This in- 

 troduces bacteria throughout the shavings. A substance 

 containing alcohol, such as hard cider, which is to be trans- 

 formed into vinegar, is then allowed to percolate through 

 these vats. As it does so, the alcohol is acted on by the 

 bacteria and changed into vinegar, which is drawn off at the 

 bottom of the vats. 



405. Olive oil. The olive is a fruit the poor grade of 

 which can be used to excellent advantage in the preparation 

 of a product of considerable commercial importance. Olive 

 oil has been used by man from the time of earliest recorded 

 history and remains today one of the important commercial 

 products. 



The oil is extracted from the pulp by a two-fold process of 

 crushing and pressing. The crushing was done formerly by 

 means of a crude grinder operated by animal power. At the 

 present time, the fruit is first partially dried and then 

 crushed by power-operated rollers. The pulp is inclosed in 

 layers of stout cloth and placed on a hydraulic press. 



The first oil which comes off the press is a high-grade com- 

 mercial product used only for the fancy trade. As pressing 

 continues, the oil becomes poorer in quality and commands a 

 correspondingly lower figure on the market. With present 

 facilities, a considerable part of the oil still remains un- 

 extracted from the pulp, a circumstance which calls for an 

 intensive study of the whole problem. Since that part 

 which is extracted has a very considerable value in the 

 aggregate, and since by this means the poorer grades of fruit 

 are utilized, the industry is one of genuine economic 

 significance. 



