CONCENTRATED FOODS 275 



and there is reason to believe that others may have occurred 

 previously. 



The glucoside was named " linamarin " l by Jorissen, the 

 discoverer, but it was subsequently found to be identical with 

 the phaseolunatin of Java beans previously referred to. The 

 substance itself is said to be harmless, but on maceration with 

 water it undergoes decomposition as shown in the following 

 equation : 



Ci Hn0 6 N + H 2 -> C 6 H 12 O 6 + (CH 3 ) 2 CO + HCN 



(Glucoside.) (Dextrose.) (Acetone.) (Prussic acid.) 



The change is caused by a coexistent, specific enzyme, and 

 it takes place most rapidly at or about the temperature of 

 animal bodies. When heated to 100 C., the enzyme is 

 destroyed or rendered permanently inactive; and as this 

 generally forms part of the ordinary process of manufacture 

 of linseed cakes (vide supra), no danger is to be apprehended. 

 In some cases, however, the seed is pressed cold, or at a lower 

 temperature,, and a certain risk attends the use of cakes made 

 in this way. 



The quantity of potential prussic acid in linseed cakes varies 

 from o up to about 0*05 per cent. It is estimated that about 

 one-third of a pound of the cake containing the maximum 

 amount would poison a sheep, and that from 2 to 3 Ibs. would 

 poison an ox. Cakes containing the maximum quantity 

 mentioned above are, however, comparatively rare, and 

 authenticated cases of poisoning by linseed cake are few. 

 Even if the hydrolytic enzyme be not entirely destroyed in 

 the process of manufacture, it has been found that most other 

 foods, e.g. hay, green fodders, molasses, salt, etc., tend to 

 inhibit its action, but those which contain yeast, malt, or 

 moulds, tend to promote the action. 



The risk of prussic acid poisoning is much greater when 

 whole linseed or linseed meal from which the oil has been 

 extracted by means of solvents at a low temperature are used. 

 In these cases the enzyme is not destroyed, and when they 

 are masticated or made into a mash or gruel with warm water, 

 the conditions are very favourable to its action. Such gruel 

 1 Auld, Report of Chem. Dept. S.E. Agricultural College, Wye, 1912. 



