

THE LOSS OF COLOUR IN WINE 241 



succinic acid. A series of experiments on the behaviour of fifty-two species of 

 bacteria towards twenty-one different organic acids was performed by A. 

 MAASSEN (I.), principally on medical grounds. One result of this research was 

 the discovery of a new characteristic valuable in the bacteriological analysis of 

 water for the differentiation of Bacillus tyj>hi abdominalis from Bacterium coli 

 commune viz., tricarballylic acid, COOH CH 2 CH.COOH CH 8 COOII, 

 which is attacked and partly destroyed by the first-named organism, but is left 

 altogether untouched by the second. 



More minute investigations into the fermentation of the above-named organic 

 acids would be of value, not only in solving the preliminary questions involved in 

 the study of loss of colour in wine, but also in connection with the decrease in 

 the acidity of wines and fruit wines during stora.ge, a phenomenon well known 

 in practice and one quantitatively examined by PAUL BEHREND (I.) and by 

 P. KULISCH (I.). This decrease so long as it remains within narrow limits 

 is looked upon with favour, as contributing to the rounding and improvement of 

 the flavour of the maturing wine. If, however, it proceeds too far and the 

 acidity falls too low, then a proportionate decrease in the power of the beverage 

 to withstand disease (especially loss of colour) ensues. This fermentation of the 

 acids is, as already stated, principally effected by fission fungi, on which point a 

 few particulars have been given by MULLER-THURGAU (V.). To a small extent 

 these acids are consumed by the yeast in the primary fermentation, so that the 

 quantity present in the young wine is less than in the must. Consequently, if 

 the total acidity in the former is found greater than that of the fresh grape-juice 

 and fruit-must, the excess is due to the carbonic acid held in solution. 



Grapes from vines infested with mildew, whereby both development and 

 sugar formation are retarded, yield wine poor in alcohol and consequently of low 

 resisting power. Such wine frequently becomes diseased, and is then known in 

 France as vin mildiouse. Here again bacterial agency is at work, the rod-shaped 

 organisms forming many-jointed chains and reproducing so abundantly, that 

 they finally accumulate as a thick sediment. U. GAYON (II.) regards this malady 

 as identical with that causing the loss of colour, because he identified in vins 

 mildiouses the same volatile acids (acetic and propionic acids) as have been 

 discovered by others, e.g. E. DUCLAUX (XII.), in vins tournes. 



The mannitic fermentation of wine, which presents a certain oppositeness of 

 character to the malady known as loss of colour, will be described now, because 

 otherwise no suitable occasion would arise. This complaint does not wait to 

 attack the finished wine, but even makes its appearance at the stage of primary 

 fermentation. If the surrounding temperature keeps above 30 0., then 

 alcoholic fermentation is confined within narrow limits, and an opportunity is 

 thus afforded for the development of certain species of bacteria which convert 

 the sugar of the must into mannite. Of this hexatomic alcohol there will be 

 produced, according to circumstances, from i to 30 grams per litre of wine, ii* 

 addition to a little acetic acid. A knowledge of this fact is useful to the analytical 

 chemist as well. Attention was first drawn to the mannite content, of Algerian 

 wines in particular, by P. CARLES (II.) in 1891. Figs, as is well known, very 

 often contain considerable quantities of this alcohol ; hence Carles thought that 

 the presence of mannite in any wine indicated adulteration by fig-wine. How- 

 ever, as reported by J. BEHRENS (IV.), the presence of mannite in reliably pure 

 natural wines (e.g. Bordeaux, Chateau- Yquem) had been proved a year previously 

 by Portes and Lafauric ; and very soon afterwards JEGON (I.) showed that in 

 wines of reliable purity, but imperfectly fermented, as much as eight grams of 

 mannite could be found per litre. L. Roos (I.) then proved that this result was 

 due to bacterial activity, a discovery confirmed by U. GAYON and E. DUBOURG (I.), 

 who isolated from such wine a pure culture of a non-motile short-rod fission 



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