26 FOOD MATERIALS AND HOW TO DETECT THEM 



12. OILS AND FATS 

 Object. To learn how to recognize oils and fats in foods. 



Apparatus. Olive oil, beef fat, butter, flaxseed meal, castor 

 beans, nuts, unglazed paper, ether, and an evaporating dish. 



Method. Oils and fats may be recognized by the fact 

 that they make a grease spot on unglazed paper. They do 

 not all yield their oil at once, and some require special treat- 

 ment to extract it. 



(a) Contact. Place a drop of olive oil on a piece of un- 

 glazed paper. Result? 



(6) Heat. Place some flaxseed meal on the paper and 

 heat it over a lamp or in an oven. Result ? 



(c) Pressure. Place some flaxseed meal or corn meal on 

 the paper and apply considerable pressure. Result? 



(d) Solution. Place any of these substances in a test 

 tube, add ether, and shake the mixture. Then strain the 

 filtrate and put it in an evaporating dish. Allow it to stand 

 until the ether has evaporated and try the residue on paper 

 for grease spot. On account of its great inflammability ether 

 should not be brought near a burning lamp. 



Note. A grease spot often looks like a wet spot. To tell one 

 from the other, hold the paper over a flame. If it is a grease spot, 

 the spot will spread and remain; but if a wet spot, it will dry out 

 and disappear. 



Some nuts are so rich in oils as to burn like a candle. This 

 is particularly true of the Brazil nut. If the shell is removed and 

 the kernel is held with one end in a lamp flame, it will take fire and 

 burn for a long time, giving a clear white flame and very little smoke. 

 Removal of grease spots from clothing by pressing with hot flat 

 irons on brown paper is an application of a, 6, and c, and the use 

 of gasolene in " dry cleaning " is an application of d. 



