615 



capacity i'or absorbing moisture from tlie air, or to the removal of large 

 quantities of fat, lor a considerable amount of fat remaining behind in 

 the press-cake may present a mechanical hindrance to the spread of 

 the ferment through the cake. Although the protein content of the 

 press cake is raised by thorough expression of the fat, the cake would 

 then be of less value to the farmer on account of its decreased keeping 

 qualities. 



In general, the ])resence of a large amount of free fatty acids in i)ea- 

 nut cake can not be taken as indicating a spoiled or bad condition. On 

 the contrary, the worst and poorest preserved jx^a-nuts, and in particu- 

 lar those which had a rancid odor, gave a low acid equivalent. 



Directly after the ex[)ressiou of the oil from i>ea-nuts, the fat remain- 

 ing in the press-cake has the same content of free acids as that of the 

 oil in the pea-nuts. This acid content of the fat increases in the pea-nut 

 cake rapidly, but irregularly', so that a determination of the free fatty 

 acids present gives no indication as to the age of the cake, or the con- 

 dition or age of the pea-nuts or from which it was derived. 



Iodine number. — The iodine number, or the expression for the amount 

 of iodine absorbed by fat, is said to furnish an indication of the amount 

 of hypoga'ic acid present in pea-nut oil. According to Benedikt* hypo- 

 gii^ic acid forms white, needle-shaped crystals which when exposed to 

 the air turn brown, forming volatile, rancid-smelling fatty acids. The 

 more hypoga'ic acid lost from peanut oil, then, the lower will be the 

 iodine numlier. The author found that the giyceride of hypoga^ic acid, 

 similar to the acid itself, undergoes changes by which the iodine num- 

 ber is decreased. This fact calls attention to the necessity of drying 

 both the material taken for analysis and the ether extract iu an atmos- 

 l)here of some inditferent gas, to prevent the escape of the giyceride 

 of hypogaMC acid. In several trials in which both ground pea-nuts 

 mixed with sand and the fat extracted from the same were dried in car- 

 bonic acid, hydrogen gas, and air, there was a considerable difference 

 between the iodine number in the materials diied in the air and that 

 dried in the hydrogen gas. The results of determinations of the iodine 

 mimber in the same sample agreed more closely among themselves and 

 were higher where hydrogen was used. In various determinations, the 

 older and poorer the peaiiuts, and the stronger the rancid odor, the 

 lower was the iodine number. The iodine number ranged in the fat of 

 pea-nuts from G2.7 to 98.5, and in that of peanut cakes from 40 to 80.1. 

 The author believes that the iodine equivalent of fat obtained by ex- 

 traction will be little if any lower than that of oil expressed from the 

 same pea-nuts ; and that the determination of the iodine number in fat 

 obtained by extraction under exclusion of oxidizing influences offers a 

 means of judging whether a peanut cake has been made from fresh, 

 good pea-nuts, or whether the fat of the same has undergone changes 

 either iu the manufacturing process or by storing the cake. Press-cake 



* Analyse der Fette, p. 14. 



