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



The two precipitates produced by heat alone, viz : at V5-78° C. 

 and at 100° C. are not coagulated proteids in the ordinary sense of 

 the term. Unlike an ordinary coagulum of albumin or globulin, 

 these precipitates, when filtered off and washed with water, dis- 

 solve readily and almost entirely in dilute solutions of potassium 

 hj'^droxide ; they are also more or less completely soluble in 0-5 per 

 cent, solution of sodium carbonate, especially if warmed, and are 

 somewhat soluble in 0*2 per cent, hydrochloric acid. In strong 

 nitric acid on the other hand, both precipitates are insoluble unless 

 a large quantity of the acid is added. They are likewise insoluble 

 in 10 per cent, solution of sodium chloride. The proteid separable 

 by heat at about 75° C. appears somewhat more soluble in 0'5 per 

 cent, sodium carbonate than the substance separating at 100° C, the 

 latter dissolving completely in 0"5 per cent, sodium carbonate only 

 when the mixture is heated to boiling. The solution of the above 

 precipitates in dilute alkali is not alkali-albumin, although the sub- 

 stance is in part precipitated by neutralization of the alkaline fluid, 

 since nitric acid gives a precipitate apparently wholly insoluble in 

 excess of the acid, even on heating. 



These two proteids, when dissolved in potassium hydroxide and 

 tested with a few drops of a dilute solution of cupric sulphate, give 

 a violet rather than a red biuret reaction. 



While thus these two proteids precipitated by heat, at 75° and 

 100° C. respectively, ai"e not exactly akin to an ordinary albumin or 

 globulin in their behavior towards heat, neither do they closely 

 resemble on the other hand an ordinary albumose, like the fi phyt- 

 albumose of Martin* present in papaw juice, since the precipitates 

 are not readily soluble in nitric acid, even when heated, and when 

 once dissolved are not separable on cooling the solution. 



As already stated, the amount of proteid matter in pineapple juice 

 is comparatively small and apparently these two proteids, separable 

 by boiling, compose the greater part of the albuminous matter. The 

 amount was determined by simply heating 100'^'= of filtered (acid) juice 

 to boiling, collecting the precipitate on a weighed filter, washing it 

 thoroughl}^ with boiling Avater and drying it at 110° C. until of 

 constant weight. The result showed the presence of only 0-0270 

 gram in the 100°'^ of juice, or less than 0"025 per cent. 



When neutralized pineapple juice is subjected to heat precipita- 

 tion, the initial turbidity makes its appearance at about 72°-74° C. 

 with separation of flocks at 82°-83° C. The filtrate from this pre- 

 * Journal of Physiology, vol. vi, p. 347. 



