ALCOHOLS AND ESTERS. 509 



compounds of butyric acid and the other higher fatty acids. The 

 distillation of wine yeasts furnishes, according to PELOUZE and 

 LIEBIG (I.), cenanthic ether, which later investigations have shown 

 to consist chiefly of ethyl caprinate. In addition to traces of 

 other esters, it is also said, by DELFFS (I.), to contain ethyl 

 pelargonate, and by A. FISCHER (I.) capricates and caprylates. 

 According to Liebig, 40,000 parts of wine furnish i part of 

 cenanthic ether, to which the characteristic odour of wine is 

 principally due. 



WORTMANN (XVI.) and MASTBAUM (I.) assert that the bouquet 

 principles may be divided into four classes : ( i ) those originating 

 in the raw materials ; (2) those produced during the saccharin cation 

 of the mash and during fermentation ; (3) those formed during 

 storage; and (4) those generated by distillation. The discussion 

 of the first group does not come within the scope of the present 

 chapter, although the substances concerned possess special im- 

 portance in connection with the bouquet of wine and the character 

 of many beers (hops). The odorous substances formed during 

 fermentation are the above-mentioned esters of the alcohols and 

 fatty acids, all of which are volatile. Some of these substances, 

 the cause of the bouquet of wine, seem to be still unidentified, 

 chemically. Some yeasts, notably LINDNER'S (XLII.) fruity-ether 

 yeasts, produce large quantities of esters, chiefly acetic ether. In 

 addition to these volatile bouquet principles with which should 

 be classed the fruity-smelling neutral ethyl succinate certain 

 non-volatile esters occur in wine, and probably also in beer. 

 According to K. WINDISCH (V.) these esters contribute largely to 

 the flavour of wine. They include acid ethyl succinate, and the 

 fermentation esters of tartaric acid and malic acid, both of which 

 acids exist, ready formed, in the grape. In addition to the 

 primary bouquet principles in the sense adopted by KOSUTANY 

 (II.) and WORTMANN (XVI.) introduced by the grapes themselves, 

 various odorous substances are produced by the different yeasts. 

 On this point compare KOSUTANY (II ), MACH and PoRTELE(IIL), 

 and PICHI (II.). 



The bouquet principles developed during the storage and 

 ripening of wine appear to result principally from the influence of 

 oxygen (see p. 503, vol. ii.). CHOUARD(!.) found that a bouquet prin- 

 ciple formed during primary fermentation; disappeared afterwards, 

 probably as a result of some reducing process in fermentation ; 

 the bouquet may, however, reappear during storage, in consequence 

 of oxidation. According to WORTMANN (VII.), the processes 

 involved in this case are physiological, and not merely chemical 

 reactions. 



Changes, apart from continued fermentation, also occur during 

 the storage of beer; these, according to NATHAN (II,), relating 

 chiefly to the elimination of immature bouquet principles which 

 impart an unripe flavour to the beer. 



