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



tional reason for believing in the probable wide-spread distribution 

 of proteid-digesting principles throughout the vegetable kingdom. 



The proteid-digesting power* of fresh pineapple juice is something 

 quite remarkable in its intensity ; it is moreover a constant feature 

 and one which admits of easy demonstration. During the past few 

 months great numbers of ripe pineapples have been examined in the 

 svriter's laboratory and in no instance has the juice failed to show 

 marked proteolytic power, as evidenced by its ready solvent action 

 on blood fibrin and other forms of proteid matter. 



In addition to this proteid-digesting power, we have discovered 

 that the juice also possesses in a remarkable degree the power of curd- 

 ling; or clotting milk. Neutralized pineapple juice added to milk 

 warmed at 40° C, quickly brings about a separation of the casein, in 

 the form of a thick clot or curd, the action being apparently exactly 

 analogous to that of the rennet-ferment or rennin. Boiling the neu- 

 tralized juice prior to its addition to the milk prevents this separation 

 of a clot, and hence the action in question must be due to the pres- 

 ence of a rennet-like ferment. This ferment, indeed, we have been 

 able to separate from the juice, together with the proteolytic fer- 

 ment, by saturation of the fluid with ammonium sulphate and with 

 this preparation we have substantiated its milk-curdling properties. 



General character of pineapple juice. 



As is well known, the pineapple is an exceedingly juicy fruit, an 

 average sized one of 1100 grams yielding, after chopping the tissue 

 and subjecting it to sufficient pressure, 600-800 cubic centimeters, 

 or considerably more than half its weight, of juice. As it flows 

 from the press the fluid has a somewhat turbid appearance, not 

 easily removed by filtration through paper, but eventually, as the 

 pores of the paper become somewhat filled up, a perfectly clear 

 yellowish colored filtrate is obtained, of very decided acid reaction 

 and with an average specific gravity of 1043. The acidity is very 

 pronounced, but naturally quite variable, being dependent in part 

 upon the ripeness of the fruit. A determination of the acidity of 

 twenty distinct samples of filtered juice showed an average acidity 

 equivalent to 0-45 per cent, hydrochloric acid (HCl), the extremes 

 being 0'28 per cent, and 0-65 per cent., calculated as HCl. The con- 

 tent of proteid matter in the clear filtered juice is quite small. 

 Heated with Millon's reagent, a fairly strong proteid reaction is 



* This was referred to by the writer in a paper read before the Philadelphia County 

 Medical Society, May 13, 1891, an abstract of which was pubh shed in the Medical 

 News, vol. Iviii, p. 719. 



