Sept. ii, 1916 Progressive Oxidation of Cold-Storage Butter 



937 



Table III. — Analysis of air extracted from butter made from sweet cream churned imme- 

 diately after the addition of lactic acid 



[Calculated to o" C. and 760 mm. Acidity of cream as lactic acid, 0.71 per cent; salt, 0.S5 per cent; 



curd, 0.55 per cent] 



Number of bacteria per gram. 



2,050 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 

 o. . . . 



Time stored. 



At 0° F. 



Days. 



75 

 104 

 140 

 202 



At 3 2°F. 



Days. 



6 



3 2 

 48 

 62 

 80 



At 



room tem- 

 perature. 



Hours. 



Oxygen. 



Per cent. 

 21. 

 20, 

 16 



14. 



5 



4 



17 



16 



Carbon 

 dioxia. 



Per cent. 



II. 20 

 II.08 

 6.74 

 3.86 

 4-45 

 4-54 

 4.48 

 1.79 

 i-7S 

 i- 54 



Having now determined that the decomposition caused by cream 

 acidity progresses at a temperature of o° F. in a package of butter and 

 can be measured by an analysis of the gas extracted therefrom, the next 

 step in the investigation of the problem concerning the development of 

 "off flavors" in storage butter involved a series of experiments the 

 purpose of which was to determine whether this measurable decomposi- 

 tion occurs in the fat of the butter itself, in the buttermilk, or in both. 



OXIDATION OF PURE BUTTER FAT » 



The butter fat used in the following determinations was prepared to 

 exclude, so far as possible, by melting, filtering, and washing all ingre- 

 dients of the butter other than fat and was made from the same lot of 

 cream as the samples of butter B t and B 2 , mentioned later. The butter 

 was warmed in a glass vessel to from 32 ° to 34 C. and allowed to stand, 

 to separate the fat from the greater part of the nonfatty substances. 

 The supernatant fat was then siphoned off, filtered into water at 12 

 to 14 C, and then thoroughly agitated to granulate it. The fat was then 

 washed several times, salted, and worked on a table worker to the extent 

 of 40 revolutions. The butter fat so prepared was found to contain but 

 0.05 per cent of protein (total NX 6.38). It was packed in absolutely 

 clean and sterile glass jars and also in the special glass tubes for air analy- 



1 The term "pure butter fat " is merely relative. Osbome and Mendel (-) have affirmed that butter fat 

 prepared by centrifugalizing melted butter and pipetting off the clear fat was "entirely free from nitrogen 

 and phosphorus and was devoid of any ash-yiclding or water-soluble components." FunkandMacallum(2) 

 have recently challenged this statement as regards nitrogen, since they find that butter fat prepared accord- 

 ing to Osborne and Mendel's directions yields easily measured quantities of nitrogen in each of the repeated 

 washings with dilute acid and they conclude that it is very difficult and perhaps impossible completely to 

 free butter fat from nitrogenous substances. McCollum and Davis (4) state that their experiments with 

 butter fat tend to strengthen the conclusion drawn by Funk and Macallum regarding the difficulty of 

 completely freeing the butter fat from nitrogen. 



