216 ORGANIC FOODSTUFFS. 



in young beer are capable of affording nutrition for the further 

 development of yeast has been repeatedly shown, inter alia, by 

 F. HYDE (I.) and HAYDUCK (V., VI.), though it would be erroneous 

 to assume that the whole of these nitrogenous substances are 

 suitable for this purpose, or that any one of them is accessible to 

 any race of yeast. Unfortunately, the observations available on 

 this important question are but few, e.g. those communicated by 

 DELBRUCK (V.). The appearance of yeasty haze in lager beer (see 

 p. 1 86, vol. ii.) and in stored wine may probably be traced by 

 further investigation to wort or must proteids, which the yeast 

 concerned in primary fermentation has been unable to consume, 

 but which during storage has furnished structural material for the 

 development of some other race of yeast that has crept in in the 

 meantime. Wine must also contains an excess of nitrogenous 

 nutriment for the yeast, and left unconsumed by the latter. H. 

 MULLER-THURGAU (II.) took a Geisenheimer Riesling must of 

 1888 vintage, which he subjected to six fermentations in suc- 

 cession, removing the resulting yeast and alcohol arid adding 

 fresh sugar each time, the final result being a wine containing 

 0.051 grm. of nitrogen per 100 c.c., as against o.ioo grm. in the 

 must, whilst the removed yeast contained 0.049 g rm - I* 1 accord- 

 ance with the gradual diminution of nitrogen in the maturing 

 wine, the successive deposits of yeast separated from the super- 

 natant wine also exhibit a diminished nitrogen content. Thus in 

 a case examined by A. CZKH and H. MULLER-THURGAU (I.), the 

 first deposit of yeast furnished 6.19 per cent., and the fourth only 

 4.3 per cent. The course of fermentation in the must is also 

 influenced by the method of treating the vines. MULLER-THURGAU 

 (II.) reported on a case of stormy fermentation in must which, in 

 consequence of the heavy manuring of the vineyard, contained 

 not less than 0.12 percent, of nitrogen. The residue of nitro- 

 genous constituents in the new wine, after the removal of the 

 primary yeast, enables the secondary fermentation to be carried 

 through. 



Apple and pear musts are frequently poor in nitrogenous yeast 

 food, and this is generally the case with berry musts, especially 

 bilberry must ; and for this reason they ferment very sluggishly 

 and incompletely. These defects may be remedied as was first 

 advocated by Nessler and tried by H. Miiller-Thurgau by an 

 addition of 20 grins, of sal ammoniac per hectolitre (about 3 oz. 

 per 100 gallons). Similar results, but at higher cost, can be 

 obtained as was done by R. OTTO (I.) by the use of ammo- 

 nium tartrate or even asparagin. 



It would be incorrect to suppose that the total quantity of 

 nitrogenous matters present in wines or beers already existed as 

 such in the must, wort, or mash. On the contrary, a portion, 

 varying considerably according to the conditions of fermentation, 

 originates in the metabolism of the yeast employed, and is excreted 



