282 OIL-CAKES 



largely replacing the older one, especially in America, the solvent is 

 removed by means of steam, and the pressed residue is then ground 

 and sent into the market as oil meal or linseed meal. The new pro- 

 cess meal is richer in protein and carbohydrates, but much poorer in 

 fat. It is also less digestible than the old process meal. 



Properly ripened linseed is free from starch, though the immature 

 seed contains a small quantity. Many weed seeds, perhaps accident- 

 ally mixed with the linseed, are usually rich in starch. As a rule 

 the oil extractor is careful to exclude all foreign matters from the seed 

 because of their retaining the oil, which is very valuable. The presence 

 of starch, therefore, in linseed cake or meal generally indicates adul- 

 teration after the extraction of the oil. 



Occasionally the husks of the castor-oil seed occur in linseed cakes 

 (probably through accident), and such cakes are often poisonous. A 

 method for the detection of such admixture is described by Leather. 1 



As a rule, Russian and English cakes are richest in oil, while the 

 American products excel in nitrogenous compounds. Indian cakes 

 are poorest in albuminoids, and American ones, owing to the higher 

 pressures employed in their manufacture, are deficient in oil. 



A point of some interest is the almost universal occurrence of a 

 cyanogenetic glucoside, linamarin, identical with phaseolunatin, in 

 linseed cake. Fortunately, the hydrolyaing enzyme, capable of liberat- 

 ing hydrocyanic acid from this substance, which is present in the 

 seed, is destroyed by the high temperature employed during the extrac- 

 tion of the oil, so that the cake is rarely, if ever, poisonous from this 

 cause. 2 Indeed, the minute quantities of prussic acid liberated may 

 exert a beneficial, medicinal effect upon the animals. 3 



Linseed cake is, deservedly, one of the most popular feeding stuffs 

 among cattle feeders. 



Cotton-seed cake. For composition of the seed see p. 243. 



Two varieties of cake are made decorticated, in which the envelopes 

 of the seed, with the adhering particles of cotton, are removed before 

 expressing the oil ; and undecorticated, in which the whole seed is sub- 

 jected to hydraulic pressure. The latter is naturally of much less 

 value than the former. 



The " hulls " removed in the process of " decortication " are 

 used locally as food for cattle, but in England are not of much im- 

 portance. 



Decorticated cotton cake is a concentrated and valuable food for 

 all farm animals except pigs and calves. In the case of the animals 

 mentioned, sickness and death have frequently resulted from feeding 

 with cotton cake or meal. The cause of the poisonous effect does not 

 appear to be known, though it has been attributed to choline, which 

 is present in cotton seed. 4 According to Crawford (1910) the toxic 

 effects are due to the presence of salts of pyrophosphoric acid, H 4 P 2 7 . 



Cotton-seed cake, fed to dairy cows, increases the firmness and 

 whiteness of the butter, but if used too freely causes the butter to give 



1 Jour. Koy. Agric. Soc., 1892. 



2 Vide Henry & Auld, Jour. Soc. Chem. Ind., 1908, 428. 



3 Eyre & Armstrong, Brit. Assoc., 1912; Nature, Nov. 14, 1912, 319. 

 Vide p. 212. 



