368 Scientific Proceedings, Royal Dublin Society. 



A more complete examination was made of the extract. It gave 274 for the 

 Polenske figure, which estimates the insoluble volatile fatty acids, and 299 for 

 the Kirschner value, which is stated to correspond to the butyric acid. The 

 average values for butter of the above Reiehert-Wollny number are : Polenske 

 3-1, and Kirschner 260. When the diit'usion had gone on for two months there 

 were 27 grams of residue. Accordingly, allowing for 16 per cent, of water, 

 48 per cent, of the butter difEused into the paper at 20° C, and thus the 

 extract constituted nearly 60 per cent, of the butter-fat. Correspondence 

 between the two analyses is therefore to be expected. The numbers show, how- 

 ever, that the percentage of the butyric acid is higher than in butter, though 

 they do not indicate that all the butyric acid is contained in the extract. In 

 combination with the iodine values already given, they would accord with the 

 view that the diffusing oil consisted in a great part of fats of a constitution 

 similar to the butyro-palmito-olein meiitioned by Amberger. 



The interest of these experiments does not lie so much in the information 

 they yield on the actual fats present in butter, which cannot be in any degree 

 exact, but more in their relation to the churning tempei'ature and consequent 

 texture of butter. According to Hunziker the churning temperature may vary 

 within wide limits, possibly from 5°-24° C. In the northern and central part 

 of the dairy region in the United States the variations are eonfhied within much 

 narrower limits, 9°-12° C. in summer, 13°-21° C. in winter. In Ireland it is 

 found desirable to cool the cream as low as 2-2° C, and b'egin churning at 67° C. 

 The presence in Irish butter of a large qiiantity of a constituent solidifying only 

 when cooled below 12° C. indicates the importance of low-cooling in Irish 

 creamery practice to give the fat globules sufficient firmness before churning. 

 Experiments require, however, to be made on a much larger scale, and over a 

 long period to carry out the separation of the fats in sufficient quantity to 

 determine their physical properties or their chemical composition. 



StJMMARY. 



The grease ring formed around butter when placed on paper has been 

 investigated, using fat-free filter-paper. The fat which diffused into the 

 paper was extracted with ether. When the diffusion took place at 20° C, the 

 extract was an oil solidifying between 10° and 12°, and liquefying about 19° C. 

 In comparison with butter it contained a higher percentage of butyric acid, and 

 also of unsaturated fatty acids. Almost 50 per cent, of the content of a sample 

 of Irish butter diffused into paper at this temperature. At 10° C. the diffusion 

 from butter was extremely slow, and the oil obtained had an iodine value 

 corresponding to triolein. The small amount obtained and the slowness of the 

 diffusion are in agreement with the work of Amberger, who estimated the 

 percentage of olein present in butter as not more than 3 per cent. 



REPERENCES. 



1. Blyth and Robertson. — Proc. Chem. Soc. 1889. 



2. Amberger. — Zeitsch. nahr. Genussm. 1918. 35, pp. 313-380. 



3. Brownlee.— Journal Dept. of Agr., Ireland. V. 10. 1910. 

 3. Droop-Richmond. — Dairy Chemistry. 1914. 



5. HuNZKER.— The Butter Industry. 1920. 



