212 EXPEEIMENT STATION RECORD. 



Enzym-chemical studies of Edam cheese ripening', W. Van Dam (Centbl. 

 Bakt. [etc.-\, 2. Aht., 26 U910), No. 6-7, pp. 189-222, figs. 3; Rev. Gen. Lait, 8 

 (1910), Nos. Jt, pp. 73-83: 5, pp. 97-107; 6, pp. 121-131; 7, pp. 1-^5-155; 8, pp. 

 169-178, figs. 3). — These investigations pertain chiefly to the role played by 

 rennet in the ripening of Edam cheese and the degree of acidity of the cheese 

 mass. 



The results of the work indicate that a distinction must be made between the 

 potential degree of acidity (determined by titration) and the real degree (which 

 is found by measuring the hydrogen ion concentration) of the cheese, and that 

 the free acid as determined by various authors does not give the true hydrogen 

 ion concentration. The hydrogen ,ion concentration of Edam cheese was found 

 to range between 0.72 and 1.1 X 10 — ^ which shows the acidy to be much less 

 than was previously supposed. Controlling the acidity by the electrolytic con- 

 Tductivity method showed that when on the press the formation of lactic acid 

 has almost reached its extreme limit, and further that fermentation is hardly 

 noticeable in the press during the first hour, when it suddenly shows mani- 

 festations of activity. 



In regard to the part played by rennet in the cheese ripening process, it is 

 shown that a prepared paracasein calcium preparation was easily digested by 

 rennet and that this rate of digestion is in-oportional to the amount of hydrogen 

 ions present. When various rennet preparations were allowed to act on the 

 paracasein calcium preparation at the same degree of acidity the rates of 

 digestion and coagulation were parallel. Calves' stomach extract (prepared 

 according to Hammarsten's method of weakening the peptic activity with ijiag- 

 nesinm carbonate) when allowed to act on paracasein furnished the same 

 results, showing that paracasein is digested only by chymosin, and that no true 

 reason exists for suspecting the presence of a definite casein enzyni in rennet. 

 Digesting the calves' stomach infusion with 0.2 per cent hydrochloric acid solu- 

 tion also desti'oyed the cheese digesting ])roperty, even with an acidity concen- 

 tration of 1.4 X 10 — ''. The peptic digestion with ordinary rennet was always 

 far behind that of the chymosin digestion. Salt was found to accelerate the 

 digestion of paracasein l)y chymosin. 



The dissolving of the casein, it is shown, does not go on until all the para- 

 casein is digested, there being rather a state of equilibrium maintained at 

 a certain concentration of the cleavage products (peptones and caseoses). 

 Chymosin digested the ]iaracai^ein of aseptic milks, and in cheeses which was 

 stored from IJ to 4 and 8 months the same amounts of soluble nitrogenous 

 substances were present. Here, also, an equilibrium of the concentration of the 

 water-soluble nitrogenous constituents was present. 



From this it is concluded that in the cycle of the ripening process the 

 chymosin first breaks up the paracasein, and that under normal conditions the 

 process would then cease were it not for bacteria or bacterial enzyins which 

 have the power of breaking up these products still further into products which 

 give the cheese the characteristic taste and odor. This process again destroys 

 the equilibrium and thereby the solution of the casein can take place anew. 

 From a chemical-dynamic viewpoint the formation of soluble nitrogenous com- 

 pounds in Edam cheese therefore takes place quickest at the earliest stages of 

 the process and in consequence of the accumulation of caseoses and peptones 

 becomes less as the process goes on. For cheese of various ages a nearly con- 

 stant quantity of these cleavage products is found, whereas the increase of 

 water-soluble nitrogenous compounds slowly progresses. 



The colors employed for foodstuffs, A. Gautier et al., (Ann. Falsif., 3 

 (1910), No. 17, pp. 81-87). — A critical discussion of the various colors employed 

 in the manufacture of foodstuffs. 



