DAIRY FARMING DAIRYING. 573 



means of manufacturing and ripening cheeses, and maintains that real tecli- 

 nical study has been almost entirely neglected. 



He has observed that the acidity of milk on being drawn varies considerably 

 (from 7 to 9.6 per cent) among cows under identical conditions. After 20 

 hours at 10° C. the acidity fell from 8 to 7.2 per cent and from 9.6 to 9. This 

 decrease is still further accentuated (an average of 0.9 per cent) by moderately 

 warming the milk during several minutes immediately after drawing. The ad- 

 dition of lactic acid to the milk raises the acidity in almost direct numerical re- 

 lation to the quantity added, and there is nothing to prevent the same effect from 

 the acidity due to fermentation. The author defines the acidity of fermentation 

 as the acidity due to the lactic fermentation and added to the natural acidity. 

 The difference betweeu the acidity of the milk and that of the serum after 

 the coagulation of the casein is practically constant. The diminution is, 

 therefore, due almost entirely to the removal of the casein. 



He has obtained experimental confirmation of the technical principle that the 

 duration of manufacture of Grana cheese is in almost inverse relation to the 

 degree of ripening of the milk. Thus, whilst a milk of Soxhlet acidity 3.S coagu- 

 lates in 30 minutes at 38° and the time of working the Pariuesan obtained 

 is ISO minutes, the same milk coagulates in 18 minutes when one adds (to the 

 quantity necessary to give a cheese) 80 gm. of pure lactic acid, and the period 

 of working is reduced to 60 minutes. 



The addition of 1.5 cc. of normal lactic acid to 120 cc. of fresh milk and 

 submitting it to the process of making Parmesan, together with an equal 

 sample to which no lactic acid had been added, showed that the lactic acid 

 favored a greater expulsion of the serum from the coagulum (which con- 

 tained 48 per cent of water against 55.83) and removed from the coagulum 

 about 2 per cent more of mineral matter (5.3 against 7.23 per cent), repre- 

 sented by phosphate of lime which passed into the serum as soluble phosphate 

 and lactate of lime. The serum contained in the coagulum before scalding 

 increased the percentage of ash (1.91 per cent in the dry coagulum against 1.3 

 per cent in the same coagulum after washing), but at the end of scalding 

 there was no sensible difference between the quantities of ash contained in 

 the coagulum directly dried (2.43 per cent) and in the coagulum previously 

 washed (2.41 per cent). This indicates that, at the end of the scalding, the 

 granules of casein do not give up to the washing water the serum which they 

 contain and form a homogeneous mass. 



The addition to samples of 200 cc. each of the same milk of 10 cc. of dis- 

 tilled water or water containing, respectively, 1, 2, and 3 cc. of normal lactic 

 acid before submission to the Parmesan process showed that the soluble com- 

 pounds of lime and phosphoric acid increase with the degree of acidity of the 

 serum, but the compounds of lime in a greater proportion than those of phos- 

 phoric acid. This indicated that a part of the lime which passes into solution 

 in the serum belongs to a salt different from monocalcium phosphates, namely, 

 lactate of lime. The plasticity acquired by the paracasein in proportion to 

 its freedom from mineral constituents has been specially attributed to the 

 presence of calcium lactate, but this was not confirmed by the author's ex- 

 periments, according to which the elasticity of the paracasein is certainly 

 bound up with the presence of an acid salt, probably monocalcium phosphate. 



It was apparent that Emmental cheese is made under conditions of very 

 low acidity of fermentation, while Grana cheese requires a certain amount of 

 acidity, and Cheddar a much greater acidity. After manufacture, the casein 

 granules should therefore possess very different chemical composition and 



