YEAST YEAST POWDERS 777 zenberger remarks, "which is indisputably proved, gives considerable support to the the- ories brought forward bj some men of science as to the transformation of ferments, from one | residuum which when dissolved in acetic acid | showed a composition allied to that of eefln- J lose: carbon, 44-9; hydrogen. 6-7; nitrogen, 0-5; remaining ashes, 1-1. Mitsehetfieh sajs the ashes of beer yeast are thus composed : I :- .: .- i 6-1 4-8 Fie. IB. 9. BMlinouMM nreo- Ac. 10. Mneor m dema, magattftd 2S* <&m- fcnnett i DM*. In this it is seen that the chief constituents are phosphoric acid and potash, and a calculation of the state in which all the elements are . bined may be made as follows : to another, according to the conditions under which they are placed,"' Tbe classification of Reess as given above is not accepted on all hands, for the chief reason just given, that it has been observed that yeast fungi appear to have the property of changing into a variety of forms. Thus Dr. W. B. Carpenter ("The Microscope and its Revelations,*' London, 1874) says : " It would appear that yeast may be produced by sowing in a liquid favorable to its development the spornles of any of the ordinary moulds, such as ptnifillium glau- eum, mueor. or aspergillu*, provided the tem- perature be kept up to blood heat; and this even though the solution has been previously heated to 284 F., a temperature which must kill any germs it may itself contain." Prof. J. Cienkowski has made a series of experi- ments on the development of mycodtrma tint, in which he finds that the white pellicle which forms on the surface of various organic fluids, as urine, beer, milk, fruit juice, and encumber juice, consists principally of two ingredients, myeodtrma rini and mdium laeti** the special ferment of milk. (See '* Quarterly Journal of Microscopical Science," April, 1875.) The chemical composition of yeast is remarkable from its large amount of nitrogen. Careful analyses by Schlossberger give the following for the two varieties of beer yeast :
- Galenm phocgfate
41-5 3 1C' 9 2-S 5 fc-8 - ' C-r- - . , Hydrogen. mnwm.. 81-4 45-0 9-3 857 8-5 An analysis by Mulder of the organic elements without the ashes gives a composition nearly allied to albumen: carbon, 53-3; hydrogen, 7*0 ; nitrogen, 16'0. There are probably, there- fore, one or more albuminoid substances in the yeast cell, in which it resembles other vegeta- ble cells. An analysis by Schloasberger. in which he treated the yeast with a weak solu- tion of potash, did not give a result which so nearly agreed with albumen, but he obtained a These analyses have a strong resemblance, par- ticularly in albuminoid elements, to those ob- tained with mushrooms and other fungi. The elaborate experiments of Boussinganlt show that ordinary plants have the power to efimi- , nate nitrogen from its saline compounds, the nitrates, and the question has arisen whether yeast has the same power. The experiments of Dnbrunfant lead to the affirmative, while those of Ad. Mayer give a negative indication. The experiments of Pasteur, in which he sup- I plied the growing yeast with a solution of pure I sugar, to which were added aaaaaaam tar- trate and the ashes of yeast (containing phos- phates i, go to show that the *""" salt slowly yields its nitrogen, which is trans- | formed into albuminoid matter, while the phosphates contained in the ashes furnish min- eral matter to the new phut. But according to the observations of M. Cloez it is possible ' that ammoniacal salts are gradually trans- formed, before the nitrogen is appropriated, into nitrates : this idea agrees with the ordi- narv phenomena of nitrification, and it has been found that, although yeast may decom- pose ammoniacal compounds, its own more natural nitrogenous aliment is contained in the juices of plants. M. Pasteur maintains the ab- solute dependence of the development of yeast upon the presence of alkaline phosphates; hot the statement was disputed by Liebig. who contended that other conditions of M. Pasteur's experiments prevented development. 1E4ST PQWMZS, or EatiK Pw*n, substi- tutes for yeast, used in making bread. The chief object of the use of yeast in bread is to develop carbonic acid gas in the dough, by which bubbles are formed in it and give ft lightness. By many this process is preferred, as any decomposition of the floor is avoided. Some* of the carbonates of the alkalies are commonly used for the purpose. Bicarbonate
