240 THE PHENOMENA OF PUTREFACTION 



a number of species being essential. In fact, the number of decomposable 

 constituents in unaltered sound wine is so great as to preclude the possibility of 

 a single species effecting all the changes involved. Consequently, investigations 

 on this point will need to be carried out to a somewhat comprehensive scale. 

 Several purely chemical researches into the changes produced were maJe by 

 J. Konig, and abstracts of them are given in BABO and MACK'S (I.) " Handbuch 

 des Weinbaues " (Handbook of Viticulture). Similar researches should now be 

 made with pure cultures of bacteria isolated from wines that have lost their 

 colour, and such researches should also include the examination of the changes 

 produced by the different species of these organisms, in each of the most 

 important constituents of wine. 



This malady is also known as the putrefactive fermentation or " decaying " 

 of wine, from the final condition attained by the liquid. Wines rich in albumen, 

 e.g. even the Hungarian red wines, according to M. PREYSS (I.), are found to 

 have a special tendency to loss of colour. In order to understand why southern 

 wines are so prone to this malady, it is necessary to recall the fact already 

 mentioned in previous chapters, and first quantitatively investigated by 

 N". SIEBER (I.) that putrefaction does not ensue in strongly acid liquids, 

 whereas these wines are poor in acid. FONSECA and CHIAROMONTE (I.) re- 

 commended the addition of citric acid to increase their power of resisting the 

 complaint. The destruction of the acids of wine must therefore precede its final 

 putrefactive fermentation; hence the primary object of research must be the 

 discovery of the changes produced in these acids. Here, again, everything still 

 remains to be done, since all the information at present available is derived 

 almost exclusively from experiments in which pure cultures were not employed. 



According to the discoveries of PASTEUR (IX.) and A. FITZ (IV.), tartaric 

 acid (in the form of its calcium salt) can be decomposed by bacterial agency in 

 three ways : viz., either into propionic acid (along with a little acetic acid) ; to 

 butyric acid ; or, finally, to acetic acid, small quantities of ethyl alcohol, succinic 

 acid, and butyric acid being also produced. Malic acid also may yield very 

 different fermentation products, among which BECHAMP (IV.) mentions acetic 

 acid, propionic acid, butyric acid, carbon dioxide, and hydrogen. According to 

 the researches of A. FITZ (IV.), malic acid (combined with lime) may be split up 

 by different species of ferments in three different ways. In the first case, 

 succinic acid, acetic acid, and carbon dioxide are formed, the relative proportions 

 being approximately represented by the equation 



3COOH CH 2 CH.OH COOH = 2COOH CH 2 CH 2 COOH + 

 CH 3 COOH + 2C0 2 + H a O. 



In a second case, propionic acid, acetic acid, and carbon dioxide may be found ; 

 or, thirdly, butyric acid may be the chief product, along with a small quantity of 

 carbon dioxide. With regard to succinic acid, BECHAMP (V.) asserts that this 

 also may be split up (by a bacterial mixture not more precisely specified) into 

 propionic acid and carbon dioxide, the following equation 



COOH CH 2 CH 2 COOH = CH 3 CILj COOH + C0 2 . 



approximately expressing the reaction. The succeeding homologue of this acid, 

 viz., pyrotartaric acid, breaks up, under similar conditions, into carbon dioxide 

 and methane, according to the equation 



2COOH CHjj CH.CHg COOH + aH 2 = sCH 4 + sC0 2 . 



According to the researches of Fitz, citric acid is converted, by an unspecified 

 bacterial mixture, into acetic acid and small quantities of ethyl alcohol and 



