300 R. H. Chittenden — Ferments of Pineapple Juice. 



Separation of the proteolytic ferment. 



Saturation of neutralized pineapple juice with ammonium sulphate 

 precipitates, as already stated, all of the proteid matter contained in 

 the solution. The filtrate does not give the slightest trace of a tur- 

 bidity on boiling, even after the addition of acetic acid. Nitric acid 

 likewise fails to give any reaction. Acetic acid and potassium fer- 

 rocyanide, however, give a slight flocky precipitate, which does not 

 appear to be composed of proteid matter. The ammonium sulphate 

 precipitate contains all of the proteol^^tic ferment and likewise the 

 milk-curdling ferment, if this is a distinct body. It is readily and 

 completely soluble in water, and by long continued dialysis the 

 solution can be freed from ammonium sulphate. Unless every trace 

 of adherent salt is removed from the solution, the fluid remains 

 fairly clear, but the reaction so far as our experience extends be- 

 comes, almost invariably, slightly alkaline. On evaporation of the 

 fluid, after removal of all, or nearly all of the salt, a scaly residue is 

 obtained readily soluble in water, or in the slight trace of salt 

 present, with strong proteolytic power and giving distinct reactions 

 with the xanthoprotein, biuret and Millon's test. The aqueous 

 solution is usually slightly turbid, the turbidity however disappear- 

 ing on the addition of a little salt-solution, especially with the aid 

 of a gentle heat, also on the addition of 0*2 per cent, hydro- 

 chloric acid. Evidently, the bodies composing the ammonium sul- 

 phate precipitate are readily soluble in very dilute salt-solution, if 

 not in water alone. 



This method constitutes a fairly good way of separating the fer- 

 ments from the bulk of the extraneous matters present in the juice. 

 We have not, however, spent much time in a close study of the make- 

 up of this product as it is obviously a mixture of essentially all the 

 proteid bodies contained in the juice, but it makes a very good 

 preparation with which to demonstrate the proteolytic and milk- 

 curdling properties of the ferments. 



The most satisfactory method we have thus far found for the 

 isolation of the proteolytic ferment, and one which yields a product 

 with very strong digestive power, is by precipitation with common 

 salt. 



Saturation of neuti'alized pineapple juice with sodium chloride 

 gives rise to a small flocculent precipitate, which is not at all in- 

 creased by the addition of acetic acid to the salt-saturated fluid. 

 Obviously, this precipitate might be composed of a globulin, or of a 

 body akin to heteroproteose. It was studied after the following 



