PATS AND THEIR ECONOMICAL USE IN THE HOME. 15 



sibilities owing to the fact that as a result of a long series of labora- 

 tory experiments processes have been discovered by which oils may 

 be transformed into a product of any desired hardness by chemically 

 adding hydrogen to them. This reaction takes place, for instance, 

 when finely divided nickel, hydrogen, and the oil to be hardened 

 are intimately mixed under proper conditions. The nickel does not 

 enter into the composition of the hardened fat, but is removed and 

 used repeatedly in the preparation of other batches. The hard- 

 ened oils are generally white in color, have no appreciable odor or 

 taste, and are less likely to become rancid than the original oil. 

 A number of these fats, marketed under a variety of trade names, 

 have proved popular and appear to be of quite wide application. 

 This hardening process may also be of special value in the future 

 utilization of some oils like the fish oils, which, because of objection- 

 able flavors and odors, are not entirely suited for edible purposes in 

 their natural state. 



NUT BUTTERS. 



Closely related to the nut oils mentioned above (see p. 13) are 

 the nut butters prepared by grinding finely the meats of peanuts, 

 almonds, or other nuts rich in fat, so as to produce an oily mass 

 much like butter in consistency. Peanut butter is by far the most 

 common of the nut butters. It is used chiefly as a filling for sand- 

 wiches, crackers, etc., though it finds some use in cooking. The nut 

 butters can be made at home by grinding the whole nuts; a special 

 nut-butter knife being furnished with some of the meat or food 

 choppers. In addition to containing a large amount of fat, nut 

 butters also contain considerable protein. 



AVOCADO. 



Although its oil is not extracted for food purposes, the avocado, 

 commonly called the alligator pear, a tropical fruit which is becom- 

 ing better known in some of our markets, contains as high as 20 per 

 cent of fat in the edible portion. When used in the diet this must be 

 taken into consideration as a source of fat. 



THE SELECTION OF EDIBLE FATS. 



In the selection of edible fats the principal considerations should 

 be the purpose for which the fat is to be used, quality, price, and 

 individual preference, since the energy which the body derives from 

 different fats is about the same, and all are regarded as wholesome 

 when of good quality. Custom, which influences to a considerable 

 extent the choice of all foods, can, therefore, be subordinated to the 

 more essential consideration of economy. 



