M. H. Chittenden — Ferments of Pineapple Juice. 283 



obtained, the intensity of which, however, appears to be due in part 

 to the presence of tyrosin or some related soluble body. 



With acetic acid alone no precipitate is produced, but with acetic 

 acid and potassium ferrocyanide a slight precipitate or turbidity 

 results. With the biuret test, the reaction is in great part vitiated 

 by the large amount of sugar present in the juice, which gives rise to 

 an intense yellowish-brown color on addition of the strong alkali. 



Neutralization of the acid juice with sodium carbonate fails to 

 give any neutralization precipitate whatever, thus showing the 

 absence of acid-albumin. Concentrated nitric acid produces in the 

 clear filtered juice a white precipitate soluble in excess of the acid, 

 the fluid taking on a bright yellow color. 



Fresh pineapple juice filtered clear and Avith average acidity, sub- 

 jected to fractional heat precipitation grows slightly turbid at 

 60-62° C, the turbidity increasing graduallj^ as the temperature is 

 raised until To-'ZS" C, is reached, when a small flocky coagulum 

 results. The filtrate from this coagulum on being further heated 

 shows signs of turbidity at about 82° C, increasing with the rise 

 in temperature, without however any distinct signs of flocking until 

 the boiling point is reached. As the fluid commences to boil, but 

 sometimes only after persistent boiling, a fine flocky precipitate sep- 

 arates, which on filtration leaves a perfectly clear fluid. This fluid, 

 free from all matter coagulable by heat, gives with Millon's reagent 

 the usual proteid reaction, while with acetic acid and potassium fer- 

 rocyanide, it yields a distinct white precipitate. Concentrated nitric 

 acid alone gives no reaction, but addition of saturated-salt solution 

 with the acid causes a distinct turbidity, which is increased rather 

 than diminished by heat. We have thus evidence of the presence in 

 pineapple juice of what appears to be three distinct proteids ; two 

 separable from the acid juice by heat alone, one at about 75° C, the 

 other at 100° C, while the third body is wholly non-coagulable by 

 heat, but is precipitable by acetic acid and potassium ferrocyanide 

 This latter proteid can also be precipitated by saturation of its solu- 

 tion with ammonium sulphate (after removal of the proteids separable 

 by boiling) together with some non-proteid matter present in the 

 juice, and after removal of the ammonium sulphate by dialysis o-ives 

 the reactions above indicated. It is present only in very small 

 quantity. In some cases, however, this thii'd body is j) resent in the 

 juice in larger quantity, or to express it more exactly, in some speci- 

 mens the precipitate produced by acetic acid and potassium fer- 

 rocyanide in the filtrate from the heat precipitations is considerably 

 more pronounced than first described. 



Trans. Conn. Acad., Vol. VIII. 38 Jan., 1892. 



